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  • 1.
    Ala-Lahti, Matti
    et al.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Pulkkinen, Tuija I.
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI 48109 USA.;Aalto Univ, Dept Elect & Nanoengn Engn, Espoo, Finland..
    Good, Simon W.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Turc, Lucile
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Kilpua, Emilia K. J.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Transmission of an ICME Sheath Into the Earth's Magnetosheath and the Occurrence of Traveling Foreshocks2021In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 126, no 12, article id e2021JA029896Article in journal (Refereed)
    Abstract [en]

    The transmission of a sheath region driven by an interplanetary coronal mass ejection into the Earth's magnetosheath is studied by investigating in situ magnetic field measurements upstream and downstream of the bow shock during an ICME sheath passage on 15 May 2005. We observe three distinct intervals in the immediate upstream region that included a southward magnetic field component and are traveling foreshocks. These traveling foreshocks were observed in the quasi-parallel bow shock that hosted backstreaming ions and magnetic fluctuations at ultralow frequencies. The intervals constituting traveling foreshocks in the upstream survive transmission to the Earth's magnetosheath, where their magnetic field, and particularly the southward component, was significantly amplified. Our results further suggest that the magnetic field fluctuations embedded in an ICME sheath may survive the transmission if their frequency is below ∼0.01 Hz. Although one of the identified intervals was coherent, extending across the ICME sheath and being long-lived, predicting ICME sheath magnetic fields that may transmit to the Earth's magnetosheath from the upstream at L1 observations has ambiguity. This can result from the strong spatial variability of the ICME sheath fields in the longitudinal direction, or alternatively from the ICME sheath fields developing substantially within the short time it takes the plasma to propagate from L1 to the bow shock. This study demonstrates the complex interplay ICME sheaths have with the Earth's magnetosphere when passing by the planet.

  • 2.
    Ala-Lahti, Matti
    et al.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Kilpua, Emilia K. J.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Soucek, Jan
    Czech Acad Sci, Inst Atmospher Phys, Prague, Czech Republic.
    Pulkkinen, Tuija, I
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI 48109 USA;Aalto Univ, Sch Elect Engn, Espoo, Finland.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Alfven Ion Cyclotron Waves in Sheath Regions Driven by Interplanetary Coronal Mass Ejections2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 6, p. 3893-3909Article in journal (Refereed)
    Abstract [en]

    We report on a statistical analysis of the occurrence and properties of Alfven ion cyclotron (AIC) waves in sheath regions driven by interplanetary coronal mass ejections (ICMEs). We have developed an automated algorithm to identify AIC wave events from magnetic field data and apply it to investigate 91 ICME sheath regions recorded by the Wind spacecraft. Our analysis focuses on waves generated by the ion cyclotron instability. AIC waves are observed to be frequent structures in ICME-driven sheaths, and their occurrence is the highest in the vicinity of the shock. Together with previous studies, our results imply that the shock compression has a crucial role in generating wave activity in ICME sheaths. AIC waves tend to have their frequency below the ion cyclotron frequency, and, in general, occur in plasma that is stable with respect to the ion cyclotron instability and has lower ion beta(parallel to) than mirror modes. The results suggest that the ion beta anisotropy beta(perpendicular to)/beta(parallel to) > 1 appearing in ICME sheaths is regulated by both ion cyclotron and mirror instabilities.

  • 3.
    Ala-Lahti, Matti M.
    et al.
    Univ Helsinki, Dept Phys, POB 64, Helsinki, Finland.
    Kilpua, Emilia K. J.
    Univ Helsinki, Dept Phys, POB 64, Helsinki, Finland.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Aalto Univ, Sch Elect Engn, Espoo, Finland.
    Osmane, Adnane
    Aalto Univ, Sch Elect Engn, Espoo, Finland.
    Pulkkinen, Tuija
    Aalto Univ, Sch Elect Engn, Espoo, Finland.
    Soucek, Jan
    Czech Acad Sci, Inst Atmospher Phys, Prague, Czech Republic.
    Statistical analysis of mirror mode waves in sheath regions driven by interplanetary coronal mass ejection2018In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 36, no 3, p. 793-808Article in journal (Refereed)
    Abstract [en]

    We present a comprehensive statistical analysis of mirror mode waves and the properties of their plasma surroundings in sheath regions driven by interplanetary coronal mass ejection (ICME). We have constructed a semi-automated method to identify mirror modes from the magnetic field data. We analyze 91 ICME sheath regions from January 1997 to April 2015 using data from the Wind spacecraft. The results imply that similarly to planetary magnetosheaths, mirror modes are also common structures in ICME sheaths. However, they occur almost exclusively as dip-like structures and in mirror stable plasma. We observe mirror modes throughout the sheath, from the bow shock to the ICME leading edge, but their amplitudes are largest closest to the shock. We also find that the shock strength (measured by Alfven Mach number) is the most important parameter in controlling the occurrence of mirror modes. Our findings suggest that in ICME sheaths the dominant source of free energy for mirror mode generation is the shock compression. We also suggest that mirror modes that are found deeper in the sheath are remnants from earlier times of the sheath evolution, generated also in the vicinity of the shock.

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  • 4.
    Allen, R. C.
    et al.
    Johns Hopkins Appl Phys Lab, Laurel, MD 20723 USA..
    Cernuda, I
    Univ Alcala De Henares, Space Res Grp, Madrid, Spain..
    Pacheco, D.
    Christian Albrechts Univ Kiel, Inst Expt & Angewande Phys, D-24118 Kiel, Germany..
    Berger, L.
    Christian Albrechts Univ Kiel, Inst Expt & Angewande Phys, D-24118 Kiel, Germany..
    Xu, Z. G.
    Christian Albrechts Univ Kiel, Inst Expt & Angewande Phys, D-24118 Kiel, Germany..
    von Forstner, J. L. Freiherr
    Christian Albrechts Univ Kiel, Inst Expt & Angewande Phys, D-24118 Kiel, Germany..
    Rodriguez-Pacheco, J.
    Univ Alcala De Henares, Space Res Grp, Madrid, Spain..
    Wimmer-Schweingruber, R. F.
    Christian Albrechts Univ Kiel, Inst Expt & Angewande Phys, D-24118 Kiel, Germany..
    Ho, G. C.
    Johns Hopkins Appl Phys Lab, Laurel, MD 20723 USA..
    Mason, G. M.
    Johns Hopkins Appl Phys Lab, Laurel, MD 20723 USA..
    Vines, S. K.
    Johns Hopkins Appl Phys Lab, Laurel, MD 20723 USA..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Horbury, T.
    Imperial Coll, London, England..
    Maksimovic, M.
    Univ Paris Diderot, Observ Paris, Sorbonne Univ, CNRS,LESIA,Univ PSL, Sorbonne Paris Cite,5 Pl Jules Janssen, F-92195 Meudon, France..
    Hadid, L. Z.
    Univ Paris Saclay, Observ Paris, Sorbonne Univ, Ecole Polytech,CNRS,LPP, Paris, France..
    Volwerk, M.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Sorriso-Valvo, Luca
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. CNR ISTP Ist Sci & Tecnol Plasmi, Via Amendola 122-D, I-70126 Bari, Italy..
    Stergiopoulou, Katerina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Andrews, G. B.
    Johns Hopkins Appl Phys Lab, Laurel, MD 20723 USA..
    Angelini, V
    Imperial Coll, London, England..
    Bale, S. D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.;Univ Calif Berkeley, Phys Dept, Berkeley, CA 94720 USA..
    Boden, S.
    Christian Albrechts Univ Kiel, Inst Expt & Angewande Phys, D-24118 Kiel, Germany.;DSI Datensicherheit GmbH, Rodendamm 34, D-28816 Stuhr, Germany..
    Boettcher, S. , I
    Chust, T.
    Univ Paris Saclay, Observ Paris, Sorbonne Univ, Ecole Polytech,CNRS,LPP, Paris, France..
    Eldrum, S.
    Christian Albrechts Univ Kiel, Inst Expt & Angewande Phys, D-24118 Kiel, Germany..
    Espada, P. P.
    Univ Alcala De Henares, Space Res Grp, Madrid, Spain..
    Lara, F. Espinosa
    Univ Alcala De Henares, Space Res Grp, Madrid, Spain..
    Evans, V
    Imperial Coll, London, England..
    Gomez-Herrero, R.
    Univ Alcala De Henares, Space Res Grp, Madrid, Spain..
    Hayes, J. R.
    Johns Hopkins Appl Phys Lab, Laurel, MD 20723 USA..
    Hellin, A. M.
    Univ Alcala De Henares, Space Res Grp, Madrid, Spain..
    Kollhoff, A.
    Christian Albrechts Univ Kiel, Inst Expt & Angewande Phys, D-24118 Kiel, Germany..
    Krasnoselskikh, V
    CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France..
    Kretzschmar, M.
    CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France.;Univ Orleans, Orleans, France..
    Kuehl, P.
    Christian Albrechts Univ Kiel, Inst Expt & Angewande Phys, D-24118 Kiel, Germany..
    Kulkarni, S. R.
    Christian Albrechts Univ Kiel, Inst Expt & Angewande Phys, D-24118 Kiel, Germany.;Deutsch Elektronen Synchrotron DESY, Platanenallee 6, D-15738 Zeuthen, Germany..
    Lees, W. J.
    Johns Hopkins Appl Phys Lab, Laurel, MD 20723 USA..
    Lorfevre, E.
    CNES, Toulouse, France..
    Martin, C.
    Christian Albrechts Univ Kiel, Inst Expt & Angewande Phys, D-24118 Kiel, Germany.;German Aerosp Ctr, Dept Extrasolar Planets & Atmospheres, Berlin, Germany..
    O'Brien, H.
    Imperial Coll, London, England..
    Plettemeier, D.
    Tech Univ Dresden, Dresden, Germany..
    Polo, O. R.
    Univ Alcala De Henares, Space Res Grp, Madrid, Spain..
    Prieto, M.
    Univ Alcala De Henares, Space Res Grp, Madrid, Spain..
    Ravanbakhsh, A.
    Christian Albrechts Univ Kiel, Inst Expt & Angewande Phys, D-24118 Kiel, Germany.;Max Planck Inst Solar Syst Res, Gottingen, Germany..
    Sanchez-Prieto, S.
    Univ Alcala De Henares, Space Res Grp, Madrid, Spain..
    Schlemm, C. E.
    Johns Hopkins Appl Phys Lab, Laurel, MD 20723 USA..
    Seifert, H.
    Johns Hopkins Appl Phys Lab, Laurel, MD 20723 USA..
    Soucek, J.
    Czech Acad Sci, Inst Atmospher Phys, Prague, Czech Republic..
    Steller, M.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Stverak, S.
    Czech Acad Sci, Astron Inst, Prague, Czech Republic..
    Terasa, J. C.
    Christian Albrechts Univ Kiel, Inst Expt & Angewande Phys, D-24118 Kiel, Germany..
    Travnicek, P.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.;Czech Acad Sci, Astron Inst, Prague, Czech Republic..
    Tyagi, K.
    Johns Hopkins Appl Phys Lab, Laurel, MD 20723 USA.;Univ Colorado, LASP, Boulder, CO 80309 USA..
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Royal Inst Technol, Sch Elect Engn & Comp Sci, Dept Space & Plasma Phys, Stockholm, Sweden..
    Vecchio, A.
    Univ Paris Diderot, Observ Paris, Sorbonne Univ, CNRS,LESIA,Univ PSL, Sorbonne Paris Cite,5 Pl Jules Janssen, F-92195 Meudon, France.;Radboud Univ Nijmegen, Res Inst Math Astrophys & Particle Phys, Nijmegen, Netherlands..
    Yedla, M.
    Christian Albrechts Univ Kiel, Inst Expt & Angewande Phys, D-24118 Kiel, Germany.;Max Planck Inst Solar Syst Res, Gottingen, Germany..
    Energetic ions in the Venusian system: Insights from the first Solar Orbiter flyby2021In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 656, article id A7Article in journal (Refereed)
    Abstract [en]

    The Solar Orbiter flyby of Venus on 27 December 2020 allowed for an opportunity to measure the suprathermal to energetic ions in the Venusian system over a large range of radial distances to better understand the acceleration processes within the system and provide a characterization of galactic cosmic rays near the planet. Bursty suprathermal ion enhancements (up to similar to 10 keV) were observed as far as similar to 50R(V) downtail. These enhancements are likely related to a combination of acceleration mechanisms in regions of strong turbulence, current sheet crossings, and boundary layer crossings, with a possible instance of ion heating due to ion cyclotron waves within the Venusian tail. Upstream of the planet, suprathermal ions are observed that might be related to pick-up acceleration of photoionized exospheric populations as far as 5R(V) upstream in the solar wind as has been observed before by missions such as Pioneer Venus Orbiter and Venus Express. Near the closest approach of Solar Orbiter, the Galactic cosmic ray (GCR) count rate was observed to decrease by approximately 5 percent, which is consistent with the amount of sky obscured by the planet, suggesting a negligible abundance of GCR albedo particles at over 2 R-V. Along with modulation of the GCR population very close to Venus, the Solar Orbiter observations show that the Venusian system, even far from the planet, can be an effective accelerator of ions up to similar to 30 keV. This paper is part of a series of the first papers from the Solar Orbiter Venus flyby.

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  • 5.
    Blanco-Cano, Xochitl
    et al.
    Univ Nacl Autonoma Mexico, Inst Geofis, Mexico City, DF, Mexico..
    Battarbee, Markus
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Turc, Lucile
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland..
    Kilpua, Emilia K. J.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Hoilijoki, Sanni
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Ganse, Urs
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Sibeck, David G.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Cassak, Paul A.
    West Virginia Univ, Dept Phys & Astron, Morgantown, WV USA..
    Fear, Robert C.
    Univ Southampton, Dept Phys & Astron, Southampton, Hants, England..
    Jarvinen, Riku
    Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.;Finnish Meteorol Inst, Helsinki, Finland..
    Juusola, Liisa
    Univ Helsinki, Dept Phys, Helsinki, Finland.;Finnish Meteorol Inst, Helsinki, Finland..
    Pfau-Kempf, Yann
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Vainio, Rami
    Univ Turku, Dept Phys & Astron, Turku, Finland..
    Palmroth, Minna
    Univ Helsinki, Dept Phys, Helsinki, Finland.;Finnish Meteorol Inst, Helsinki, Finland..
    Cavitons and spontaneous hot flow anomalies in a hybrid-Vlasov global magnetospheric simulation2018In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 36, no 4, p. 1081-1097Article in journal (Refereed)
    Abstract [en]

    In this paper we present the first identification of foreshock cavitons and the formation of spontaneous hot flow anomalies (SHFAs) with the Vlasiator global magnetospheric hybrid-Vlasov simulation code. In agreement with previous studies we show that cavitons evolve into SHFAs. In the presented run, this occurs very near the bow shock. We report on SHFAs surviving the shock crossing into the down-stream region and show that the interaction of SHFAs with the bow shock can lead to the formation of a magnetosheath cavity, previously identified in observations and simulations. We report on the first identification of long-term local weakening and erosion of the bow shock, associated with a region of increased foreshock SHFA and caviton formation, and repeated shock crossings by them. We show that SHFAs are linked to an increase in suprathermal particle pitch-angle spreads. The realistic length scales in our simulation allow us to present a statistical study of global caviton and SHFA size distributions, and their comparable size distributions support the theory that SHFAs are formed from cavitons. Virtual spacecraft observations are shown to be in good agreement with observational studies.

