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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.
    Alberti, Tommaso
    et al.
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy.
    Consolini, Giuseppe
    INAF Ist Astrofis & Planetol Spaziali, , Rome, Italy.
    Carbone, Vincenzo
    Univ Calabria, Dipartimento Fis, Arcavacata Di Rende, Italy.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Marcucci, Maria Federica
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy.
    De Michelis, Paola
    Ist Nazl Geofis & Vulcanol, Rome, Italy.
    Multifractal and Chaotic Properties of Solar Wind at MHD and Kinetic Domains: An Empirical Mode Decomposition Approach2019In: Entropy, E-ISSN 1099-4300, Vol. 21, no 3, article id 320Article in journal (Refereed)
    Abstract [en]

    Turbulence, intermittency, and self-organized structures in space plasmas can be investigated by using a multifractal formalism mostly based on the canonical structure function analysis with fixed constraints about stationarity, linearity, and scales. Here, the Empirical Mode Decomposition (EMD) method is firstly used to investigate timescale fluctuations of the solar wind magnetic field components; then, by exploiting the local properties of fluctuations, the structure function analysis is used to gain insights into the scaling properties of both inertial and kinetic/dissipative ranges. Results show that while the inertial range dynamics can be described in a multifractal framework, characterizing an unstable fixed point of the system, the kinetic/dissipative range dynamics is well described by using a monofractal approach, because it is a stable fixed point of the system, unless it has a higher degree of complexity and chaos.

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  • 3.
    Benella, Simone
    et al.
    Ist Nazl Astrofis, Ist Astrofis & Planetol Spaziali, Via Fosso Cavaliere 100, I-00133 Rome, Italy..
    Stumpo, Mirko
    Ist Nazl Astrofis, Ist Astrofis & Planetol Spaziali, Via Fosso Cavaliere 100, I-00133 Rome, Italy..
    Alberti, Tommaso
    Ist Nazl Geofis & Vulcanol, Via Vigna Murata, I-00143 Rome, Italy..
    Pezzi, Oreste
    Ist Nazl Astrofis, Ist Astrofis & Planetol Spaziali, Via Fosso Cavaliere 100, I-00133 Rome, Italy.;CNR, Ist Sci & Tecnol Plasmi, Via Amendola 122 D, I-70126 Bari, Italy..
    Papini, Emanuele
    Ist Nazl Astrofis, Ist Astrofis & Planetol Spaziali, Via Fosso Cavaliere 100, I-00133 Rome, Italy..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Valentini, Francesco
    Univ Calabria, Dipartimento Fis, Ponte P Bucci,Cubo 31C, I-87036 Arcavacata Di Rende, CS, Italy..
    Consolini, Giuseppe
    Ist Nazl Astrofis, Ist Astrofis & Planetol Spaziali, Via Fosso Cavaliere 100, I-00133 Rome, Italy..
    Linking the Langevin equation to scaling properties of space plasma turbulence at sub-ion scales2023In: Physical Review Research, E-ISSN 2643-1564, Vol. 5, no 4, article id L042014Article in journal (Refereed)
    Abstract [en]

    Current understanding of the kinetic-scale turbulence in weakly collisional plasmas still remains elusive. We employ a general framework in which the turbulent energy transfer is envisioned as a scale-to-scale Langevin process. Fluctuations in the sub-ion range show a global scale invariance, thus suggesting a homogeneous energy repartition. In this Letter, we interpret such a feature by linking the drift term of the Langevin equation to scaling properties of fluctuations. Theoretical expectations are verified on solar wind observations and numerical simulations, thus giving relevance to the proposed framework for understanding kinetic-scale turbulence in space plasmas.

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  • 4.
    Benella, Simone
    et al.
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy..
    Stumpo, Mirko
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy.;Univ Roma Tor Vergata, Dipartimento Fis, Rome, Italy..
    Consolini, Giuseppe
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy..
    Alberti, Tommaso
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy..
    Laurenza, Monica
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Kramers-Moyal analysis of interplanetary magnetic field fluctuations at sub-ion scales2022In: Rendiconti Lincei SCIENZE FISICHE E NATURALI, ISSN 2037-4631, E-ISSN 1720-0776, Vol. 33, no 4, p. 721-728Article in journal (Refereed)
    Abstract [en]

    In the framework of statistical time series analysis of complex dynamics, we present a multiscale characterization of solar wind turbulence in the near-earth environment. The data analysis, based on the Markov process theory, is meant to estimate the Kramers-Moyal coefficients associated with the measured magnetic field fluctuations. In fact, when the scale-to-scale dynamics can be successfully described as a Markov process, first- and second-order Kramers-Moyal coefficients provide a complete description of the dynamics in terms of Langevin stochastic process. The analysis is carried out using high-resolution magnetic field measurements gathered by Cluster during a fast solar wind period on January 20, 2007. This analysis extends recent findings in the near-Sun environment with the aim of testing the universality of the Markovian nature of the magnetic field fluctuations in the sub-ion/kinetic domain.