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  • 6.
    Boldu O Farrill Treviño, Joan Jordi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Morooka, Michiko
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Soucek, J.
    Pisa, D.
    Maksimovic, M.
    Ion-acoustic waves associated with interplanetary shocks2023In: Article in journal (Other academic)
  • 7.
    Boynton, R. J.
    et al.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England.
    Aryan, H.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England; Univ Calif Los Angeles, Dept Atmospher & Ocean Sci, Los Angeles, CA USA.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Balikhin, M. A.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England.
    System Identification of Local Time Electron Fluencies at Geostationary Orbit2020In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 125, no 11, article id e2020JA028262Article in journal (Refereed)
    Abstract [en]

    The electron fluxes at geostationary orbit measured by Geostationary Operational Environmental Satellite (GOES) 13, 14, and 15 spacecraft are modeled using system identification techniques. System identification, similar to machine learning, uses input-output data to train a model, which can then be used to provide forecasts. This study employs the nonlinear autoregressive moving average exogenous technique to deduce the electron flux models. The electron fluxes at geostationary orbit are known to vary in space and time, making it a spatiotemporal system, which complicates the modeling using system identification/machine learning approach. Therefore, the electron flux data are binned into 24 magnetic local time (MLT), and a separate model is developed for each of the 24 MLT bins. MLT models are developed for six of the GOES 13, 14, and 15 electron flux energy channels (75 keV, 150 keV, 275 keV, 475 keV, >800 keV, and >2 MeV). The models are assessed on separate test data by prediction efficiency (PE) and correlation coefficient (CC) and found these to vary by MLT and electron energy. The lowest energy of 75 keV at the midnight sector had a PE of 36.0 and CC of 59.3, which increased on the dayside to a PE of 66.9 and CC of 81.6. These metrics increased to the >2 MeV model, which had a low PE and CC of 63.0 and 81.8 on the nightside to a high of 80.3 and 90.8 on the dayside.

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  • 8.
    Branduardi-Raymont, G.
    et al.
    Univ Coll London, Mullard Space Sci Lab, Holmbury St Mary, Dorking RH5 6NT, Surrey, England..
    Berthomier, M.
    Lab Phys Plasmas, Paris, France..
    Bogdanova, Y. V.
    Rutherford Appleton Lab, Didcot, Oxon, England..
    Carter, J. A.
    Univ Leicester, Leicester, Leics, England..
    Collier, M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dunlop, M.
    Rutherford Appleton Lab, Didcot, Oxon, England.;Beihang Univ, Sch Space & Environm, Beijing, Peoples R China..
    Fear, R. C.
    Univ Southampton, Southampton, Hants, England..
    Forsyth, C.
    Univ Coll London, Mullard Space Sci Lab, Holmbury St Mary, Dorking RH5 6NT, Surrey, England..
    Hubert, B.
    Univ Liege, Liege, Belgium..
    Kronberg, E. A.
    Univ Munich, Munich, Germany..
    Laundal, K. M.
    Univ Bergen, Bergen, Norway..
    Lester, M.
    Univ Leicester, Leicester, Leics, England..
    Milan, S.
    Univ Leicester, Leicester, Leics, England..
    Oksavik, K.
    Univ Bergen, Bergen, Norway..
    Ostgaard, N.
    Univ Bergen, Bergen, Norway..
    Palmroth, M.
    Univ Helsinki, Helsinki, Finland..
    Plaschke, F.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Porter, F. S.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Rae, I. J.
    Northumbria Univ, Newcastle Upon Tyne, Tyne & Wear, England..
    Read, A.
    Univ Leicester, Leicester, Leics, England..
    Samsonov, A. A.
    Univ Coll London, Mullard Space Sci Lab, Holmbury St Mary, Dorking RH5 6NT, Surrey, England..
    Sembay, S.
    Univ Leicester, Leicester, Leics, England..
    Shprits, Y.
    German Res Ctr Geosci, Potsdam, Germany..
    Sibeck, D. G.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Walsh, B.
    Boston Univ, Boston, MA 02215 USA..
    Yamauchi, M.
    Swedish Inst Space Phys, Kiruna, Sweden..
    Exploring solar-terrestrial interactions via multiple imaging observers2022In: Experimental astronomy, ISSN 0922-6435, E-ISSN 1572-9508, Vol. 54, no 2-3, p. 361-390Article in journal (Refereed)
    Abstract [en]

    How does solar wind energy flow through the Earth's magnetosphere, how is it converted and distributed? is the question we want to address. We need to understand how geomagnetic storms and substorms start and grow, not just as a matter of scientific curiosity, but to address a clear and pressing practical problem: space weather, which can influence the performance and reliability of our technological systems, in space and on the ground, and can endanger human life and health. Much knowledge has already been acquired over the past decades, particularly by making use of multiple spacecraft measuring conditions in situ, but the infant stage of space weather forecasting demonstrates that we still have a vast amount of learning to do. A novel global approach is now being taken by a number of space imaging missions which are under development and the first tantalising results of their exploration will be available in the next decade. In this White Paper, submitted to ESA in response to the Voyage 2050 Call, we propose the next step in the quest for a complete understanding of how the Sun controls the Earth's plasma environment: a tomographic imaging approach comprising two spacecraft in highly inclined polar orbits, enabling global imaging of magnetopause and cusps in soft X-rays, of auroral regions in FUV, of plasmasphere and ring current in EUV and ENA (Energetic Neutral Atoms), alongside in situ measurements. Such a mission, encompassing the variety of physical processes determining the conditions of geospace, will be crucial on the way to achieving scientific closure on the question of solar-terrestrial interactions.

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  • 9.
    Carter, J. A.
    et al.
    Univ Leicester, Sch Phys & Astron, Planetary Sci Grp, Univ Rd, Leicester LE1 7RH, Leics, England..
    Dunlop, M.
    Rutherford Appleton Lab Space, Sci Technol Facil Council, Didcot, Oxon, England.;Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China.;Minist Ind & Informat Technol, Key Lab Space Environm Monitoring & Informat Proc, Beijing 100017, Peoples R China..
    Forsyth, C.
    UCL, Dept Space & Climate Phys, Mullard Space Sci Lab, Holmbury St Mary, Dorking RH5 6NT, Surrey, England..
    Oksavik, K.
    Birkeland Centre for Space Science, Department of Physics and Technology., University of Bergen, Bergen, Norway;Arctic Geophysics, University Centre in Svalbard, Longyearbyen, Norway.
    Donovon, E.
    Univ Calgary, Dept Phys & Astron, 2500 Univ Dr, Calgary, AB T2N 1N4, Canada..
    Kavanagh, A.
    British Antarct Survey, Cambridge, England..
    Milan, S. E.
    Univ Leicester, Sch Phys & Astron, Planetary Sci Grp, Univ Rd, Leicester LE1 7RH, Leics, England..
    Sergienko, T.
    Swedish Inst Space Phys, Kiruna, Sweden..
    Fear, R. C.
    Univ Southampton, West Highfield Campus, Univ Rd, Southampton SO17 1BJ, Hants, England..
    Sibeck, D. G.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Connors, M.
    Athabasca Univ, Athabasca, AB, Canada..
    Yeoman, T.
    Univ Leicester, Sch Phys & Astron, Planetary Sci Grp, Univ Rd, Leicester LE1 7RH, Leics, England..
    Tan, X.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China..
    Taylor, M. G. G. T.
    European Space Agcy, ESTEC, Noordwijk, Netherlands..
    McWilliams, K.
    Univ Saskatchewan, Saskatoon, SK, Canada..
    Gjerloev, J.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Barnes, R.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Billet, D. D.
    Univ Saskatchewan, Saskatoon, SK, Canada..
    Chisham, G.
    British Antarctic Survey, Cambridge, UK.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Freeman, M. P.
    British Antarct Survey, Cambridge, England..
    Han, D. -S
    Tongji University, Shanghai 200092, China.
    Hartinger, M. D.
    Space Sci Inst, Ctr Space Plasma Phys, 4765 Walnut St Suite B, Boulder, CO 80301 USA..
    Hsieh, S. -YW.
    The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA.
    Hu, Z. -J
    Polar Research Institute of China, Shanghai 200136, China.
    James, M. K.
    Univ Leicester, Sch Phys & Astron, Planetary Sci Grp, Univ Rd, Leicester LE1 7RH, Leics, England..
    Juusola, L.
    Finnish Meteorol Inst FMI, Helsinki, Finland..
    Kauristie, K.
    Finnish Meteorol Inst FMI, Helsinki, Finland..
    Kronberg, E. A.
    Ludwig Maximilian Univ Munich LMU Munich, Dept Earth & Environm Sci Geophys, Theresienstr 41, D-80333 Munich, Germany..
    Lester, M.
    Univ Leicester, Sch Phys & Astron, Planetary Sci Grp, Univ Rd, Leicester LE1 7RH, Leics, England..
    Manuel, J.
    Canadian Space Agcy, Montreal, PQ, Canada..
    Matzka, J.
    GFZ German Res Ctr Geosci, Potsdam, Germany..
    McCrea, I.
    Rutherford Appleton Laboratory Space, Science Technology Facilities Council, Oxfordshire, UK.
    Miyoshi, Y.
    Nagoya Univ, Inst Space Earth Environm Res, Ctr Integrated Data Sci, Nagoya, Aichi 4648601, Japan..
    Rae, J.
    Northumbria Univ, Newcastle Upon Tyne NE1 8ST, Tyne & Wear, England..
    Ren, L.
    Chinese Acad Sci, Natl Space Sci Ctr, Beijing 100190, Peoples R China..
    Sigernes, F.
    Univ Ctr Svalbard, Arct Geophys, Longyearbyen, Norway..
    Spanswick, E.
    Department of Physics and Astronomy, University of Calgary, 2500 University Drive, Calgary, Alberta, Canada T2N 1N4.
    Sterne, K.
    Center for Space Plasma Physics, Space Science Institute, 4765 Walnut Street Suite B, Boulder, Colorado, 80301, USA.
    Steuwer, A.
    EISCAT, Kiruna, Sweden..
    Sun, T.
    Chinese Acad Sci, Natl Space Sci Ctr, Beijing 100190, Peoples R China..
    Walach, M. -T
    Space and Planetary Physics Group, Physics Department, Lancaster University, Lancaster, LA1 4YB, UK.
    Walsh, B.
    Boston Univ, Ctr Space Phys, Boston, MA USA..
    Wang, C.
    Chinese Acad Sci, Natl Space Sci Ctr, Beijing 100190, Peoples R China..
    Weygand, J.
    Univ Calif Los Angeles, Earth Planetary & Space Sci, Los Angeles, CA USA..
    Wild, J.
    Space and Planetary Physics Group, Physics Department, Lancaster University, Lancaster, LA1 4YB, UK.
    Yan, J.
    Chinese Acad Sci, Natl Space Sci Ctr, Beijing 100190, Peoples R China..
    Zhang, J.
    Chinese Acad Sci, Natl Space Sci Ctr, Beijing 100190, Peoples R China..
    Zhang, Q. -H
    Shandong Provincial Key Laboratory of Optical Astronomy;Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University, Weihai Shandong 264209, China.
    Ground-based and additional science support for SMILE2024In: Earth and Planetary Physics, E-ISSN 2096-3955, Vol. 8, no 1, p. 275-298Article in journal (Refereed)
    Abstract [en]

    The joint European Space Agency and Chinese Academy of Sciences Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission will explore global dynamics of the magnetosphere under varying solar wind and interplanetary magnetic field conditions, and simultaneously monitor the auroral response of the Northern Hemisphere ionosphere. Combining these large-scale responses with medium and fine-scale measurements at a variety of cadences by additional ground-based and space-based instruments will enable a much greater scientific impact beyond the original goals of the SMILE mission. Here, we describe current community efforts to prepare for SMILE, and the benefits and context various experiments that have explicitly expressed support for SMILE can offer. A dedicated group of international scientists representing many different experiment types and geographical locations, the Ground-based and Additional Science Working Group, is facilitating these efforts. Preparations include constructing an online SMILE Data Fusion Facility, the discussion of particular or special modes for experiments such as coherent and incoherent scatter radar, and the consideration of particular observing strategies and spacecraft conjunctions. We anticipate growing interest and community engagement with the SMILE mission, and we welcome novel ideas and insights from the solar-terrestrial community.

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  • 10.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.
    Alho, M.
    Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.
    Kallio, Esa
    Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.
    Pope, Simon Alexander
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England.
    Zhang, Tielong
    Harbin Inst Technol, Shenzhen, Peoples R China; Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Kilpua, E.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Pulkkinen, Tuija I.
    Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.
    Futaana, Y.
    Swedish Inst Space Phys, Kiruna, Sweden.
    Coates, Andrew J.
    UCL, Mullard Space Sci Lab, London, England.
    The Response of the Venusian Plasma Environment to the Passage of an ICME: Hybrid Simulation Results and Venus Express Observations2018In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 5, p. 3580-3601Article in journal (Refereed)
    Abstract [en]

    Owing to the heritage of previous missions such as the Pioneer Venus Orbiter and Venus Express, the typical global plasma environment of Venus is relatively well understood. On the other hand, this is not true for more extreme driving conditions such as during passages of interplanetary coronal mass ejections (ICMEs). One of the outstanding questions is how do ICMEs, either the ejecta or sheath portions, impact (1) the Venusian magnetic topology and (2) escape rates of planetary ions? One of the main issues encountered when addressing these problems is the difficulty of inferring global dynamics from single spacecraft obits; this is where the benefits of simulations become apparent. In the present study, we present a detailed case study of an ICME interaction with Venus on 5 November 2011 in which the magnetic barrier reached over 250 nT. We use both Venus Express observations and hybrid simulation runs to study the impact on the field draping pattern and the escape rates of planetary O+ ions. The simulation showed that the magnetic field line draping pattern around Venus during the ICME is similar to that during typical solar wind conditions and that O+ ion escape rates are increased by approximately 30% due to the ICME. Moreover, the atypically large magnetic barrier appears to manifest from a number of factors such as the flux pileup, dayside compression, and the driving time from the ICME ejecta.

  • 11.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Gedalin, M.
    Ben Gurion Univ Negev, Dept Phys, Beer Sheva, Israel..
    Lalti, Ahmad
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Trotta, D.
    Imperial Coll London, London, England..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johlander, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Swedish Def Res Agcy, Stockholm, Sweden..
    Vainio, R.
    Univ Turku, Turku, Finland..
    Blanco-Cano, X.
    Univ Nacl Autonoma Mexico, Dept Ciencias Espaciales, Inst Geofis, Ciudad De Mexico, Mexico..
    Kajdic, P.
    Univ Nacl Autonoma Mexico, Dept Ciencias Espaciales, Inst Geofis, Ciudad De Mexico, Mexico..
    Owen, C. J.
    UCL, Mullard Space Sci Lab, London, England..
    Wimmer-Schweingruber, R. F.
    Univ Kiel, Inst Expt & Appl Phys, D-24118 Kiel, Germany..
    Backstreaming ions at a high Mach number interplanetary shock: Solar Orbiter measurements during the nominal mission phase2023In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 679, article id A106Article in journal (Refereed)
    Abstract [en]

    Context: Solar Orbiter, a mission developed by the European Space Agency, explores in situ plasma across the inner heliosphere while providing remote-sensing observations of the Sun. The mission aims to study the solar wind, but also transient structures such as interplanetary coronal mass ejections and stream interaction regions. These structures often contain a leading shock wave that can differ from other plasma shock waves, such as those around planets. Importantly, the Mach number of these interplanetary shocks is typically low (1-3) compared to planetary bow shocks and most astrophysical shocks. However, our shock survey revealed that on 30 October 2021, Solar Orbiter measured a shock with an Alfven Mach number above 6, which can be considered high in this context.

    Aims: Our study examines particle observations for the 30 October 2021 shock. The particles provide clear evidence of ion reflection up to several minutes upstream of the shock. Additionally, the magnetic and electric field observations contain complex electromagnetic structures near the shock, and we aim to investigate how they are connected to ion dynamics. The main goal of this study is to advance our understanding of the complex coupling between particles and the shock structure in high Mach number regimes of interplanetary shocks.

    Methods: We used observations of magnetic and electric fields, probe-spacecraft potential, and thermal and energetic particles to characterize the structure of the shock front and particle dynamics. Furthermore, ion velocity distribution functions were used to study reflected ions and their coupling to the shock. To determine shock parameters and study waves, we used several methods, including cold plasma theory, singular-value decomposition, minimum variance analysis, and shock Rankine-Hugoniot relations. To support the analysis and interpretation of the experimental data, test-particle analysis, and hybrid particle in-cell simulations were used.

    Results: The ion velocity distribution functions show clear evidence of particle reflection in the form of backstreaming ions several minutes upstream. The shock structure has complex features at the ramp and whistler precursors. The backstreaming ions may be modulated by the complex shock structure, and the whistler waves are likely driven by gyrating ions in the foot. Supra-thermal ions up to 20 keV were observed, but shock-accelerated particles with energies above this were not.

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  • 12.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Hietala, H.
    Imperial Coll London, Blackett Lab, London, England.;Univ Turku, Dept Phys & Astron, Turku, Finland.;Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Zou, Y.
    Univ Alabama, Dept Space Sci, Huntsville, AL 35899 USA..
    Compiling Magnetosheath Statistical Data Sets Under Specific Solar Wind Conditions: Lessons Learnt From the Dayside Kinetic Southward IMF GEM Challenge2020In: Earth and Space Science, E-ISSN 2333-5084, Vol. 7, no 6, article id UNSP e2020EA001095Article in journal (Refereed)
    Abstract [en]

    The Geospace Environmental Modelling (GEM) community offers a framework for collaborations between modelers, observers, and theoreticians in the form of regular challenges. In many cases, these challenges involve model-data comparisons to provide wider context to observations or validate model results. To perform meaningful comparisons, a statistical approach is often adopted, which requires the extraction of a large number of measurements from a specific region. However, in complex regions such as the magnetosheath, compiling these data can be difficult. Here, we provide the statistical context of compiling statistical data for the southward IMF GEM challenge initiated by the "Dayside Kinetic Processes in Global Solar Wind-Magnetosphere Interaction" focus group. It is shown that matching very specific upstream conditions can severely impact the statistical data if limits are imposed on several solar wind parameters. We suggest that future studies that wish to compare simulations and/or single events to statistical data should carefully consider at an early stage the availability of data in context with the upstream criteria. We also demonstrate the importance of how specific IMF conditions are defined, the chosen spacecraft, the region of interest, and how regions are identified automatically. The lessons learnt in this study are of wide context to many future studies as well as GEM challenges. The results also highlight the issue where a global statistical perspective has to be balanced with its relevance to more-extreme, less-frequent individual events, which is typically the case in the field of space weather.

  • 13.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Rosenqvist, L.
    Swedish Def Res Agcy, Stockholm, Sweden.
    Hall, J-O
    Swedish Def Res Agcy, Stockholm, Sweden;Swedish Nucl Fuel & Waste Management Co, Solna, Sweden.
    Viljanen, A.
    Finnish Meteorol Inst, Helsinki, Finland.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Honkonen, I
    Finnish Meteorol Inst, Helsinki, Finland.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Sjoberg, E. C.
    Swedish Inst Space Phys, Kiruna, Sweden.
    The GIC and Geomagnetic Response Over Fennoscandia to the 7-8 September 2017 Geomagnetic Storm2019In: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 17, no 7, p. 989-1010Article in journal (Refereed)
    Abstract [en]

    Between 7 and 8 September 2017, Earth experienced extreme space weather events. We have combined measurements made by the IMAGE magnetometer array, ionospheric equivalent currents, geomagnetically induced current (GIC) recordings in the Finnish natural gas pipeline, and multiple ground conductivity models to study the Fennoscandia ground effects. This unique analysis has revealed multiple interesting physical and technical insights. We show that although the 7-8 September event was significant by global indices (Dst similar to 150 nT), it produced an unexpectedly large peak GIC. It is intriguing that our peak GIC did not occur during the intervals of largest geomagnetic depressions, nor was there any clear upstream trigger. Another important insight into this event is that unusually large and rare GIC amplitudes (>10 A) occurred in multiple Magnetic Local Time (MLT) sectors and could be associated with westward and eastward electrojets. We were also successfully able to model the geoelectric field and GIC using multiple models, thus providing a further important validation of these models for an extreme event. A key result from our multiple conductivity model comparison was the good agreement between the temporal features of 1-D and 3-D model results. This provides an important justification for past and future uses of 1-D models at Mantsala which is highly relevant to additional uses of this data set. Although the temporal agreement (after scaling) was good, we found a large (factor of 4) difference in the amplitudes between local and global ground models due to the difference in model conductivities. Thus, going forward, obtaining accurate ground conductivity values are key for GIC modeling.

  • 14.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Rosenqvist, L.
    Swedish Res Def Agcy, Stockholm, Sweden..
    Welling, D. T.
    Univ Texas Arlington, Dept Phys, POB 19059, Arlington, TX 76019 USA..
    Viljanen, A.
    Finnish Meteorol Inst, Helsinki, Finland..
    Honkonen, I.
    Finnish Meteorol Inst, Helsinki, Finland..
    Boynton, R. J.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    On the Regional Variability ofdB/dtand Its Significance to GIC2020In: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 18, no 8, article id e2020SW002497Article in journal (Refereed)
    Abstract [en]

    Faraday's law of induction is responsible for setting up a geoelectric field due to the variations in the geomagnetic field caused by ionospheric currents. This drives geomagnetically induced currents (GICs) which flow in large ground-based technological infrastructure such as high-voltage power lines. The geoelectric field is often a localized phenomenon exhibiting significant variations over spatial scales of only hundreds of kilometers. This is due to the complex spatiotemporal behavior of electrical currents flowing in the ionosphere and/or large gradients in the ground conductivity due to highly structured local geological properties. Over some regions, and during large storms, both of these effects become significant. In this study, we quantify the regional variability ofdB/dtusing closely placed IMAGE stations in northern Fennoscandia. The dependency between regional variability, solar wind conditions, and geomagnetic indices are also investigated. Finally, we assess the significance of spatial geomagnetic variations to modeling GICs across a transmission line. Key results from this study are as follows: (1) Regional geomagnetic disturbances are important in modeling GIC during strong storms; (2)dB/dtcan vary by several times up to a factor of three compared to the spatial average; (3)dB/dtand its regional variation is coupled to the energy deposited into the magnetosphere; and (4) regional variability can be more accurately captured and predicted from a local index as opposed to a global one. These results demonstrate the need for denser magnetometer networks at high latitudes where transmission lines extending hundreds of kilometers are present.

  • 15.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Russell, Christopher T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90095 USA.
    Sagdeev, Roald Z.
    Univ Maryland, Dept Phys, College Pk, MD 20742 USA.
    Krasnoselskikh, Vladimir
    Univ Orleans, CNRS, LPC2E, Orleans, France;Univ Calif Berkeley, Space Sci Lab, 7 Gauss Way, Berkeley, CA 94720 USA.
    Walker, Simon N.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England.
    Carr, Christopher
    Imperial Coll London, London SW7 2AZ, England.
    Dandouras, Iannis
    Univ Toulouse, IRAP, CNRS, UPS,CNES, Toulouse, France.
    Escoubet, C. Philippe
    European Space Agcy, European Space Res & Technol Ctr ESA ESTEC, Noordwijk, Netherlands.
    Ganushkina, Natalia
    Finnish Meteorol Inst, Helsinki, Finland;Univ Michigan, Ann Arbor, MI 48109 USA.
    Gedalin, Michael
    Ben Gurion Univ Negev, Dept Phys, Beer Sheva, Israel.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Aryan, Homayon
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England;NASA Goddard Space Flight Ctr, Greenbelt, MD 20771 USA.
    Pulkkinen, Tuija, I
    Univ Michigan, Ann Arbor, MI 48109 USA;Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.
    Balikhin, Michael A.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England.
    Direct evidence of nonstationary collisionless shocks in space plasmas2019In: Science Advances, E-ISSN 2375-2548, Vol. 5, no 2, article id eaau9926Article in journal (Refereed)
    Abstract [en]

    Collisionless shocks are ubiquitous throughout the universe: around stars, supernova remnants, active galactic nuclei, binary systems, comets, and planets. Key information is carried by electromagnetic emissions from particles accelerated by high Mach number collisionless shocks. These shocks are intrinsically nonstationary, and the characteristic physical scales responsible for particle acceleration remain unknown. Quantifying these scales is crucial, as it affects the fundamental process of redistributing upstream plasma kinetic energy into other degrees of freedom-particularly electron thermalization. Direct in situ measurements of nonstationary shock dynamics have not been reported. Thus, the model that best describes this process has remained unknown. Here, we present direct evidence demonstrating that the transition to nonstationarity is associated with electron-scale field structures inside the shock ramp.

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  • 16.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Welling, D. T.
    Univ Texas Arlington, Dept Phys, POB 19059, Arlington, TX 76019 USA..
    Rosenqvist, L.
    Swedish Def Res Agcy, Stockholm, Sweden..
    Forsyth, C.
    UCL Mullard Space Sci Lab, Dorking, Surrey, England..
    Freeman, M. P.
    British Antarctic Survey, Cambridge, England..
    Rae, I. J.
    UCL Mullard Space Sci Lab, Dorking, Surrey, England.;Northumbria Univ, Newcastle Upon Tyne, Tyne & Wear, England..
    Viljanen, A.
    Finnish Meteorol Inst, Helsinki, Finland..
    Vandegriff, E.
    Univ Texas Arlington, Dept Phys, POB 19059, Arlington, TX 76019 USA..
    Boynton, R. J.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England..
    Balikhin, M. A.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Modeling the Geomagnetic Response to the September 2017 Space Weather Event Over Fennoscandia Using the Space Weather Modeling Framework: Studying the Impacts of Spatial Resolution2021In: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 19, no 5, article id e2020SW002683Article in journal (Refereed)
    Abstract [en]

    We must be able to predict and mitigate against geomagnetically induced current (GIC) effects to minimize socio-economic impacts. This study employs the space weather modeling framework (SWMF) to model the geomagnetic response over Fennoscandia to the September 7-8, 2017 event. Of key importance to this study is the effects of spatial resolution in terms of regional forecasts and improved GIC modeling results. Therefore, we ran the model at comparatively low, medium, and high spatial resolutions. The virtual magnetometers from each model run are compared with observations from the IMAGE magnetometer network across various latitudes and over regional-scales. The virtual magnetometer data from the SWMF are coupled with a local ground conductivity model which is used to calculate the geoelectric field and estimate GICs in a Finnish natural gas pipeline. This investigation has lead to several important results in which higher resolution yielded: (1) more realistic amplitudes and timings of GICs, (2) higher amplitude geomagnetic disturbances across latitudes, and (3) increased regional variations in terms of differences between stations. Despite this, substorms remain a significant challenge to surface magnetic field prediction from global magnetohydrodynamic modeling. For example, in the presence of multiple large substorms, the associated large-amplitude depressions were not captured, which caused the largest model-data deviations. The results from this work are of key importance to both modelers and space weather operators. Particularly when the goal is to obtain improved regional forecasts of geomagnetic disturbances and/or more realistic estimates of the geoelectric field.

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  • 17.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Blanco-Cano, X.
    Univ Nacl Autonoma Mexico, Inst Geofis, Dept Ciencias Espaciales, Ciudad Univ, Ciudad De Mexico, Mexico..
    KajdiC, P.
    Univ Nacl Autonoma Mexico, Inst Geofis, Dept Ciencias Espaciales, Ciudad Univ, Ciudad De Mexico, Mexico..
    Karlsson, T.
    KTH Royal Inst Technol, Sch Elect Engn & Comp Sci, Div Space & Plasma Phys, Stockholm, Sweden..
    Fedorov, A.
    IRAP UPS CNRS, Toulouse, France..
    Owen, C. J.
    UCL, Mullard Space Sci Lab, London, England..
    Werner, Elisabeth
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johlander, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Mirror Mode Storms Observed by Solar Orbiter2022In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 127, no 11, article id e2022JA030754Article in journal (Refereed)
    Abstract [en]

    Mirror modes (MMs) are ubiquitous in space plasma and grow from pressure anisotropy. Together with other instabilities, they play a fundamental role in constraining the free energy contained in the plasma. This study focuses on MMs observed in the solar wind by Solar Orbiter (SolO) for heliocentric distances between 0.5 and 1 AU. Typically, MMs have timescales from several to tens of seconds and are considered quasi-MHD structures. In the solar wind, they also generally appear as isolated structures. However, in certain conditions, prolonged and bursty trains of higher frequency MMs are measured, which have been labeled previously as MM storms. At present, only a handful of existing studies have focused on MM storms, meaning that many open questions remain. In this study, SolO has been used to investigate several key aspects of MM storms: their dependence on heliocentric distance, association with local plasma properties, temporal/spatial scale, amplitude, and connections with larger-scale solar wind transients. The main results are that MM storms often approach local ion scales and can no longer be treated as quasi-magnetohydrodynamic, thus breaking the commonly used long-wavelength assumption. They are typically observed close to current sheets and downstream of interplanetary shocks. The events were observed during slow solar wind speeds and there was a tendency for higher occurrence closer to the Sun. The occurrence is low, so they do not play a fundamental role in regulating ambient solar wind but may play a larger role inside transients.

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  • 18.
    Gedalin, Michael
    et al.
    Bengur Univ Negev, Dept Phys, Beer Sheva, Israel..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Russell, Christopher T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Pogorelov, Nikolai V.
    Univ Alabama Huntsville, Ctr Space Plasma & Aeron Res, Huntsville, AL 35805 USA..
    Roytershteyn, Vadim
    Space Sci Inst, Boulder, CO 80301 USA..
    Role of the overshoot in the shock self-organization2023In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 89, no 2, article id 905890201Article in journal (Refereed)
    Abstract [en]

    A collisionless shock is a self-organized structure where fields and particle distributions are mutually adjusted to ensure a stable mass, momentum and energy transfer from the upstream to the downstream region. This adjustment may involve rippling, reformation or whatever else is needed to maintain the shock. The fields inside the shock front are produced due to the motion of charged particles, which is in turn governed by the fields. The overshoot arises due to the deceleration of the ion flow by the increasing magnetic field, so that the drop of the dynamic pressure should be compensated by the increase of the magnetic pressure. The role of the overshoot is to regulate ion reflection, thus properly adjusting the downstream ion temperature and kinetic pressure and also speeding up the collisionless relaxation and reducing the anisotropy of the eventually gyrotropized distributions.