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  • 5.
    Breuillard, H.
    et al.
    Univ Paris Sud, Sorbonne Univ, Ecole Polytech, Lab Phys Plasmas,UMR7648,CNRS, Paris, France.
    Matteini, L.
    UPMC Univ Paris 06, Univ Paris Diderot, PSL Res Univ, LESIA Observ Paris,CNRS, Meudon, France.
    Argall, M. R.
    Univ New Hampshire, Durham, NH 03824 USA.
    Sahraoui, F.
    Univ Paris Sud, Sorbonne Univ, Ecole Polytech, Lab Phys Plasmas,UMR7648,CNRS, Paris, France.
    Andriopoulou, M.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Le Contel, O.
    Univ Paris Sud, Sorbonne Univ, Ecole Polytech, Lab Phys Plasmas,UMR7648,CNRS, Paris, France.
    Retino, A.
    Univ Paris Sud, Sorbonne Univ, Ecole Polytech, Lab Phys Plasmas,UMR7648,CNRS, Paris, France.
    Mirioni, L.
    Univ Paris Sud, Sorbonne Univ, Ecole Polytech, Lab Phys Plasmas,UMR7648,CNRS, Paris, France.
    Huang, S. Y.
    Wuhan Univ, Sch Elect & Informat, Beijing, Peoples R China.
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.
    Wilder, F. D.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.
    Goodrich, K. A.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.
    Ahmadi, N.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Turner, D. L.
    Aerosp Corp, Space Sci Dept, El Segundo, CA 90245 USA.
    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.
    Lindqvist, P. -A
    Chasapis, A.
    Univ Delaware, Newark, DE USA.
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA.
    Torbert, R. B.
    Univ New Hampshire, Durham, NH 03824 USA.
    Russell, C. T.
    Univ Calif Los Angeles, Los Angeles, CA USA.
    Magnes, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Strangeway, R. J.
    Plaschke, F.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Moore, T. E.
    Giles, B. L.
    Paterson, W. R.
    Pollock, C. J.
    Lavraud, B.
    Univ Paul Sabatier, CNRS UMR5277, IRAP, Toulouse, France.
    Fuselier, S. A.
    Southwest Res Inst, San Antonio, TX USA.
    Cohen, I. J.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA.
    New Insights into the Nature of Turbulence in the Earth's Magnetosheath Using Magnetospheric MultiScale Mission Data2018In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 859, no 2, article id 127Article in journal (Refereed)
    Abstract [en]

    The Earth's magnetosheath, which is characterized by highly turbulent fluctuations, is usually divided into two regions of different properties as a function of the angle between the interplanetary magnetic field and the shock normal. In this study, we make use of high-time resolution instruments on board the Magnetospheric MultiScale spacecraft to determine and compare the properties of subsolar magnetosheath turbulence in both regions, i. e., downstream of the quasi-parallel and quasi-perpendicular bow shocks. In particular, we take advantage of the unprecedented temporal resolution of the Fast Plasma Investigation instrument to show the density fluctuations down to sub-ion scales for the first time. We show that the nature of turbulence is highly compressible down to electron scales, particularly in the quasi-parallel magnetosheath. In this region, the magnetic turbulence also shows an inertial (Kolmogorov-like) range, indicating that the fluctuations are not formed locally, in contrast with the quasi-perpendicular magnetosheath. We also show that the electromagnetic turbulence is dominated by electric fluctuations at sub-ion scales (f > 1Hz) and that magnetic and electric spectra steepen at the largest-electron scale. The latter indicates a change in the nature of turbulence at electron scales. Finally, we show that the electric fluctuations around the electron gyrofrequency are mostly parallel in the quasi-perpendicular magnetosheath, where intense whistlers are observed. This result suggests that energy dissipation, plasma heating, and acceleration might be driven by intense electrostatic parallel structures/waves, which can be linked to whistler waves.

  • 6.
    Breuillard, H.
    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.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Alexandrova, O.
    LESIA Observ Paris Meudon, Meudon, France..
    The Effects Of Kinetic Instabilities On Small-Scale Turbulence In Earth's Magnetosheath2016In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 829, no 1, article id 54Article in journal (Refereed)
    Abstract [en]

    The Earth's magnetosheath is the region delimited by the bow shock and the magnetopause. It is characterized by highly turbulent fluctuations covering all scales from MHD down to kinetic scales. Turbulence is thought to play a fundamental role in key processes such as energy transport and dissipation in plasma. In addition to turbulence, different plasma instabilities are generated in the magnetosheath because of the large anisotropies in plasma temperature introduced by its boundaries. In this study we use high-quality magnetic field measurements from Cluster spacecraft to investigate the effects of such instabilities on the small-scale turbulence (from ion down to electron scales). We show that the steepening of the power spectrum of magnetic field fluctuations in the magnetosheath occurs at the largest characteristic ion scale. However, the spectrum can be modified by the presence of waves/structures at ion scales, shifting the onset of the small-scale turbulent cascade toward the smallest ion scale. This cascade is therefore highly dependent on the presence of kinetic instabilities, waves, and local plasma parameters. Here we show that in the absence of strong waves the small-scale turbulence is quasi-isotropic and has a spectral index alpha approximate to 2.8. When transverse or compressive waves are present, we observe an anisotropy in the magnetic field components and a decrease in the absolute value of alpha. Slab/2D turbulence also develops in the presence of transverse/compressive waves, resulting in gyrotropy/non-gyrotropy of small-scale fluctuations. The presence of both types of waves reduces the anisotropy in the amplitude of fluctuations in the small-scale range.

  • 7.
    Carbone, F.
    et al.
    Univ Calabria, Natl Res Council, Inst Atmospher Pollut Res, I-87036 Arcavacata Di Rende, Italy..
    Sorriso-Valvo, Luca
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Ist Sci & Tecnol Plasmi, CNR, Via Amendola 122-D, I-70126 Bari, Italy.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Steinvall, Konrad
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vecchio, A.
    Univ Paris Diderot, Sorbonne Univ, Univ PSL, Observ Paris, Sorbonne Paris Cite,5 Pl Jules Janssen, F-92195 Meudon, France.;Radboud Univ Nijmegen, Res Inst Math Astrophys & Particle Phys, Nijmegen, Netherlands..
    Telloni, D.
    Natl Inst Astrophys, Astrophys Observ Torino, Turin, Italy..
    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.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, Erik P. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vásconez, C. L.
    Escuela Politec Nacl, Dept Fis, Ladron de Guevara E11-253, Quito 170525, Ecuador..
    Maksimovic, M.
    Radboud Univ Nijmegen, Res Inst Math Astrophys & Particle Phys, Nijmegen, Netherlands..
    Bruno, R.
    Natl Inst Astrophys INAF, Inst Space Astrophys & Planetol IAPS, Via Fosso del Cavaliere 100, I-00133 Rome, Italy..
    D'Amicis, R.
    Natl Inst Astrophys INAF, Inst Space Astrophys & Planetol IAPS, Via Fosso del Cavaliere 100, I-00133 Rome, Italy..
    Bale, S. D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.;Univ Calif Berkeley, Phys Dept, Berkeley, CA 94720 USA..
    Chust, T.
    Univ Paris Saclay, Observ Paris, Sorbonne Univ, Ecole Polytech,LPP,CNRS, Paris, France..
    Krasnoselskikh, V.
    CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France..
    Kretzschmar, M.
    CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France.;Univ Orleans, Orleans, France..
    Lorfèvre, E.
    CNES, 18 Ave Edouard Belin, F-31400 Toulouse, France..
    Plettemeier, D.
    Tech Univ Dresden, Wurzburger Str 35, D-01187 Dresden, Germany..
    Soucek, J.
    Czech Acad Sci, Inst Atmospher Phys, Prague, Czech Republic..
    Steller, M.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Stverák, S.
    Czech Acad Sci, Inst Atmospher Phys, Prague, Czech Republic.;Czech Acad Sci, Astron Inst, Prague, Czech Republic..
    Trávnicek, P.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.;Czech Acad Sci, Inst Atmospher Phys, Prague, Czech Republic..
    Vaivads, A.
    CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France.;Royal Inst Technol, Sch Elect Engn & Comp Sci, Dept Space & Plasma Phys, Stockholm, Sweden..
    Horbury, T. S.
    Imperial Coll London, Blackett Lab, Space & Atmospher Phys, London SW7 2AZ, England..
    O'Brien, H.
    Imperial Coll London, Blackett Lab, Space & Atmospher Phys, London SW7 2AZ, England..
    Angelini, V.
    Imperial Coll London, Blackett Lab, Space & Atmospher Phys, London SW7 2AZ, England..
    Evans, V.
    Imperial Coll London, Blackett Lab, Space & Atmospher Phys, London SW7 2AZ, England..
    Statistical study of electron density turbulence and ion-cyclotron waves in the inner heliosphere: Solar Orbiter observations2021In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 656, article id A16Article in journal (Refereed)
    Abstract [en]

    Context. The recently released spacecraft potential measured by the RPW instrument on board Solar Orbiter has been used to estimate the solar wind electron density in the inner heliosphere.