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  • 19.
    Gedalin, Michael
    et al.
    Ben Gur Univ Negev, Dept Phys, Beer Sheva, Israel..
    Golbraikh, Ephim
    Ben Gur Univ Negev, Dept Phys, Beer Sheva, Israel..
    Russell, Christopher T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Theory Helps Observations: Determination of the Shock Mach Number and Scales From Magnetic Measurements2022In: Frontiers in Physics, E-ISSN 2296-424X, Vol. 10, article id 852720Article in journal (Refereed)
    Abstract [en]

    The Mach number is one of the key parameters of collisionless shocks. Understanding shock physics requires knowledge of the spatial scales in the shock transition layer. The standard methods of determining the Mach number and the spatial scales require simultaneous measurements of the magnetic field and the particle density, velocity, and temperature. While magnetic field measurements are usually of high quality and resolution, particle measurements are often either unavailable or not properly adjusted to the plasma conditions. We show that theoretical arguments can be used to overcome the limitations of observations and determine the Mach number and spatial scales of the low-Mach number shock when only magnetic field data are available.

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  • 20.
    Gedalin, Michael
    et al.
    Ben Gurion Univ Negev, Dept Phys, Beer Sheva, Israel..
    Russell, Christopher T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Shock Mach Number Estimates Using Incomplete Measurements2021In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 126, no 10, article id e2021JA029519Article in journal (Refereed)
    Abstract [en]

    The Mach number is one of the most important parameters of collisionless shocks. The accuracy of its observational determination is compromised by several complications. Incomplete measurements of plasma parameters significantly contribute to the uncertainty, along with the errors of the normal determination. A set of CLUSTER observed shocks is analyzed using several methods for finding the shock normal and to circumvent the shortcomings of the plasma data. A relation between the maximum magnetic compression and the Alfvenic Mach number is established. It is proposed as a proxy for the Mach number estimate when measurements are incomplete.

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  • 21.
    Graham, Daniel B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Lalti, Ahmad
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Boldu, Joan J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Tigik, Sabrina F.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Swedish Inst Space Phys, Uppsala, Sweden..
    Fuselier, S. A.
    Southwest Res Inst, San Antonio, TX USA.;Univ Texas San Antonio, San Antonio, TX USA..
    Ion Dynamics Across a Low Mach Number Bow Shock2024In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 129, no 4, article id e2023JA032296Article in journal (Refereed)
    Abstract [en]

    A thorough understanding of collisionless shocks requires knowledge of how different ion species are accelerated across the shock. We investigate a bow shock crossing using the Magnetospheric Multiscale spacecraft after a coronal mass ejection crossed Earth, which led to solar wind consisting of protons, alpha particles, and singly charged helium ions. The three species are resolved upstream of the shock. The low Mach number of the bow shock enabled the ions to be partly distinguished downstream of the shock due to the relatively low ion heating. Some of the protons are specularly reflected and produce quasi-periodic fine structures in the velocity distribution functions downstream of the shock. Heavier ions are shown to transit the shock without reflection. However, the gyromotion of the heavier ions partially obscures the fine structure of proton distributions. Additionally, the calculated proton moments are unreliable when the different ion species are not distinguished by the particle detector. The need for high time-resolution mass-resolving ion detectors when investigating collisionless shocks is discussed. One of the ongoing challenges when investigating collisionless shocks is determining the energy partition between electromagnetic fields and different particle species. Resolving this question requires detailed observations of the electromagnetic fields and particle distributions, and is challenging when multiple ion species are present. We investigate a crossing of Earth's bow shock for unusual solar wind conditions; three ion species are observed in the solar wind and behind the bow shock, namely protons, alpha particles, and singly charged helium ions. We investigate the ion dynamics and show that a small fraction of protons are reflected by the electric field associated with the shock, which results in complex ion distributions. However, since the highest time-resolution ion detectors cannot distinguish between different ion species, the heavier ions partly obscure the fine structure of the protons. The heavier ions lead to errors when calculating the bulk properties (e.g., moments) of protons. These observations illustrate the need for high time-resolution ion detectors, which can distinguish different ion species when studying shocks. Protons, singly charged helium ions, and alpha particles are observed upstream and downstream of a bow shock crossing The alpha particles and helium ions partly obscure the fine structure of the downstream proton distributions High time-resolution mass-resolving ion detectors are needed to study the ion dynamics across collisionless shocks

  • 22.
    Hadid, L. Z.
    et al.
    PSL Res Univ, LPP, CNRS, Observ Paris,Sorbonne Univ,Ecole Polytech,Inst Po, F-91120 Palaiseau, France..
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Chust, T.
    PSL Res Univ, LPP, CNRS, Observ Paris,Sorbonne Univ,Ecole Polytech,Inst Po, F-91120 Palaiseau, France..
    Pisa, D.
    Czech Acad Sci, Dept Space Phys, Inst Atmospher Phys, Prague, Czech Republic..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Morooka, Michiko
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Maksimovic, M.
    Univ PSL, Sorbonne Univ, Univ Paris, Observ Paris,LESIA,CNRS, Meudon, France..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Soucek, J.
    Czech Acad Sci, Dept Space Phys, Inst Atmospher Phys, Prague, Czech Republic..
    Kretzschmar, M.
    Univ Orleans, CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France..
    Vecchio, A.
    Univ PSL, Sorbonne Univ, Univ Paris, Observ Paris,LESIA,CNRS, Meudon, France.;Radboud Univ Nijmegen, Radboud Radio Lab, Dept Astrophys, Nijmegen, Netherlands..
    Le Contel, O.
    PSL Res Univ, LPP, CNRS, Observ Paris,Sorbonne Univ,Ecole Polytech,Inst Po, F-91120 Palaiseau, France..
    Retino, A.
    PSL Res Univ, LPP, CNRS, Observ Paris,Sorbonne Univ,Ecole Polytech,Inst Po, F-91120 Palaiseau, France..
    Allen, R. C.
    Johns Hopkins Appl Phys Lab, Laurel, MD 20723 USA..
    Volwerk, M.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Fowler, C. M.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Sorriso-Valvo, Luca
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. CNR, Ist Sci & Tecnol Plasmi ISTP, Via Amendola 122-D, I-70126 Bari, Italy..
    Karlsson, T.
    KTH Royal Inst Technol, Space & Plasma Phys, S-10405 Stockholm, Sweden..
    Santolik, O.
    Czech Acad Sci, Dept Space Phys, Inst Atmospher Phys, Prague, Czech Republic.;Charles Univ Prague, Fac Math & Phys, Prague, Czech Republic..
    Kolmasova, I
    Czech Acad Sci, Dept Space Phys, Inst Atmospher Phys, Prague, Czech Republic.;Charles Univ Prague, Fac Math & Phys, Prague, Czech Republic..
    Sahraoui, F.
    PSL Res Univ, LPP, CNRS, Observ Paris,Sorbonne Univ,Ecole Polytech,Inst Po, F-91120 Palaiseau, France..
    Stergiopoulou, Katerina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Moussas, X.
    Natl & Kapodistrian Univ Athens, Dept Astrophys Astron & Mech, Fac Phys, Sch Sci, Zografos 15783, Greece..
    Issautier, K.
    Univ PSL, Sorbonne Univ, Univ Paris, Observ Paris,LESIA,CNRS, Meudon, France..
    Dewey, R. M.
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI 48109 USA..
    Wolt, M. Klein
    Radboud Univ Nijmegen, Radboud Radio Lab, Dept Astrophys, Nijmegen, Netherlands..
    Malandraki, O. E.
    Natl Observ Athens, IAASARS, Metaxa & Vas Pavlou Str, Athens 15236, Greece..
    Kontar, E. P.
    Univ Glasgow, Sch Phys & Astron, Glasgow G12 8QQ, Lanark, Scotland..
    Howes, G. G.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Bale, S. D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.;Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA..
    Horbury, T. S.
    Imperial Coll, Dept Phys, London SW7 2AZ, England..
    Martinovic, M.
    Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA..
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Sch Elect Engn & Comp, Dept Space & Plasma Phys, Stockholm, Sweden..
    Krasnoselskikh, V
    Univ Orleans, CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France..
    Lorfevre, E.
    CNES, 18 Ave Edouard Belin, F-31400 Toulouse, France..
    Plettemeier, D.
    Tech Univ Dresden, Warzburger Str 35, D-01187 Dresden, Germany..
    Steller, M.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Stverak, S.
    Czech Acad Sci, Astron Inst, Prague, Czech Republic.;Czech Acad Sci, Inst Atmospher Phys, Prague, Czech Republic..
    Travnicek, P.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.;Czech Acad Sci, Inst Atmospher Phys, Prague, Czech Republic..
    O'Brien, H.
    Imperial Coll, Dept Phys, London SW7 2AZ, England..
    Evans, V
    Imperial Coll, Dept Phys, London SW7 2AZ, England..
    Angelini, V
    Imperial Coll, Dept Phys, London SW7 2AZ, England..
    Velli, M. C.
    CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA..
    Zouganelis, I
    European Space Agcy ESA, European Space Astron Ctr ESAC, Camino Bajo Castillo S-N, Madrid 28692, Spain..
    Solar Orbiter's first Venus flyby: Observations from the Radio and Plasma Wave instrument2021In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 656, article id A18Article in journal (Refereed)
    Abstract [en]

    Context. On December 27, 2020, Solar Orbiter completed its first gravity assist manoeuvre of Venus (VGAM1). While this flyby was performed to provide the spacecraft with sufficient velocity to get closer to the Sun and observe its poles from progressively higher inclinations, the Radio and Plasma Wave (RPW) consortium, along with other operational in situ instruments, had the opportunity to perform high cadence measurements and study the plasma properties in the induced magnetosphere of Venus.

    Aims. In this paper, we review the main observations of the RPW instrument during VGAM1. They include the identification of a number of magnetospheric plasma wave modes, measurements of the electron number densities computed using the quasi-thermal noise spectroscopy technique and inferred from the probe-to-spacecraft potential, the observation of dust impact signatures, kinetic solitary structures, and localized structures at the bow shock, in addition to the validation of the wave normal analysis on-board from the Low Frequency Receiver.

    Methods. We used the data products provided by the different subsystems of RPW to study Venus' induced magnetosphere.

    Results. The results include the observations of various electromagnetic and electrostatic wave modes in the induced magnetosphere of Venus: strong emissions of similar to 100 Hz whistler waves are observed in addition to electrostatic ion acoustic waves, solitary structures and Langmuir waves in the magnetosheath of Venus. Moreover, based on the different levels of the wave amplitudes and the large-scale variations of the electron number densities, we could identify different regions and boundary layers at Venus.

    Conclusions. The RPW instrument provided unprecedented AC magnetic and electric field measurements in Venus' induced magnetosphere for continuous frequency ranges and with high time resolution. These data allow for the conclusive identification of various plasma waves at higher frequencies than previously observed and a detailed investigation regarding the structure of the induced magnetosphere of Venus. Furthermore, noting that prior studies were mainly focused on the magnetosheath region and could only reach 10-12 Venus radii (R-V) down the tail, the particular orbit geometry of Solar Orbiter's VGAM1, allowed the first investigation of the nature of the plasma waves continuously from the bow shock to the magnetosheath, extending to similar to 70R(V) in the far distant tail region.

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  • 23.
    Hadid, L. Z.
    et al.
    Sorbonne Univ, Inst Polytech Paris, Observ Paris, Lab Phys Plasmas LPP,CNRS,Ecole Polytech,Univ Par, Palaiseau, France..
    Genot, V
    Univ Toulouse, Inst Rech Astrophys & Planetol IRAP, CNES, UPS,CNRS, Toulouse, France..
    Aizawa, S.
    Univ Toulouse, Inst Rech Astrophys & Planetol IRAP, CNES, UPS,CNRS, Toulouse, France..
    Milillo, A.
    Inst Space Astrophys & Planetol IAPS, INAF, Rome, Italy..
    Zender, J.
    ESTEC, European Space Agcy, Noordwijk, Netherlands..
    Murakami, G.
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Sagamihara, Kanagawa, Japan..
    Benkhoff, J.
    ESTEC, European Space Agcy, Noordwijk, Netherlands..
    Zouganelis, I
    European Space Agcy ESA, European Space Astron Ctr ESAC, Madrid, Spain..
    Alberti, T.
    Inst Space Astrophys & Planetol IAPS, INAF, Rome, Italy..
    Andre, N.
    Univ Toulouse, Inst Rech Astrophys & Planetol IRAP, CNES, UPS,CNRS, Toulouse, France..
    Bebesi, Z.
    Wigner Res Ctr Phys, Budapest, Hungary..
    Califano, F.
    Univ Pisa, Dipartimento Fis E Fermi, Pisa, Italy..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dosa, M.
    Wigner Res Ctr Phys, Budapest, Hungary..
    Escoubet, C. P.
    ESTEC, European Space Agcy, Noordwijk, Netherlands..
    Griton, L.
    Univ Toulouse, Inst Rech Astrophys & Planetol IRAP, CNES, UPS,CNRS, Toulouse, France..
    Ho, G. C.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Horbury, T. S.
    Imperial Coll, Blackett Lab, London, England..
    Iwai, K.
    Nagoya Univ, Inst Space Earth Environm Res, Nagoya, Aichi, Japan..
    Janvier, M.
    Univ Paris Saclay, IAS, CNRS, Gif Sur Yvette, France..
    Kilpua, E.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol IRAP, CNES, UPS,CNRS, Toulouse, France.;Univ Bordeaux, Lab Astrophys Bordeaux, CNRS, Pessac, France..
    Madar, A.
    Wigner Res Ctr Phys, Budapest, Hungary..
    Miyoshi, Y.
    Nagoya Univ, Inst Space Earth Environm Res, Nagoya, Aichi, Japan..
    Muller, D.
    ESTEC, European Space Agcy, Noordwijk, Netherlands..
    Pinto, R. F.
    Univ Toulouse, Inst Rech Astrophys & Planetol IRAP, CNES, UPS,CNRS, Toulouse, France.;Univ Paris, Univ Paris Saclay, CNRS INSU, Dept Astrophys AIM,CEA IRFU, Gif Sur Yvette, France..
    Rouillard, A. P.
    Univ Toulouse, Inst Rech Astrophys & Planetol IRAP, CNES, UPS,CNRS, Toulouse, France..
    Raines, J. M.
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI 48109 USA..
    Raouafi, N.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Sahraoui, F.
    Sorbonne Univ, Inst Polytech Paris, Observ Paris, Lab Phys Plasmas LPP,CNRS,Ecole Polytech,Univ Par, Palaiseau, France..
    Sanchez-Cano, B.
    Univ Leicester, Sch Phys & Astron, Leicester, Leics, England..
    Shiota, D.
    Natl Inst Informat & Commun Technol, Koganei, Tokyo, Japan..
    Vainio, R.
    Univ Turku, Dept Phys & Astron, Turku, Finland..
    Walsh, A.
    European Space Agcy ESA, European Space Astron Ctr ESAC, Madrid, Spain..
    BepiColombo's Cruise Phase: Unique Opportunity for Synergistic Observations2021In: Frontiers in Astronomy and Space Sciences, E-ISSN 2296-987X, Vol. 8, article id 718024Article in journal (Refereed)
    Abstract [en]

    The investigation of multi-spacecraft coordinated observations during the cruise phase of BepiColombo (ESA/JAXA) are reported, with a particular emphasis on the recently launched missions, Solar Orbiter (ESA/NASA) and Parker Solar Probe (NASA). Despite some payload constraints, many instruments onboard BepiColombo are operating during its cruise phase simultaneously covering a wide range of heliocentric distances (0.28 AU-0.5 AU). Hence, the various spacecraft configurations and the combined in-situ and remote sensing measurements from the different spacecraft, offer unique opportunities for BepiColombo to be part of these unprecedented multipoint synergistic observations and for potential scientific studies in the inner heliosphere, even before its orbit insertion around Mercury in December 2025. The main goal of this report is to present the coordinated observation opportunities during the cruise phase of BepiColombo (excluding the planetary flybys). We summarize the identified science topics, the operational instruments, the method we have used to identify the windows of opportunity and discuss the planning of joint observations in the future.