    Aims. The measurement of the solar wind’s electron density, taken in June 2020, has been analysed to obtain a thorough characterization of the turbulence and intermittency properties of the fluctuations. Magnetic field data have been used to describe the presence of ion-scale waves.

    Methods. To study and quantify the properties of turbulence, we extracted selected intervals. We used empirical mode decomposition to obtain the generalized marginal Hilbert spectrum, equivalent to the structure functions analysis, which additionally reduced issues typical of non-stationary, short time series. The presence of waves was quantitatively determined by introducing a parameter describing the time-dependent, frequency-filtered wave power.

    Results. A well-defined inertial range with power-law scalng was found almost everywhere in the sample studied. However, the Kolmogorov scaling and the typical intermittency effects are only present in fraction of the samples. Other intervals have shallower spectra and more irregular intermittency, which are not described by models of turbulence. These are observed predominantly during intervals of enhanced ion frequency wave activity. Comparisons with compressible magnetic field intermittency (from the MAG instrument) and with an estimate of the solar wind velocity (using electric and magnetic field) are also provided to give general context and help determine the cause of these anomalous fluctuations.

  • 8.
    Carbone, Francesco
    et al.
    Univ Calabria, Natl Res Council, Inst Atmospher Pollut Res, I-87036 Arcavacata Di Rende, Italy.
    Telloni, Daniele
    Natl Inst Astrophys Astrophys Observ Torino, Via Osservatorio 20, I-10025 Pino Torinese, Italy.
    Yordanova, Emiliya
    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, Ist Sci & Tecnol Plasmi, Via Amendola 112-D, I-70126 Bari, Italy.
    Modulation of Solar Wind Impact on the Earth's Magnetosphere during the Solar Cycle2022In: Universe, E-ISSN 2218-1997, Vol. 8, no 6, article id 330Article in journal (Refereed)
    Abstract [en]

    The understanding of extreme geomagnetic storms is one of the key issues in space weather. Such phenomena have been receiving increasing attention, especially with the aim of forecasting strong geomagnetic storms generated by high-energy solar events since they can severely perturb the near-Earth space environment. Here, the disturbance storm time index Dst, a crucial geomagnetic activity proxy for Sun-Earth interactions, is analyzed as a function of the energy carried by different solar wind streams. To determine the solar cycle activity influence on Dst, a 12-year dataset was split into sub-periods of maximum and minimum solar activity. Solar wind energy and geomagnetic activity were closely correlated for both periods of activity. Slow wind streams had negligible effects on Earth regardless of their energy, while high-speed streams may induce severe geomagnetic storming depending on the energy (kinetic or magnetic) carried by the flow. The difference between the two periods may be related to the higher rate of geo-effective events during the maximum activity, where coronal mass ejections represent the most energetic and geo-effective driver. During the minimum period, despite a lower rate of high energetic events, a moderate disturbance in the Dst index can be induced.

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  • 9.
    Chiappetta, Federica
    et al.
    Univ Calabria, Dipartimento Fis, Ponte P Bucci Cubo 31C, Arcavacata Di Rende, CS, Italy..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Voros, Zoltan
    Space Res Inst, Schmiedlstr 6, Graz, Austria.;HUN REN, Inst Earth Phys & Space Sci, Sopron, Hungary..
    Lepreti, Fabio
    Univ Calabria, Dipartimento Fis, Ponte P Bucci Cubo 31C, Arcavacata Di Rende, CS, Italy.;Ist Nazl Astrofis INAF, Direz Sci, Rome, Italy..
    Carbone, Vincenzo
    Univ Calabria, Dipartimento Fis, Ponte P Bucci Cubo 31C, Arcavacata Di Rende, CS, Italy.;Ist Nazl Astrofis INAF, Direz Sci, Rome, Italy..
    Energy Conversion through a Fluctuation-Dissipation Relation at Kinetic Scales in the Earth's Magnetosheath2023In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 957, no 2, article id 98Article in journal (Refereed)
    Abstract [en]

    Low-frequency fluctuations in the interplanetary medium represent a turbulent environment where universal scaling behavior, generated by an energy cascade, has been investigated. On the contrary, in some regions, for example, the magnetosheath, universality of statistics of fluctuations is lost. However, at kinetic scales where energy must be dissipated, the energy conversion seems to be realized through a mechanism similar to the free solar wind. Here we propose a Langevin model for magnetic fluctuations at kinetic scales, showing that the resulting fluctuation-dissipation relation is capable of describing the gross features of the spectral observations at kinetic scales in the magnetosheath. The fluctuation-dissipation relation regulates the energy conversion by imposing a relationship between fluctuations and dissipation, which at high frequencies are active at the same time in the same range of scales and represent two ingredients of the same physical process.

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  • 10.
    Consolini, G.
    et al.
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy..
    Alberti, T.
    Univ Calabria, Dept Phys, Arcavacata Di Rende, Italy..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Marcucci, M. F.
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy..
    Echim, M.
    Royal Belgian Inst Space Aeron, Brussels, Belgium.;Inst Space Sci, Magurele, Romania..
    A Hilbert-Huang transform approach to space plasma turbulence at kinetic scales2017In: 16TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE: TURBULENCE, STRUCTURES, AND PARTICLE ACCELERATION THROUGHOUT THE HELIOSPHERE AND BEYOND / [ed] Zank, G P, IOP PUBLISHING LTD , 2017, article id UNSP 012003Conference paper (Refereed)
    Abstract [en]

    Heliospheric space plasmas are highly turbulent media and display multiscale fluctuations over a wide range of scales from the magnetohydrodynamic domain down to the kinetic one. The study of turbulence features is traditionally based on spectral and canonical structure function analysis. Here, we present an novel approach to the analysis of the multiscale nature of plasma turbulent fluctuations by means of Hilbert-Huang Transform (HHT). In particular we present a preliminary application of this technique to magnetic field fluctuations at kinetic scales in a fast solar wind stream as observed by Cluster mission. The HHT-energy spectrum reveals the intermittent and multiscale nature of fluctuation frequency at kinetic scales indicating that there are no-persistent and long standing frequencies.

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  • 11.
    Consolini, G.
    et al.
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy.
    Giannattasio, F.
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Voeroes, Z.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Marcucci, M. F.
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy.
    Echim, M.
    Belgian Inst Aeron, Brussels, Belgium;Inst Space Sci, Magurele, Romania.
    Chang, T.
    MIT, Kavli Inst Astrophys & Space Res, 77 Massachusetts Ave, Cambridge, MA 02139 USA.
    On the scaling features of magnetic field fluctuations at non-MHD scales in turbulent space plasmas2016In: 15th Annual International Astrophysics Conference: "The Science Of Ed Stone: Celebrating His 80Th Birthday" / [ed] Zank, G P, 2016, article id 012003Conference paper (Refereed)
    Abstract [en]

    In several different contexts space plasmas display intermittent turbulence at magneto-hydro-dynamic (MHD) scales, which manifests in anomalous scaling features of the structure functions of the magnetic field increments. Moving to smaller scales, i.e. below the ion-cyclotron and/or ion inertial length, these scaling features are still observed, even though its is not clear if these scaling features are still anomalous or not. Here, we investigate the nature of scaling properties of magnetic field increments at non-MHD scales for a period of fast solar wind to investigate the occurrence or not of multifractal features and collapsing of probability distribution functions (PDFs) using the novel Rank-Ordered Multifractal Analysis (ROMA) method, which is more sensitive than the traditional structure function approach. We find a strong evidence for the occurrence of a near mono-scaling behavior, which suggests that the observed turbulent regime at non-MHD scales mainly displays a mono-fractal nature of magnetic field increments. The results are discussed in terms of a non-compact fractal structure of the dissipation field.

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  • 12. Consolini, G.
    et al.
    Grandioso, S.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Marcucci, M. F.
    Pallocchia, G.
    Statistical and Scaling Features of Fluctuations in the Dissipation Range During a Reconnection Event2015In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 804, no 1, article id 19Article in journal (Refereed)
    Abstract [en]

    Reconnection events in space plasmas are accompanied by the occurrence of large-amplitude turbulent fluctuations of the magnetic and electric field, covering a wide range of temporal and spatial scales. Here, we study the scaling and statistical features of magnetic and electric field fluctuations below the ion-gyroperiod (i.e., in the dissipation domain) by carefully investigating the occurrence of local or global scaling features during a reconnection event studied by Eastwood et al. Our results point toward the presence of a global scale invariance, i.e., a mono-fractal nature, of fluctuations above the ion-cyclotron frequency and at spatial scales near the ion-inertial length.