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  • 24.
    Hietala, H.
    et al.
    Imperial Coll London, Blackett Lab, London, England.;Univ Turku, Dept Phys & Astron, Space Res Lab, Turku, Finland.;Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90095 USA..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland..
    Zou, Y.
    Univ Alabama, Dept Space Sci, Huntsville, AL 35899 USA..
    Garcia-Sage, K.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    The Challenges and Rewards of Running a Geospace Environment Modeling Challenge2020In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 125, no 3, article id e2019JA027642Article in journal (Other academic)
    Abstract [en]

    Geospace Environment Modeling (GEM) is a community-driven, National Science Foundation-sponsored research program investigating the physics of the Earth's magnetosphere and its coupling to the solar wind and the atmosphere. This commentary provides an introduction to a Special Issue collating recent studies related to a GEM Challenge on kinetic plasma processes in the dayside magnetosphere during southward interplanetary magnetic field conditions. We also recount our experiences of organizing such a collaborative activity, where modelers and observers compare their results, that is, of the human side of bringing researchers together. We give suggestions on planning, managing, funding, and documenting these activities, which provide valuable opportunities to advance the field. Plain Language Summary Geospace Environment Modeling (GEM) is a community-driven, National Science Foundation-sponsored research program investigating the physics of the Earth's magnetosphere and its coupling to the solar wind and the atmosphere. An integral part of the program is the so-called "Challenges", which bring people together to compare models and observations in order to advance our understanding of the near-Earth space environment. This commentary provides an introduction to a Special Issue collating recent studies related to one such collaborative effort. We also share our experiences as early-career scientists organizing such an activity, to aid those who might take part in such endeavors in the future. We give suggestions on planning, managing, funding, and documenting the activities.

  • 25.
    Hoilijoki, S.
    et al.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA;Univ Helsinki, Dept Phys, Helsinki, Finland.
    Ganse, U.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Sibeck, D. G.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Cassak, P. A.
    West Virginia Univ, Dept Phys & Astron, Morgantown, WV 26506 USA.
    Turc, L.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Battarbee, M.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Fear, R. C.
    Univ Southampton, Dept Phys & Astron, Southampton, Hants, England.
    Blanco-Cano, X.
    Univ Nacl Autonoma Mexico, Inst Geofis, Mexico City, DF, Mexico.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Aalto Univ, Dept Elect & Nanoengn, Sch Elect Engn, Espoo, Finland.
    Kilpua, E. K. J.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Jarvinen, R.
    Aalto Univ, Dept Elect & Nanoengn, Sch Elect Engn, Espoo, Finland;Finnish Meteorol Inst, Helsinki, Finland.
    Juusola, L.
    Univ Helsinki, Dept Phys, Helsinki, Finland;Finnish Meteorol Inst, Helsinki, Finland.
    Pfau-Kempf, Y.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Palmroth, M.
    Univ Helsinki, Dept Phys, Helsinki, Finland;Finnish Meteorol Inst, Helsinki, Finland.
    Properties of Magnetic Reconnection and FTEs on the Dayside Magnetopause With and Without Positive IMF Bx Component During Southward IMF2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 6, p. 4037-4048Article in journal (Refereed)
    Abstract [en]

    This paper describes properties and behavior of magnetic reconnection and flux transfer events (FTEs) on the dayside magnetopause using the global hybrid-Vlasov code Vlasiator. We investigate two simulation runs with and without a sunward (positive)B-x component of the interplanetary magnetic field (IMF) when the IMF is southward. The runs are two-dimensional in real space in the noon-midnight meridional (polar) plane and three-dimensional in velocity space. Solar wind input parameters are identical in the two simulations with the exception that the IMF is purely southward in one but tilted 45 degrees toward the Sun in the other. In the purely southward case (i.e., without B-x) the magnitude of the magnetos heath magnetic field component tangential to the magnetopause is larger than in the run with a sunward tilt. This is because the shock normal is perpendicular to the IMF at the equatorial plane, whereas in the other run the shock configuration is oblique and a smaller fraction of the total IMF strength is compressed at the shock crossing. Hence, the measured average and maximum reconnection rate are larger in the purely southward run. The run with tilted IMF also exhibits a north-south asymmetry in the tangential magnetic field caused by the different angle between the IMF and the bow shock normal north and south of the equator. Greater north-south asymmetries are seen in the FTE occurrence rate, size, and velocity as well; FTEs moving toward the Southern Hemisphere are larger in size and observed less frequently than FTEs in the Northern Hemisphere.

  • 26.
    Jebaraj, I. C.
    et al.
    Univ Turku, Dept Phys & Astron, Turku 20500, Finland..
    Dresing, N.
    Univ Turku, Dept Phys & Astron, Turku 20500, Finland..
    Krasnoselskikh, V.
    LPC2E, CNRS, UMR 7328, 3A Ave Rech Sci, Orleans, France.;Univ Calif Berkeley, Space Sci Lab, Berkeley, CA USA..
    Agapitov, O. V.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA USA..
    Gieseler, J.
    Univ Turku, Dept Phys & Astron, Turku 20500, Finland..
    Trotta, D.
    Imperial Coll London, Dept Phys, Blackett Lab, London, England..
    Wijsen, N.
    Katholieke Univ Leuven, Ctr Math Plasma Astrophys, Dept Math, Celestijnenlaan 200B, B-3001 Leuven, Belgium..
    Larosa, A.
    Queen Mary Univ London, Sch Phys & Astron, London, England..
    Kouloumvakos, A.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA..
    Palmroos, C.
    Univ Turku, Dept Phys & Astron, Turku 20500, Finland..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Kolhoff, A.
    Univ Kiel, Inst Expt & Appl Phys, D-24118 Kiel, Germany..
    Kühl, P.
    Univ Kiel, Inst Expt & Appl Phys, D-24118 Kiel, Germany..
    Fleth, S.
    Univ Kiel, Inst Expt & Appl Phys, D-24118 Kiel, Germany..
    Fedeli, A.
    Univ Turku, Dept Phys & Astron, Turku 20500, Finland..
    Valkila, S.
    Univ Turku, Dept Phys & Astron, Turku 20500, Finland..
    Lario, D.
    NASA, Goddard Space Flight Ctr, Heliophys Sci Div, Greenbelt, MD 20771 USA..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vainio, R.
    Univ Turku, Dept Phys & Astron, Turku 20500, Finland..
    Relativistic electron beams accelerated by an interplanetary shock2023In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 680, article id L7Article in journal (Refereed)
    Abstract [en]

    Context: Collisionless shock waves have long been considered to be among the most prolific particle accelerators in the universe. Shocks alter the plasma they propagate through, and often exhibit complex evolution across multiple scales. Interplanetary (IP) traveling shocks have been recorded in situ for over half a century and act as a natural laboratory for experimentally verifying various aspects of large-scale collisionless shocks. A fundamentally interesting problem in both heliophysics and astrophysics is the acceleration of electrons to relativistic energies (> 300 keV) by traveling shocks.

    Aims: The reason for an incomplete understanding of electron acceleration at IP shocks is due to scale-related challenges and a lack of instrumental capabilities. This Letter presents the first observations of field-aligned beams of relativistic electrons upstream of an IP shock, observed thanks to the instrumental capabilities of Solar Orbiter. This study presents the characteristics of the electron beams close to the source and contributes to the understanding of their acceleration mechanism.

    Methods: On 25 July 2022, Solar Orbiter encountered an IP shock at 0.98 AU. The shock was associated with an energetic storm particle event, which also featured upstream field-aligned relativistic electron beams observed 14 min prior to the actual shock crossing. The distance of the beam's origin was investigated using a velocity dispersion analysis (VDA). Peak-intensity energy spectra were anaylzed and compared with those obtained from a semi-analytical fast-Fermi acceleration model.

    Results: By leveraging Solar Orbiter's high temporal resolution Energetic Particle Detector (EPD), we successfully showcase an IP shock's ability to accelerate relativistic electron beams. Our proposed acceleration mechanism offers an explanation for the observed electron beam and its characteristics, while we also explore the potential contributions of more complex mechanisms.

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  • 27.
    Johlander, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Lalti, Ahmad
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Electron Heating Scales in Collisionless Shocks Measured by MMS2023In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 50, no 5, article id e2022GL100400Article in journal (Refereed)
    Abstract [en]

    Electron heating at collisionless shocks in space is a combination of adiabatic heating due to large-scale electric and magnetic fields and non-adiabatic scattering by high-frequency fluctuations. The scales at which heating happens hints to what physical processes are taking place. In this letter, we study electron heating scales with data from the Magnetospheric Multiscale (MMS) spacecraft at Earth's quasi-perpendicular bow shock. We utilize the tight tetrahedron formation and high-resolution plasma measurements of MMS to directly measure the electron temperature gradient. From this, we reconstruct the electron temperature profile inside the shock ramp and find that the electron temperature increase takes place on ion or sub-ion scales. Further, we use Liouville mapping to investigate the electron distributions through the ramp to estimate the deHoffmann-Teller potential and electric field. We find that electron heating is highly non-adiabatic at the high-Mach number shocks studied here.

    Plain Language Summary

    Shock waves appear whenever a supersonic medium, such as a plasma, encounters an obstacle. The plasma, which consists of charged ions and free electrons, is heated by the shock wave through interactions with the electromagnetic fields. In this work, we investigate how electrons are heated at plasma shocks. A key parameter to electron heating is the thickness of the layer where the heating takes place. Here, we use observations from the four Magnetospheric Multiscale spacecraft that regularly cross the standing bow shock that forms when the supersonic plasma, known as the solar wind, encounters Earth's magnetic field. We find that the thickness of the shock is larger than previously reported and is on the scales where ion physics dominate. We also find that the electron heating deviates significantly from simple adiabatic heating.

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  • 28.
    Jung, Jaewoong
    et al.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA.;Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Connor, Hyunju
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Dimmock, Andrew
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Sembay, Steve
    Univ Leicester, Leicester, Leics, England..
    Read, Andrew
    Univ Leicester, Leicester, Leics, England..
    Soucek, Jan
    Acad Sci Czech Republ, Inst Atmospher Phys, Prague, Czech Republic..
    Mshpy23: a user-friendly, parameterized model of magnetosheath conditions2024In: Earth and Planetary Physics, E-ISSN 2096-3955, Vol. 8, no 1, p. 89-104Article in journal (Refereed)
    Abstract [en]

    Lunar Environment heliospheric X-ray Imager (LEXI) and Solar wind−Magnetosphere−Ionosphere Link Explorer (SMILE) will observe magnetosheath and its boundary motion in soft X-rays for understanding magnetopause reconnection modes under various solar wind conditions after their respective launches in 2024 and 2025. Magnetosheath conditions, namely, plasma density, velocity, and temperature, are key parameters for predicting and analyzing soft X-ray images from the LEXI and SMILE missions. We developed a user-friendly model of magnetosheath that parameterizes number density, velocity, temperature, and magnetic field by utilizing the global Magnetohydrodynamics (MHD) model as well as the pre-existing gas-dynamic and analytic models. Using this parameterized magnetosheath model, scientists can easily reconstruct expected soft X-ray images and utilize them for analysis of observed images of LEXI and SMILE without simulating the complicated global magnetosphere models. First, we created an MHD-based magnetosheath model by running a total of 14 OpenGGCM global MHD simulations under 7 solar wind densities (1, 5, 10, 15, 20, 25, and 30 cm−3) and 2 interplanetary magnetic field Bz components (± 4 nT), and then parameterizing the results in new magnetosheath conditions. We compared the magnetosheath model result with THEMIS statistical data and it showed good agreement with a weighted Pearson correlation coefficient greater than 0.77, especially for plasma density and plasma velocity. Second, we compiled a suite of magnetosheath models incorporating previous magnetosheath models (gas-dynamic, analytic), and did two case studies to test the performance. The MHD-based model was comparable to or better than the previous models while providing self-consistency among the magnetosheath parameters. Third, we constructed a tool to calculate a soft X-ray image from any given vantage point, which can support the planning and data analysis of the aforementioned LEXI and SMILE missions. A release of the code has been uploaded to a Github repository.

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  • 29.
    Juusola, Liisa
    et al.
    Finnish Meteorol Inst, Helsinki, Finland..
    Viljanen, Ari
    Finnish Meteorol Inst, Helsinki, Finland..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Swedish Inst Space Phys, Uppsala, Sweden..
    Kellinsalmi, Mirjam
    Finnish Meteorol Inst, Helsinki, Finland..
    Schillings, Audrey
    Umea Univ, Dept Phys, Umea, Sweden..
    Weygand, James M.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Drivers of rapid geomagnetic variations at high latitudes2023In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 41, no 1, p. 13-37Article in journal (Refereed)
    Abstract [en]

    We have examined the most intense external (magnetospheric and ionospheric) and internal (induced) |dH/dt| (amplitude of the 10 s time derivative of the horizontal geomagnetic field) events observed by the high-latitude International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometers between 1994 and 2018. While the most intense external |dH/dt| events at adjacent stations typically occurred simultaneously, the most intense internal (and total) |dH/dt| events were more scattered in time, most likely due to the complexity of induction in the conducting ground. The most intense external |dH/dt| events occurred during geomagnetic storms, among which the Halloween storm in October 2003 featured prominently, and drove intense geomagnetically induced currents (GICs). Events in the prenoon local time sector were associated with sudden commencements (SCs) and pulsations, and the most intense |dH/dt| values were driven by abrupt changes in the eastward electrojet due to solar wind dynamic pressure increase or decrease. Events in the premidnight and dawn local time sectors were associated with substorm activity, and the most intense |dH/dt| values were driven by abrupt changes in the westward electrojet, such as weakening and poleward retreat (premidnight) or undulation (dawn). Despite being associated with various event types and occurring at different local time sectors, there were common features among the drivers of most intense external |dH/dt| values: preexisting intense ionospheric currents (SC events were an exception) that were abruptly modified by sudden changes in the magnetospheric magnetic field configuration. Our results contribute towards the ultimate goal of reliable forecasts of dH/dt and GICs.

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  • 30.
    Kajdic, P.
    et al.
    Univ Nacl Autonoma Mexico, Dept Ciencias Espaciales, Inst Geofis, Ciudad Univ, Ciudad De Mexico, Mexico..
    Pfau-Kempf, Y.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Turc, L.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Palmroth, M.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Takahashi, K.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Kilpua, E.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Soucek, J.
    Acad Sci Czech Republ, Inst Atmospher Phys, Prague, Czech Republic..
    Takahashi, N.
    Univ Tokyo, Dept Earth & Planetary Sci, Grad Sch Sci, Tokyo, Japan..
    Preisser, L.
    Univ Nacl Autonoma Mexico, Dept Ciencias Espaciales, Inst Geofis, Ciudad Univ, Ciudad De Mexico, Mexico.;Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Blanco-Cano, X.
    Univ Nacl Autonoma Mexico, Dept Ciencias Espaciales, Inst Geofis, Ciudad Univ, Ciudad De Mexico, Mexico..
    Trotta, D.
    Univ Calabria, Dipartimento Fis, Cosenza, Italy..
    Burgess, D.
    Queen Mary Univ London, Sch Phys & Astron, London, England..
    ULF Wave Transmission Across Collisionless Shocks: 2.5D Local Hybrid Simulations2021In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 126, no 11, article id e2021JA029283Article in journal (Refereed)
    Abstract [en]

    We study the interaction of upstream ultralow frequency (ULF) waves with collisionless shocks by analyzing the outputs of 11 2D local hybrid simulation runs. Our simulated shocks have Alfvenic Mach numbers between 4.29 and 7.42 and their theta BN angles are 15 degrees, 30 degrees, 45 degrees, and 50 degrees. The ULF wave foreshocks develop upstream of all of them. The wavelength and the amplitude of the upstream waves exhibit a complex dependence on the shock's MA and theta BN. The wavelength positively correlates with both parameters, with the dependence on theta BN being much stronger. The amplitude of the ULF waves is proportional to the product of the reflected beam velocity and density, which also depend on MA and theta BN. The interaction of the ULF waves with the shock causes large-scale (several tens of upstream ion inertial lengths) shock rippling. The properties of the shock ripples are related to the ULF wave properties, namely their wavelength and amplitude. In turn, the ripples have a large impact on the ULF wave transmission across the shock because they change local shock properties (theta BN, strength), so that different sections of the same ULF wavefront encounter shock with different characteristics. Downstream fluctuations do not resemble the upstream waves in terms the wavefront extension, orientation or their wavelength. However, some features are conserved in the Fourier spectra of downstream compressive waves that present a bump or flattening at wavelengths approximately corresponding to those of the upstream ULF waves. In the transverse downstream spectra, these features are weaker.

  • 31.
    Lakka, A.
    et al.
    Aalto Univ, Dept Elect & Nanoengn, Espoo, Finland.
    Pulkkinen, T. I.
    Aalto Univ, Dept Elect & Nanoengn, Espoo, Finland.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Myllys, M.
    Univ Helsinki, Dept Phys, Helsinki, Finland; CNRS, Lab Phys & Chim Environm & Espace, Orleans, France.
    Honkonen, I.
    Finnish Meteorol Inst, Helsinki, Finland.
    Palmroth, M.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    The Cross-Polar Cap Saturation in GUMICS-4 During High Solar Wind Driving2018In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 5, p. 3320-3332Article in journal (Refereed)
    Abstract [en]

    It is well known that the Earth's ionospheric cross‐polar cap potential (CPCP) saturates as a response to the solar wind (SW) driver especially when the level of driving is high and the interplanetary magnetic field is oriented southward. Moreover, previous studies have shown that the upstream Alfvén Mach number may be an important factor in the saturation effect. While the CPCP is often viewed as a measure of the SW‐magnetosphere‐ionosphere coupling, the processes associated with the nonlinearity of the coupling remain an open issue. We use fourth edition of the Grand Unified Magnetosphere‐Ionosphere Coupling Simulation (GUMICS‐4) and artificial SW data to mimic weak and strong driving in order to study the CPCP response to a wide range of interplanetary magnetic field magnitudes (3.5–30 nT) and upstream Alfvén Mach number values (1.2–22). The results provide the first overview of the CPCP saturation in GUMICS‐4 and show that the onset of saturation is strongly dependent on the upstream Alfvén Mach number and the physical processes responsible for the saturation effect might take place both in the Earth's magnetosheath and in the upstream SW.

  • 32.
    Lakka, Antti
    et al.
    Aalto Univ, Dept Elect & Nanoengn, Espoo, Finland.
    Pulkkinen, Tuija I.
    Aalto Univ, Dept Elect & Nanoengn, Espoo, Finland;Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI 48109 USA.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Kilpua, Emilia
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Ala-Lahti, Matti
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Honkonen, Ilja
    Finnish Meteorol Inst, Helsinki, Finland.
    Palmroth, Minna
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Raukunen, Osku
    Univ Turku, Dept Phys & Astron, Turku, Finland.
    GUMICS-4 analysis of interplanetary coronal mass ejection impact on Earth during low and typical Mach number solar winds2019In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 37, no 4, p. 561-579Article in journal (Refereed)
    Abstract [en]

    We study the response of the Earth's magnetosphere to fluctuating solar wind conditions during interplanetary coronal mass ejections (ICMEs) using the Grand Unified Magnetosphere-Ionosphere Coupling Simulation (GUMICS-4). The two ICME events occurred on 15-16 July 2012 and 29-30 April 2014. During the strong 2012 event, the solar wind upstream values reached up to 35 particles cm(-3), speeds of up to 694 km s(-1), and an interplanetary magnetic field of up to 22 nT, giving a Mach number of 2.3. The 2014 event was a moderate one, with the corresponding upstream values of 30 particles cm(-3), 320 km s(-1) and 10 nT, indicating a Mach number of 5.8. We examine how the Earth's space environment dynamics evolves during both ICME events from both global and local perspectives, using well-established empirical models and in situ measurements as references. We show that on the large scale, and during moderate driving, the GUMICS-4 results are in good agreement with the reference values. However, the local values, especially during high driving, show more variation: such extreme conditions do not reproduce local measurements made deep inside the magnetosphere. The same appeared to be true when the event was run with another global simulation. The cross-polar cap potential (CPCP) saturation is shown to depend on the Alfven-Mach number of the upstream solar wind. However, care must be taken in interpreting these results, as the CPCP is also sensitive to the simulation resolution.

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  • 33.
    Lalti, Ahmad
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johlander, A.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Olshevsky, V.
    Main Astronom Observ, Kiev, Ukraine..
    A Database of MMS Bow Shock Crossings Compiled Using Machine Learning2022In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 127, no 8, article id e2022JA030454Article in journal (Refereed)
    Abstract [en]

    Identifying collisionless shock crossings in data sent from spacecraft has so far been done manually or using basic algorithms. It is a tedious job that shock physicists have to go through if they want to conduct case studies or perform statistical studies. We use a machine learning approach to automatically identify shock crossings from the Magnetospheric Multiscale (MMS) spacecraft. We compiled a database of 2,797 shock crossings, spanning a period from October 2015 to December 2020, including various spacecraft-related and shock-related parameters for each event. Furthermore, we show that the shock crossings in the database are spread out in space, from the subsolar point to the far flanks. On top of that, we show that they cover a wide range of parameter space. We also present a possible scientific application of the database by looking for correlations between ion acceleration efficiency at shocks with different shock parameters, such as the angle between the upstream magnetic field and the shock normal theta(Bn) and the Alfvenic Mach number M-A. We find no clear correlation between the acceleration efficiency and M-A; however, we find that quasi-parallel shocks are more efficient at accelerating ions than quasi-perpendicular shocks.

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  • 34.
    Lanabere, Vanina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Rosenqvist, L.
    Swedish Def Res Agcy, Stockholm, Sweden..
    Juusola, L.
    Finnish Meteorol Inst, Helsinki, Finland..
    Viljanen, A.
    Finnish Meteorol Inst, Helsinki, Finland..
    Johlander, A.
    Swedish Def Res Agcy, Stockholm, Sweden..
    Odelstad, E.
    Swedish Def Res Agcy, Stockholm, Sweden..
    Analysis of the Geoelectric Field in Sweden Over Solar Cycles 23 and 24: Spatial and Temporal Variability During Strong GIC Events2023In: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 21, no 12, article id e2023SW003588Article in journal (Refereed)
    Abstract [en]

    Geomagnetic storms can produce large perturbations on the Earth magnetic field. Through complex magnetosphere-ionosphere coupling, the geoelectric field (E) and geomagnetic field (B) are highly perturbed. The E is the physical driver of geomagnetically induced currents. However, a statistical study of the E in Sweden has never been done before. We combined geomagnetic data from the International Monitor for Auroral Geomagnetic Effects network in Northern Europe with a 3-D structure of Earth's electrical conductivity in Sweden as the input of a 1-D model to compute the E between 2000 and 2018. Northwestern Sweden presents statistically larger E magnitudes due to larger |dB/dt| variations in the north than in the south of Sweden and relative lower conductivity in the west compared to central and eastern Sweden. In contrast, the 15 strongest daily maximum |E| events present more frequently a maximum magnitude in central Sweden (62.25 degrees N) and their relative strengths are not the same for all latitudes. These results highlight the different regional response to geomagnetic storms, which can be related to ground conductivity variability and the complex magnetosphere-ionosphere coupling mechanisms. Solar storms represent a major threat to Earth's technology and therefore affect society and the economy. Historically, the main effects were related to electric power grid failures leaving many people without electricity for several hours. In order to prevent this from happening again, it is necessary to understand the temporal and spatial variability of the Earth's electric field in regions where electric power grids are placed. This study combines ground measurements of the magnetic fields in Finland and Estonia and ground conductivity maps in Sweden to estimate the ground electric fields in Sweden. A statistical analysis from 2000 to 2018 shows that the probability to find stronger daily maximum electric field magnitude (|E|) is higher in northwestern Sweden. However, the 15 strongest |E| events were found in the central region of Sweden. Furthermore, 80% of the electric power grid failure reports in Sweden during the period, correspond to events where the strongest daily maximum |E| were observed at 62.25 degrees N. This implies that a better understanding of the local geoelectric field and driving processes are required. The daily maximum geoelectric field magnitude is statistically larger in northwestern Sweden than in central and southern SwedenThe 15 strongest daily maximum geoelectric field events were more frequent in central Sweden than in northern SwedenThe 15 strongest events at each latitude are different, so the geoelectric field presents an important regional variability

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  • 35.
    Ma, Xuanye
    et al.
    Embry Riddle Aeronaut Univ, Daytona Beach, FL 32114 USA..
    Delamere, Peter
    Univ Alaska, Fairbanks, AK USA..
    Nykyri, Katariina
    Embry Riddle Aeronaut Univ, Daytona Beach, FL 32114 USA..
    Otto, Antonius
    Univ Alaska, Fairbanks, AK USA..
    Eriksson, Stefan
    Univ Colorado, Boulder, CO USA..
    Chai, Lihui
    Inst Geol & Geophys, Fairbanks, AK USA..
    Burkholder, Brandon
    Univ Maryland, Baltimore, MD USA.;NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Liou, Yu-Lun
    Embry Riddle Aeronaut Univ, Daytona Beach, FL 32114 USA..
    Kavosi, Shiva
    Embry Riddle Aeronaut Univ, Daytona Beach, FL 32114 USA..
    Density and Magnetic Field Asymmetric Kelvin-Helmholtz Instability2024In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 129, no 3, article id e2023JA032234Article in journal (Refereed)
    Abstract [en]

    The Kelvin-Helmholtz (KH) instability can transport mass, momentum, magnetic flux, and energy between the magnetosheath and magnetosphere, which plays an important role in the solar-wind-magnetosphere coupling process for different planets. Meanwhile, strong density and magnetic field asymmetry are often present between the magnetosheath (MSH) and magnetosphere (MSP), which could affect the transport processes driven by the KH instability. Our magnetohydrodynamics simulation shows that the KH growth rate is insensitive to the density ratio between the MSP and the MSH in the compressible regime, which is different than the prediction from linear incompressible theory. When the interplanetary magnetic field (IMF) is parallel to the planet's magnetic field, the nonlinear KH instability can drive a double mid-latitude reconnection (DMLR) process. The total double reconnected flux depends on the KH wavelength and the strength of the lower magnetic field. When the IMF is anti-parallel to the planet's magnetic field, the nonlinear interaction between magnetic reconnection and the KH instability leads to fast reconnection (i.e., close to Petschek reconnection even without including kinetic physics). However, the peak value of the reconnection rate still follows the asymmetric reconnection scaling laws. We also demonstrate that the DMLR process driven by the KH instability mixes the plasma from different regions and consequently generates different types of velocity distribution functions. We show that the counter-streaming beams can be simply generated via the change of the flux tube connection and do not require parallel electric fields. The growth of Kelvin-Helmholtz (KH) instability is not sensitive to the density asymmetry Magnetic field asymmetry affects KH instability differently during northward and southward interplanetary magnetic field (IMF) conditions Different ion velocity distributions can be generated during northward IMF conditions

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  • 36.
    Ma, Xuanye
    et al.
    Embry Riddle Aeronaut Univ, Dept Phys Sci, Daytona Beach, FL 32114 USA.;Embry Riddle Aeronaut Univ, Ctr Space & Atmospher Res CSAR, Daytona Beach, FL 32114 USA..
    Nykyri, Katariina
    Embry Riddle Aeronaut Univ, Dept Phys Sci, Daytona Beach, FL 32114 USA.;Embry Riddle Aeronaut Univ, Ctr Space & Atmospher Res CSAR, Daytona Beach, FL 32114 USA..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Chu, Christina
    Embry Riddle Aeronaut Univ, Dept Phys Sci, Daytona Beach, FL 32114 USA.;Embry Riddle Aeronaut Univ, Ctr Space & Atmospher Res CSAR, Daytona Beach, FL 32114 USA.;Johns Hopkins Univ, Appl Phys Lab, Baltimore, MD USA..
    Statistical Study of Solar Wind, Magnetosheath, and Magnetotail Plasma and Field Properties: 12+Years of THEMIS Observations and MHD Simulations2020In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 125, no 10, article id e2020JA028209Article in journal (Refereed)
    Abstract [en]

    The solar wind plasma is a major plasma source for the Earth's magnetosphere, which has a strong influence on the magnetotail plasma and field properties. The relative importance of different plasma entry mechanisms and pathways is largely determined by the solar wind conditions. Therefore, the spatial and temporal dependence of magnetotail plasma and field properties under different kinds of solar wind conditions is critically important for understanding the Earth's magnetosphere. This study presents a statistical study of fundamental magnetotail plasma properties in a normalized reference frame by utilizing 12+ years of data from NASA's Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission. These statistical maps are mostly in agreement with the magnetosheath of MHD runs from the CCMC BATS-R-US model, but some features in the maps can be explained by kinetic particle physics, not present in the MHD. The results are also used to investigate the presence of any magnetotail plasma parameter asymmetries and their possible causes. Plain Language Summary Earth's intrinsic magnetic field, generated by the currents in the Earth's interior, protects our planet from solar radiation and plasma called the solar wind. However, physical processes such as magnetic reconnection occurring at the boundary of this magnetic barrier, the magnetosphere, can break this shield, enabling access of solar wind plasma into the Earth's magnetosphere. Earth's ionosphere provides another source for magnetospheric plasma. This plasma can be further accelerated to huge energies, which provides a threat for astronauts and satellites. The effectiveness of physical mechanisms that control the entry and acceleration of this plasma strongly depends on the local magnetic field geometry and plasma properties, which in turn are affected by the solar wind. However, the solar wind properties are not constant but vary as it can originate from different regions of the sun. While the magnetic field of the Sun, the interplanetary magnetic field (IMF), on average forms an "Archimedean Spiral," flapping of the heliospheric current sheet and fluctuations along field lines will make the IMF "hit" the Earth at different orientations, thus impacting the shock geometry in front of the planet, which in turn affects the downstream plasma and field properties in the turbulent boundary layer called the magnetosheath. In this paper, we have characterized the dependence of the large-scale plasma properties in the Earth's magnetosphere and magnetosheath on the solar wind and IMF conditions by using over 12years (thus covering over one solar cycle) of data from NASA's Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission.