  • 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.
    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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  • 16.
    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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  • 17.
    Dwivedi, N. K.
    et al.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria.
    Kumar, S.
    Kyung Hee Univ, Sch Space Res, Yongin 446701, Gyeonggi Do, South Korea;Shandong Univ, Inst Space Sci, Shandong Prov Key Lab Opt Astron & Solar Terr Env, Weihai, Peoples R China.
    Kovacs, P.
    Min & Geol Survey Hungary, Budapest, Hungary.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Echim, M.
    Inst Royale Aeron Spatiale Belgique, B-1180 Brussels, Belgium.
    Sharma, R. P.
    Indian Inst Technol Delhi, Ctr Energy Studies, Delhi, India.
    Khodachenko, M. L.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria;Moscow MV Lomonosov State Univ, Skobeltsyn Inst Nucl Phys, Moscow, Russia;Russian Acad Sci, Inst Astron, Moscow 119017, Russia.
    Sasunov, Y.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria;Moscow MV Lomonosov State Univ, Skobeltsyn Inst Nucl Phys, Moscow, Russia.
    Implication of kinetic Alfvén waves to magnetic field turbulence spectra: Earth's magnetosheath2019In: Astrophysics and Space Science, ISSN 0004-640X, E-ISSN 1572-946X, Vol. 364, no 6, article id 101Article in journal (Refereed)
    Abstract [en]

    In the present paper, we investigate the power-law behaviour of the magnetic field spectra in the Earth's magnetosheath region using Cluster spacecraft data under solar minimum condition. The power spectral density of the magnetic field data and spectral slopes at various frequencies are analysed. Propagation angle, kB, and compressibility, R vertical bar, are used to test the nature of turbulent fluctuations. The magnetic field spectra have the spectral slopes, , between -1.5 to 0 down to spatial scales of 20i (where i is ion gyroradius), and show clear evidence of a transition to steeper spectra for small scales with a second power-law, having between -2.6 to -1.8. At low frequencies, fsc<0.3fci (where fci is ion gyro-frequency), kB approximate to 90 degrees to the mean magnetic field, B0, and R vertical bar shows a broad distribution, 0.1R vertical bar 0.9. On the other hand at fsc>10fci, kB exhibits a broad range, 30 degrees kB90 degrees, while R vertical bar has a small variation: 0.2R vertical bar 0.5. We conjecture that at high frequencies, the perpendicularly propagating Alfven waves could partly explain the statistical analysis of spectra. To support our prediction of kinetic Alfven wave dominated spectral slope behaviour at high frequency, we also present a theoretical model and simulate the magnetic field turbulence spectra due to nonlinear evolution of kinetic Alfven waves. The present study also shows the analogy between the observational and simulated spectra.

  • 18.
    Eriksson, Elin
    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.
    Vaivads, Andris
    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.
    Divin, Andrey
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Physics Department, St. Petersburg State University, St. Petersburg, Russia.
    Khotyaintsev, Yuri V.
    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.
    André, Mats
    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.
    Electron Energization at a Reconnecting Magnetosheath Current Sheet2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 16Article in journal (Refereed)
    Abstract [en]

    We present observations of electron energization within a sub-ion-scale magnetosheath current sheet (CS). A number of signatures indicate ongoing reconnection, including the thickness of the CS (∼0.7 ion inertial length), nonzero normal magnetic field, Hall magnetic fields with electrons carrying the Hall currents, and electron heating. We observe localized electron acceleration and heating parallel to the magnetic field at the edges of the CS. Electrostatic waves observed in these regions have low phase velocity and small wave potentials and thus cannot provide the observed acceleration and heating. Instead, we find that the electrons are accelerated by a parallel potential within the separatrix regions. Similar acceleration has been reported based on magnetopause and magnetotail observations.Thus, despite the different plasma conditions in magnetosheath, magnetopause, and magnetotail,the acceleration mechanism and corresponding heating of electrons is similar.

  • 19.
    Eriksson, Elin
    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, Space Plasma Physics.
    Vaivads, Andris
    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
    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.
    Hietala, H.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA USA..
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Avanov, L. A.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Dorelli, J. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.;Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Lavraud, B.
    CNRS, IRAP, Toulouse, France..
    Paterson, W. R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Pollock, C. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Saito, Y.
    JAXA, Chofu, Tokyo, Japan..
    Magnes, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Russell, C.
    Torbert, R.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Ergun, R.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA..
    Lindqvist, P-A
    Burch, J.
    Southwest Res Inst, San Antonio, TX USA..
    Strong current sheet at a magnetosheath jet: Kinetic structure and electron acceleration2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 10, p. 9608-9618Article in journal (Refereed)
    Abstract [en]

    Localized kinetic-scale regions of strong current are believed to play an important role in plasma thermalization and particle acceleration in turbulent plasmas. We present a detailed study of a strong localized current, 4900 nA m(-2), located at a fast plasma jet observed in the magnetosheath downstream of a quasi-parallel shock. The thickness of the current region is similar to 3 ion inertial lengths and forms at a boundary separating magnetosheath-like and solar wind-like plasmas. On ion scales the current region has the shape of a sheet with a significant average normal magnetic field component but shows strong variations on smaller scales. The dynamic pressure within the magnetosheath jet is over 3 times the solar wind dynamic pressure. We suggest that the current sheet is forming due to high velocity shears associated with the jet. Inside the current sheet we observe local electron acceleration, producing electron beams, along the magnetic field. However, there is no clear sign of ongoing reconnection. At higher energies, above the beam energy, we observe a loss cone consistent with part of the hot magnetosheath-like electrons escaping into the colder solar wind-like plasma. This suggests that the acceleration process within the current sheet is similar to the one that occurs at shocks, where electron beams and loss cones are also observed. Therefore, electron beams observed in the magnetosheath do not have to originate from the bow shock but can also be generated locally inside the magnetosheath.

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  • 20.
    Greco, A.
    et al.
    Univ Calabria, Dipartimento Fis, I-87036 Arcavacata Di Rende, CS, Italy..
    Perri, S.
    Univ Calabria, Dipartimento Fis, I-87036 Arcavacata Di Rende, CS, Italy..
    Servidio, S.
    Univ Calabria, Dipartimento Fis, I-87036 Arcavacata Di Rende, CS, Italy..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Veltri, P.
    Univ Calabria, Dipartimento Fis, I-87036 Arcavacata Di Rende, CS, Italy..
    The Complex Structure Of Magnetic Field Discontinuities In The Turbulent Solar Wind2016In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 823, no 2, article id L39Article in journal (Refereed)
    Abstract [en]

    Using high-resolution Cluster satellite observations and a multi-dimensional intermittency technique, we show that the magnetic discontinuities in the turbulent solar wind are connected through the spatial scales, going from proton down to electron scales. In some circumstances, their structure resembles the Harris equilibrium profile in plasmas. Observations are consistent with a scenario where many current layers develop in turbulence and where the outflow of these reconnection events are characterized by complex sub-proton networks of secondary islands, in a self-similar way. Although in the past these pictures have been speculated to be separately ubiquitous, through theories and simulations, the present work confirms that "reconnection in turbulence" and "turbulent reconnection" coexist in space plasmas.

  • 21.
    Gurchumelia, Alexandre
    et al.
    Ivane Javakhishvili Tbilisi State Univ, Dept Phys, Tbilisi, Georgia.;E Kharadze Georgian Natl Astrophys Observ, Tbilisi, Georgia..
    Sorriso-Valvo, Luca
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. CNR Inst Sci & Technol Plasmas, Bari, Italy..
    Burgess, David
    Queen Mary Univ London, Dept Phys & Astron, London, England..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Elbakidze, Khatuna
    Ivane Javakhishvili Tbilisi State Univ, I Vekua Inst Appl Math, Tbilisi, Georgia.;Int Black Sea Univ, Fac Business & Technol, Tbilisi, Georgia.;Ivane Javakhishvili Tbilisi State Univ, M Nodia Inst Geophys, Tbilisi, Georgia..
    Kharshiladze, Oleg
    Ivane Javakhishvili Tbilisi State Univ, Dept Phys, Tbilisi, Georgia..
    Kvaratskhelia, Diana
    Int Black Sea Univ, Fac Business & Technol, Tbilisi, Georgia.;Ivane Javakhishvili Tbilisi State Univ, M Nodia Inst Geophys, Tbilisi, Georgia.;Sokhumi State Univ, Fac Nat Sci Math Technol & Pharm, Tbilisi, Georgia..
    Comparing Quasi-Parallel and Quasi-Perpendicular Configuration in the Terrestrial Magnetosheath: Multifractal Analysis2022In: Frontiers in Physics, E-ISSN 2296-424X, Vol. 10, article id 903632Article in journal (Refereed)
    Abstract [en]

    The terrestrial magnetosheath is characterized by large-amplitude magnetic field fluctuations. In some regions, and depending on the bow-shock geometry, these can be observed on several scales, and show the typical signatures of magnetohydrodynamic turbulence. Using Cluster data, magnetic field spectra and flatness are observed in two intervals separated by a sharp transition from quasi-parallel to quasi-perpendicular magnetic field with respect to the bow-shock normal. The multifractal generalized dimensions D-q and the corresponding multifractal spectrum f(alpha) were estimated using a coarse-graining method. A p-model fit was used to obtain a single parameter to describe quantitatively the strength of multifractality and intermittency. Results show a clear transition and sharp differences in the intermittency properties for the two regions, with the quasi-parallel turbulence being more intermittent.