  • 37.
    Olshevsky, Vyacheslav
    et al.
    KTH Royal Inst & Technol, Stockholm, Sweden.;Main Astron Observ, Kiev, Ukraine..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Lalti, Ahmad
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Divin, Andrey
    St Petersburg State Univ, St Petersburg, Russia..
    Delzanno, Gian Luca
    Los Alamos Natl Lab, Los Alamos, NM USA..
    Anderzén, Sven
    KTH Royal Inst & Technol, Stockholm, Sweden..
    Herman, Pawel
    KTH Royal Inst & Technol, Stockholm, Sweden..
    Chien, Steven W. D.
    KTH Royal Inst & Technol, Stockholm, Sweden..
    Avanov, Levon
    NASA, Goddard Space Flight Ctr, Greenbelt, ND USA..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Markidis, Stefano
    KTH Royal Inst & Technol, Stockholm, Sweden..
    Automated Classification of Plasma Regions Using 3D Particle Energy Distributions2021In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 126, no 10, article id e2021JA029620Article in journal (Refereed)
    Abstract [en]

    We investigate the properties of the ion sky maps produced by the Dual Ion Spectrometers (DIS) from the Fast Plasma Investigation (FPI). We have trained a convolutional neural network classifier to predict four regions crossed by the Magnetospheric Multiscale Mission (MMS) on the dayside magnetosphere: solar wind, ion foreshock, magnetosheath, and magnetopause using solely DIS spectrograms. The accuracy of the classifier is >98%. We use the classifier to detect mixed plasma regions, in particular to find the bow shock regions. A similar approach can be used to identify the magnetopause crossings and reveal regions prone to magnetic reconnection. Data processing through the trained classifier is fast and efficient and thus can be used for classification for the whole MMS database.

    Plain Language Summary

    Magnetospheric Multiscale Mission (MMS) has been traversing the Earth's magnetosphere to help scientists understand how the tremendous amounts of energy are released through the phenomenon known as magnetic reconnection. The spacecraft can transfer to the Earth only 4% of its measurements due to link limitations. The success of the mission relies on the selection of the most relevant measurement intervals to be sent down to the science operation center. We have trained a small deep convolutional neural network which identifies the kind of plasma the spacecraft is traversing at each measurement interval with an excellent accuracy >98%. We have used our model to identify some of the most interesting regions, bow shocks. It took only a day for the model to process all observations collected by the MMS within 3 years. The model can save a substantial amount of time for the scientists in the loop whose role is to locate such regions manually. The proposed model is suitable for the hierarchy of models being built to fully automate the on-ground data processing. Moreover, it is small enough to be embedded in the on-board software of future missions.

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  • 38.
    Osmane, Adnane
    et al.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Pulkkinen, Tuija, I
    Univ Michigan, Dept Climate & Space Sci, Ann Arbor, MI 48109 USA;Aalto Univ, Sch Elect Engn, Espoo, Finland.
    Jensen-Shannon Complexity and Permutation Entropy Analysis of Geomagnetic Auroral Currents2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 4, p. 2541-2551Article in journal (Refereed)
    Abstract [en]

    In this study we determine whether auroral westward currents can be characterized by low-dimensional chaotic attractors through the use of the complexity-entropy methodology developed by Rosso et al. (2007, https:// doi.org/10.1103/PhysRevLett.99.154102) and based on the permutation entropy developed by Bandt and Pompe (2002, https://doi.org/10.1103/PhysRevLett.88.174102) . Our results indicate that geomagnetic auroral indices are indistinguishable from stochastic processes from time scales ranging from a few minutes to 10 hr and for embedded dimensions d < 8. Our results are inconsistent with earlier studies of Baker et al. (1990, https://doi.org/10.1029/GL017i001p00041), Pavlos et al. (1992), D. Roberts et al. (1991, https://doi.org/10.1029/91GL00021), D. A. Roberts (1991, https://doLorg/10.1029/91JA01088), and Vassiliadis et al. (1990, https://doi.org/10.1029/GL017i011 p01841, 1991, https://doi.org/10.1029/91GL01378) indicating that auroral geomagnetic indices could be reduced to low-dimensional systems with chaotic dynamics.

  • 39.
    Rosenqvist, L.
    et al.
    Swedish Def Res Agcy, Stockholm, Sweden..
    Fristedt, T.
    Multiconsult Norge AS, Dept Marine Technol, Tromso, Norway..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Davidsson, P.
    Swedish Def Res Agcy, Stockholm, Sweden..
    Fridström, R.
    Swedish Def Res Agcy, Stockholm, Sweden..
    Hall, J. O.
    Swedish Def Res Agcy, Stockholm, Sweden..
    Hesslow, L.
    Swedish Def Res Agcy, Stockholm, Sweden..
    Kjäll, J.
    Swedish Def Res Agcy, Stockholm, Sweden..
    Smirnov, M. Yu
    Luleå Univ Technol, Luleå, Sweden..
    Welling, D.
    Univ Texas Arlington, Arlington, TX 76019 USA..
    Wintoft, P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    3D Modeling of Geomagnetically Induced Currents in Sweden-Validation and Extreme Event Analysis2022In: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 20, no 3, article id e2021SW002988Article in journal (Refereed)
    Abstract [en]

    Rosenqvist and Hall (2019), developed a proof-of-concept modeling capability that incorporates a detailed 3D structure of Earth's electrical conductivity in a geomagnetically induced current estimation procedure (GIC-SMAP). The model was verified based on GIC measurements in northern Sweden. The study showed that southern Sweden is exposed to stronger electric fields due to a combined effect of low crustal conductivity and the influence of the surrounding coast. This study aims at further verifying the model in this region. GIC measurements on a power line at the west coast of southern Sweden are utilized. The location of the transmission line was selected to include coast effects at the ocean-land interface to investigate the importance of using 3D induction modeling methods. The model is used to quantify the hazard of severe GICs in this particular transmission line by using historic recordings of strong geomagnetic disturbances. To quantify a worst-case scenario GICs are calculated from modeled magnetic disturbances by the Space Weather Modeling Framework based on estimates for an idealized extreme interplanetary coronal mass ejection. The observed and estimated GIC based on the 3D GIC-SMAP procedure in the transmission line in southern Sweden are in good agreement. In contrast, 1D methods underestimate GICs by about 50%. The estimated GICs in the studied transmission line exceed 100 A for one of 14 historical geomagnetic storm intervals. The peak GIC during the sudden impulse phase of a "perfect" storm exceeds 300 A but depends on the locality of the station as the interplanetary magnetic cloud hits Earth.

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  • 40.
    Sorriso-Valvo, Luca
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. CNR ISTP Ist Sci & Tecnol Plasmi, Via Amendola 122-D, I-70126 Bari, Italy..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Telloni, Daniele
    Natl Inst Astrophys, Astrophys Observ Torino, Via Osservatorio 20, I-10025 Pino Torinese, Italy..
    Turbulent Cascade and Energy Transfer Rate in a Solar Coronal Mass Ejection2021In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 919, no 2, article id L30Article in journal (Refereed)
    Abstract [en]

    Turbulence properties are examined before, during, and after a coronal mass ejection (CME) detected by the Wind spacecraft in 2012 July. The power-law scaling of the structure functions, providing information on the power spectral density and flatness of the velocity, magnetic field, and density fluctuations, were examined. The third-order moment scaling law for incompressible, isotropic magnetohydrodynamic turbulence was observed in the preceding and trailing solar wind, as well as in the CME sheath and magnetic cloud. This suggests that the turbulence could develop sufficiently after the shock, or that turbulence in the sheath and cloud regions was robustly preserved even during the mixing with the solar wind plasma. The turbulent energy transfer rate was thus evaluated in each of the regions. The CME sheath shows an increase of energy transfer rate, as expected from the lower level of Alfvenic fluctuations and suggesting the role of the shock-wind interaction as an additional source of energy for the turbulent cascade.

  • 41.
    Stergiopoulou, Katerina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Halekas, Jasper
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Lester, Mark
    Univ Leicester, Sch Phys & Astron, Leicester, Leics, England..
    Sanchez-Cano, Beatriz
    Univ Leicester, Sch Phys & Astron, Leicester, Leics, England..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Gruesbeck, Jacob R.
    Goddard Space Flight Ctr, Greenbelt, MD USA..
    A Two-Spacecraft Study of Mars' Induced Magnetosphere's Response to Upstream Conditions2022In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 127, no 4, article id e2021JA030227Article in journal (Refereed)
    Abstract [en]

    This is a two-spacecraft study, in which we investigate the effects of the upstream solar wind conditions on the Martian induced magnetosphere and upper ionosphere. We use Mars Express (MEX) magnetic field magnitude data together with interplanetary magnetic field (IMF), solar wind density, and velocity measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, from November 2014 to November 2018. We compare simultaneous observations of the magnetic field magnitude in the induced magnetosphere of Mars (|B|(IM)) with the IMF magnitude (|B|(IMF)), and we examine variations in the ratio |B|(IM)/|B|(IMF) with solar wind dynamic pressure, speed and density. We find that the |B|(IM)/|B|(IMF) ratio in the induced magnetosphere generally decreases with increased dynamic pressure and that a more structured interaction is seen when comparing induced fields to the instantaneous IMF, where reductions in the relative fields at the magnetic pile up boundary (MPB) are more evident than in the field strength itself, along with enhancements in the immediate vicinity of the optical shadow of Mars. We interpret these results as evidence that while the induced magnetosphere is indeed compressed and induced field strengths are higher during periods of high dynamic pressure, a relatively larger amount of magnetic flux threads the region compared to that available from the unperturbed IMF during low dynamic pressure intervals.

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  • 42.
    Stergiopoulou, Katerina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Jarvinen, Riku
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Kallio, Esa
    Persson, Moa
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Solar Orbiter Model-Data Comparison in Venus' Induced Magnetotail2023In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 128, no 2Article in journal (Refereed)
    Abstract [en]

    We investigate the structure of the Venusian magnetotail utilizing magnetic field and electron density measurements that cover a wide range of distances from the planet, from the first two Solar Orbiter Venus flybys. We examine the magnetic field components along the spacecraft trajectory up to 80 Venus radii down the tail. Even though the magnetic field behavior differs considerably between the two cases, we see extended electron density enhancements covering distances greater than ∼20 RV in both flybys. We compare the magnetic field measurements with a global hybrid model of the induced magnetosphere and magnetotail of Venus, to examine to what degree the observations can be understood with the simulation. The model upstream conditions are stationary and the solution encloses a large volume of 83 RV × 60 RV × 60 RV in which we look for spatial magnetic field and plasma variations. We rotate the simulation solution to describe different stationary upstream IMF clock angle cases with a 10° step and find the clock angle for which the agreement between observations and model is maximized along Solar Orbiter's trajectory in 1-min steps. We find that in both flybys there is better agreement with the observations when we rotate the model for some intervals, while there are parts that cannot be well reproduced by the model irrespective of how we vary the IMF clock angle, suggesting the presence of non-stationary features in  the Venus-solar wind interaction not accounted for in the hybrid model.

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  • 43.
    Takahashi, Kazue
    et al.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA..
    Turc, Lucile
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Kilpua, Emilia
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Takahashi, Naoko
    Univ Tokyo, Grad Sch Sci, Dept Earth & Planetary Sci, Tokyo, Japan..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Kajdic, Primoz
    Univ Nacl Autonoma Mexico, Inst Geofis, Ciudad Univ, Ciudad De Mexico, Mexico..
    Palmroth, Minna
    Univ Helsinki, Dept Phys, Helsinki, Finland.;Finnish Meteorol Inst, Helsinki, Finland..
    Pfau-Kempf, Yann
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Soucek, Jan
    Acad Sci Czech Republ, Inst Atmospher Phys, Prague, Czech Republic..
    Motoba, Tetsuo
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA..
    Hartinger, Michael D.
    Space Sci Inst, Boulder, CO USA.;Virginia Polytech Inst & State Univ, Blacksburg, VA 24061 USA..
    Artemyev, Anton
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Singer, Howard
    NOAA, Space Weather Predict Ctr, Boulder, CO USA..
    Ganse, Urs
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Battarbee, Markus
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Propagation of Ultralow-Frequency Waves from the Ion Foreshock into the Magnetosphere During the Passage of a Magnetic Cloud2021In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 126, no 2, article id e2020JA028474Article in journal (Refereed)
    Abstract [en]

    We have examined the properties of ultralow-frequency (ULF) waves in space (the ion foreshock, magnetosheath, and magnetosphere) and at dayside magnetometer stations (L = 1.6-6.5) during Earth's encounter with a magnetic cloud in the solar wind, which is characterized by magnetic fields with large magnitudes (similar to 14 nT) and small cone angles (similar to 30 degrees). In the foreshock, waves were excited at similar to 90 m Hz as expected from theory, but there were oscillations at other frequencies as well. Oscillations near 90 mHz were detected at the other locations in space, but they were not in general the most dominant oscillations. On the ground, pulsations in the approximate Pc2-Pc4 band (5 mHz-120 mHz) were continuously detected at all stations, with no outstanding spectral peaks near 90 mHz in the H component except at stations where the frequency of the third harmonic of standing Alfven waves had this frequency. The fundamental toroidal wave frequency was below 90 mHz at all stations. In the D component spectra, a minor spectral peak is found near 90 mHz at stations located at L < 3, and the power dropped abruptly above this frequency. Magnetospheric compressional wave power was much weaker on the nightside. A hybrid-Vlasov simulation indicates that foreshock ULF waves have short spatial scale lengths and waves transmitted into the magnetosphere are strongly attenuated away from noon.

  • 44.
    Trotta, Domenico
    et al.
    Imperial Coll London, Dept Phys, Blackett Lab, London SW7 2AZ, England..
    Horbury, Timothy S.
    Imperial Coll London, Dept Phys, Blackett Lab, London SW7 2AZ, England..
    Lario, David
    NASA Goddard Space Flight Ctr, Heliophys Sci Div, Greenbelt, MD 20771 USA..
    Vainio, Rami
    Univ Turku, Dept Phys & Astron, Turku, Finland..
    Dresing, Nina
    Univ Turku, Dept Phys & Astron, Turku, Finland..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Giacalone, Joe
    Univ Arizona, Lunar & Planetary Lab, Tucson, AZ USA..
    Hietala, Heli
    Queen Mary Univ London, Sch Phys & Astron, London E1 4NS, England..
    Wimmer-Schweingruber, Robert F.
    Univ Kiel, Inst Expt & Appl Phys, D-24118 Kiel, Germany..
    Berger, Lars
    Univ Kiel, Inst Expt & Appl Phys, D-24118 Kiel, Germany..
    Yang, Liu
    Univ Kiel, Inst Expt & Appl Phys, D-24118 Kiel, Germany..
    Irregular Proton Injection to High Energies at Interplanetary Shocks2023In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 957, no 2, article id L13Article in journal (Refereed)
    Abstract [en]

    How thermal particles are accelerated to suprathermal energies is an unsolved issue, crucial for many astrophysical systems. We report novel observations of irregular, dispersive enhancements of the suprathermal particle population upstream of a high-Mach-number interplanetary shock. We interpret the observed behavior as irregular "injections" of suprathermal particles resulting from shock front irregularities. Our findings, directly compared to self-consistent simulation results, provide important insights for the study of remote astrophysical systems where shock structuring is often neglected.

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  • 45.
    Turc, L.
    et al.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Roberts, O. W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Verscharen, D.
    Univ Coll London, Mullard Space Sci Lab, Dorking, Surrey, England..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Kajdic, P.
    Univ Nacl Autonoma Mexico, Dept Ciencias Espaciales, Inst Geofis, Mexico City, Mexico..
    Palmroth, M.
    Univ Helsinki, Dept Phys, Helsinki, Finland.;Finnish Meteorol Inst, Helsinki, Finland..
    Pfau-Kempf, Y.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Johlander, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Univ Helsinki, Dept Phys, Helsinki, Finland..
    Dubart, M.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Kilpua, E. K. J.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Soucek, J.
    Czech Acad Sci, Inst Atmospher Phys, Prague, Czech Republic..
    Takahashi, K.
    Johns Hopkins Univ Appl Phys Lab, Laurel, MD USA..
    Takahashi, N.
    Univ Tokyo, Grad Sch Sci, Dept Earth & Planetary Sci, Tokyo, Japan.;Radio Res Inst, Natl Inst Informat & Commun Technol, Tokyo, Japan..
    Battarbee, M.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Ganse, U.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Transmission of foreshock waves through Earth's bow shock2023In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, Vol. 19, no 1, p. 78-86Article in journal (Refereed)
    Abstract [en]

    The Earth's magnetosphere and its bow shock, which is formed by the interaction of the supersonic solar wind with the terrestrial magnetic field, constitute a rich natural laboratory enabling in situ investigations of universal plasma processes. Under suitable interplanetary magnetic field conditions, a foreshock with intense wave activity forms upstream of the bow shock. So-called 30 s waves, named after their typical period at Earth, are the dominant wave mode in the foreshock and play an important role in modulating the shape of the shock front and affect particle reflection at the shock. These waves are also observed inside the magnetosphere and down to the Earth's surface, but how they are transmitted through the bow shock remains unknown. By combining state-of-the-art global numerical simulations and spacecraft observations, we demonstrate that the interaction of foreshock waves with the shock generates earthward-propagating, fast-mode waves, which reach the magnetosphere. These findings give crucial insight into the interaction of waves with collisionless shocks in general and their impact on the downstream medium.

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  • 46.
    Turc, Lucile
    et al.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Taryus, Vertti
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Battarbee, Markus
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Ganse, Urs
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Johlander, Andreas
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Grandin, Maxime
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Pfau-Kempf, Yann
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Dubart, Maxime
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Palmroth, Minna
    Univ Helsinki, Dept Phys, Helsinki, Finland.;Finnish Meteorol Inst, Helsinki, Finland..
    Asymmetries in the Earth's dayside magnetosheath: results from global hybrid-Vlasov simulations2020In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 38, no 5, p. 1045-1062Article in journal (Refereed)
    Abstract [en]

    Bounded by the bow shock and the magnetopause, the magnetosheath forms the interface between solar wind and magnetospheric plasmas and regulates solar wind-magnetosphere coupling. Previous works have revealed pronounced dawn-dusk asymmetries in the magnetosheath properties. The dependence of these asymmetries on the upstream parameters remains however largely unknown. One of the main sources of these asymmetries is the bow shock configuration, which is typically quasi-parallel on the dawn side and quasi-perpendicular on the dusk side of the terrestrial magnetosheath because of the Parker spiral orientation of the interplanetary magnetic field (IMF) at Earth. Most of these previous studies rely on collections of spacecraft measurements associated with a wide range of upstream conditions which are processed in order to obtain average values of the magnetosheath parameters. In this work, we use a different approach and quantify the magnetosheath asymmetries in global hybrid-Vlasov simulations performed with the Vlasiator model. We concentrate on three parameters: the magnetic field strength, the plasma density, and the flow velocity. We find that the Vlasiator model reproduces the polarity of the asymmetries accurately but that their level tends to be higher than in spacecraft measurements, probably because the magnetosheath parameters are obtained from a single set of upstream conditions in the simulation, making the asymmetries more prominent. A set of three runs with different upstream conditions allows us to investigate for the first time how the asymmetries change when the angle between the IMF and the Sun-Earth line is reduced and when the Alfven Mach number decreases. We find that a more radial IMF results in a stronger magnetic field asymmetry and a larger variability of the magnetosheath density. In contrast, a lower Alfven Mach number leads to a reduced magnetic field asymmetry and a decrease in the variability of the magnetosheath density, the latter likely due to weaker foreshock processes. Our results highlight the strong impact of the quasi-parallel shock and its associated foreshock on global magnetosheath properties, in particular on the magnetosheath density, which is extremely sensitive to transient quasi-parallel shock processes, even with the perfectly steady upstream conditions in our simulations. This could explain the large variability of the density asymmetry levels obtained from spacecraft measurements in previous studies.

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  • 47.
    Vandegriff, Erik M.
    et al.
    Amer Univ, Washington, DC 20016 USA.;NASA Goddard Space Flight Ctr, Greenbelt, MD 20771 USA.;Univ Texas Arlington, Arlington, TX 76019 USA..
    Welling, Daniel T.
    Univ Michigan, Ann Arbor, MI USA..
    Mukhopadhyay, Agnit
    Univ Michigan, Ctr Space Environm Modeling, Ann Arbor, MI USA..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Morley, Steven K.
    Los Alamos Natl Lab, Los Alamos, NM USA..
    Lopez, Ramon E.
    Univ Texas Arlington, Arlington, TX 76019 USA..
    Exploring Localized Geomagnetic Disturbances in Global MHD: Physics and Numerics2024In: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 22, no 4, article id e2023SW003799Article in journal (Refereed)
    Abstract [en]

    One of the prominent effects of space weather is the formation of rapid geomagnetic field variations on Earth's surface driven by the magnetosphere-ionosphere system. These geomagnetic disturbances (GMDs) cause geomagnetically induced currents to run through ground conducting systems. In particular, localized GMDs (LGMDs) can be high amplitude and can have an effect on scale sizes less than 100 km, making them hazardous to power grids and difficult to predict. In this study, we examine the ability of the Space Weather Modeling Framework (SWMF) to reproduce LGMDs in the 7 September 2017 event using both existing and new metrics to quantify the success of the model against observation. We show that the high-resolution SWMF can reproduce LGMDs driven by ionospheric sources, but struggles to reproduce LGMDs driven by substorm effects. We calculate the global maxima of the magnetic fluctuations to show instances when the SWMF captures LGMDs at the correct times but not the correct locations. To remedy these shortcomings we suggest model developments that will directly impact the ability of the SWMF to reproduce LGMDs, most importantly updating the ionospheric conductance calculation from empirical to physics-based. Studying the negative effects of space weather on Earth is a crucial part of protecting ourselves and our technology from solar phenomena. Fluctuations in Earth's magnetic field cause high-amplitude currents to run through ground conducting systems such as underwater cables and power lines, causing damage to the hardware. Being able to predict these magnetic field fluctuations is essential to protecting ourselves and our technology; however these effects can be highly localized, making them more difficult to predict. This study presents an analysis of a high-resolution model run of Earth's magnetic field that captures localized magnetic fluctuations on the ground. We use the model results to explore the causes of these fluctuations in the model and compare the results with observation. We show that the model can reproduce magnetic fluctuations associated with some dynamics in Earth's ionosphere, but misses some of the fluctuations caused by complex dynamics farther out in Earth's magnetic field. We also show that in some cases the model captures fluctuations at the correct times but not the correct locations. Finally we suggest model improvements that will directly improve our model's ability to reproduce and predict localized magnetic fluctuations. High resolution Space Weather Modeling Framework can reproduce Localized Geomagnetic Disturbances (localized geomagnetic disturbances s (LGMDs)) driven by ionospheric sources Magnetospheric disturbances associated with substorms appear in model, but effects do not translate to LGMDs on the ground Improvements to calculation of ionospheric conductance and capture of substorm dynamics in model needed to better predict LGMDs

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  • 48.
    Werner, A. L. E.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Sorbonne Univ, CNRS, LATMOS IPSL, UVSQ, Paris, France.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Swedish Inst Space Phys, Uppsala, Sweden.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Swedish Inst Space Phys, Uppsala, Sweden.
    Temmer, M.
    Karl Franzens Univ Graz, Inst Phys, Graz, Austria.
    Modeling the Multiple CME Interaction Event on 6-9 September 2017 with WSA-ENLIL plus Cone2019In: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 17, no 2, p. 357-369Article in journal (Refereed)
    Abstract [en]

    A series of coronal mass ejections (CMEs) erupted from the same active region between 4-6 September 2017. Later, on 6-9 September, two interplanetary (IP) shocks reached LE creating a complex and geoeffective plasma structure. To understand the processes leading up to the formation of the two shocks, we model the CMEs with the Wang-Sheeley-Arge (WSA)-ENLIL+Cone model. The first two CMEs merged already in the solar corona driving the first IP shock. In IP space, another fast CME presumably interacted with the flank of the preceding CMEs and caused the second shock detected in situ. By introducing a customized density enhancement factor (dcld) in the WSA-ENLIL+Cone model based on coronagraph image observations, the predicted arrival time of the first IP shock was drastically improved. When the dcld factor was tested on a well-defined single CME event from 12 July 2012 the shock arrival time saw similar improvement. These results suggest that the proposed approach may be an alternative to improve the forecast for fast and simple CMEs. Further, the slowly decelerating kilometric type II radio burst confirms that the properties of the background solar wind have been preconditioned by the passage of the first IP shock. This likely caused the last CME to experience insignificant deceleration and led to the early arrival of the second IP shock. This result emphasizes the need to take preconditioning of the IP medium into account when making forecasts of CMEs erupting in quick succession.

  • 49.
    Yordanova, Emiliya
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Temmer, M.
    Graz Univ, Inst Phys, Graz, Austria..
    Dumbovic, M.
    Univ Zagreb, Fac Geodesy, Hvar Observ, Zagreb, Croatia..
    Scolini, C.
    Royal Observ Belgium, Brussels, Belgium..
    Paouris, E.
    George Mason Univ, Dept Phys & Astron, Fairfax, VA USA.;Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Werner, A. L. Elisabeth
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Sorriso-Valvo, Luca
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. CNR, Inst Plasma Sci & Technol ISTP, Bari, Italy; KTH Royal Inst Technol, Sch Elect Engn & Comp Sci, Space & Plasma Phys, Stockholm, Sweden.
    Refined Modeling of Geoeffective Fast Halo CMEs During Solar Cycle 242024In: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 22, no 1, article id e2023SW003497Article in journal (Refereed)
    Abstract [en]

    The propagation of geoeffective fast halo coronal mass ejections (CMEs) from solar cycle 24 has been investigated using the European Heliospheric Forecasting Information Asset (EUHFORIA), ENLIL, Drag-Based Model (DBM) and Effective Acceleration Model (EAM) models. For an objective comparison, a unified set of a small sample of CME events with similar characteristics has been selected. The same CME kinematic parameters have been used as input in the propagation models to compare their predicted arrival times and the speed of the interplanetary (IP) shocks associated with the CMEs. The performance assessment has been based on the application of an identical set of metrics. First, the modeling of the events has been done with default input concerning the background solar wind, as would be used in operations. The obtained CME arrival forecast deviates from the observations at L1, with a general underestimation of the arrival time and overestimation of the impact speed (mean absolute error [MAE]: 9.8 ± 1.8–14.6 ± 2.3 hr and 178 ± 22–376 ± 54 km/s). To address this discrepancy, we refine the models by simple changes of the density ratio (dcld) between the CME and IP space in the numerical, and the IP drag (γ) in the analytical models. This approach resulted in a reduced MAE in the forecast for the arrival time of 8.6 ± 2.2–13.5 ± 2.2 hr and the impact speed of 51 ± 6–243 ± 45 km/s. In addition, we performed multi-CME runs to simulate potential interactions. This leads, to even larger uncertainties in the forecast. Based on this study we suggest simple adjustments in the operational settings for improving the forecast of fast halo CMEs.

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  • 50.
    Yordanova, Emiliya
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Voros, Zoltan
    Austrian Acad Sci, Space Res Inst, Graz, Austria.;Eotvos Lorand Res Network, Inst Earth Phys & Space Sci, Sopron, Hungary..
    Sorriso-Valvo, L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. CNR, Ist Sci & Tecnol Plasmi, Bari, Italy..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Kilpua, Emilia
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    A Possible Link between Turbulence and Plasma Heating2021In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 921, no 1, article id 65Article in journal (Refereed)
    Abstract [en]

    Numerical simulations and experimental results have shown that the formation of current sheets in space plasmas can be associated with enhanced vorticity. Also, in simulations the generation of such structures is associated with strong plasma heating. Here, we compare four-point measurements in the terrestrial magnetosheath turbulence from the Magnetospheric Multiscale mission of the flow vorticity and the magnetic field curlometer versus their corresponding one-point proxies PVI(V) and PVI(B) based on the Partial Variance of Increments (PVI) method. We show that the one-point proxies are sufficiently precise in identifying not only the generic features of the current sheets and vortices statistically, but also their appearance in groups associated with plasma heating. The method has been further applied to the region of the turbulent sheath of an interplanetary coronal mass ejection (ICME) observed at L1 by the WIND spacecraft. We observe current sheets and vorticity associated heating in larger groups (blobs), which so far have not been considered in the literature on turbulent data analysis. The blobs represent extended spatial regions of activity with enhanced regional correlations between the occurrence of conditioned currents and vorticity, which at the same time are also correlated with enhanced temperatures. This heating mechanism is substantially different from the plasma heating in the vicinity of the ICME shock, where plasma beta is strongly fluctuating and there is no vorticity. The proposed method describes a new pathway for linking the plasma heating and plasma turbulence, and it is relevant to in situ observations when only single spacecraft measurements are available.

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