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  • 22.
    Kilpua, E. K. J.
    et al.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Fontaine, D.
    PSL Res Univ, Univ Paris Saclay, Univ Paris Sud,Observ Paris, Lab Phys Plasmas,Ecole Polytech,CNRS,Sorbonne Uni, Palaiseau, France.
    Moissard, C.
    PSL Res Univ, Univ Paris Saclay, Univ Paris Sud,Observ Paris, Lab Phys Plasmas,Ecole Polytech,CNRS,Sorbonne Uni, Palaiseau, France.
    Ala-Lahti, M.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Palmerio, E.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Good, S. W.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Kalliokoski, M. M. H.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Lumme, E.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Osmane, A.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Palmroth, M.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Turc, L.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Solar Wind Properties and Geospace Impact of Coronal Mass Ejection-Driven Sheath Regions: Variation and Driver Dependence2019In: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 17, no 8, p. 1257-1280Article in journal (Refereed)
    Abstract [en]

    We present a statistical study of interplanetary conditions and geospace response to 89 coronal mass ejection-driven sheaths observed during Solar Cycles 23 and 24. We investigate in particular the dependencies on the driver properties and variations across the sheath. We find that the ejecta speed principally controls the sheath geoeffectiveness and shows the highest correlations with sheath parameters, in particular in the region closest to the shock. Sheaths of fast ejecta have on average high solar wind speeds, magnetic (B) field magnitudes, and fluctuations, and they generate efficiently strong out-of-ecliptic fields. Slow-ejecta sheaths are considerably slower and have weaker fields and field fluctuations, and therefore they cause primarily moderate geospace activity. Sheaths of weak and strong B field ejecta have distinct properties, but differences in their geoeffectiveness are less drastic. Sheaths of fast and strong ejecta push the subsolar magnetopause significantly earthward, often even beyond geostationary orbit. Slow-ejecta sheaths also compress the magnetopause significantly due to their large densities that are likely a result of their relatively long propagation times and source near the streamer belt. We find the regions near the shock and ejecta leading edge to be the most geoeffective parts of the sheath. These regions are also associated with the largest B field magnitudes, out-of-ecliptic fields, and field fluctuations as well as largest speeds and densities. The variations, however, depend on driver properties. Forecasting sheath properties is challenging due to their variable nature, but the dependence on ejecta properties determined in this work could help to estimate sheath geoeffectiveness through remote-sensing coronal mass ejection observations.

  • 23.
    Kilpua, E. K. J.
    et al.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Good, S. W.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Ala-Lahti, M.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Osmane, A.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Fontaine, D.
    PSL Res Univ, Inst Polytech Paris, Observ Paris,LPP, Univ Paris Saclay,Sorbonne Univ,Ecole Polytech,CN, Palaiseau, France.
    Hadid, L.
    PSL Res Univ, Inst Polytech Paris, Observ Paris,LPP, Univ Paris Saclay,Sorbonne Univ,Ecole Polytech,CN, Palaiseau, France.
    Janvier, M.
    Univ Paris Saclay, CNRS, Inst Astrophys Spatiale, Orsay.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Statistical Analysis of Magnetic Field Fluctuations in Coronal Mass Ejection-Driven Sheath Regions2021In: Frontiers in Astronomy and Space Sciences, E-ISSN 2296-987X, Vol. 7, article id 610278Article in journal (Refereed)
    Abstract [en]

    We report a statistical analysis of magnetic field fluctuations in 79 coronal mass ejection- (CME-) driven sheath regions that were observed in the near-Earth solar wind. Wind high-resolution magnetic field data were used to investigate 2 h regions adjacent to the shock and ejecta leading edge (Near-Shock and Near-LE regions, respectively), and the results were compared with a 2 h region upstream of the shock. The inertial-range spectral indices in the sheaths are found to be mostly steeper than the Kolmogorov −5/3 index and steeper than in the solar wind ahead. We did not find indications of an ƒ−1 spectrum, implying that magnetic fluctuation properties in CME sheaths differ significantly from planetary magnetosheaths and that CME-driven shocks do not reset the solar wind turbulence, as appears to happen downstream of planetary bow shocks. However, our study suggests that new compressible fluctuations are generated in the sheath for a wide variety of shock/upstream conditions. Fluctuation properties particularly differed between the Near-Shock region and the solar wind ahead. A strong positive correlation in the mean magnetic compressibility was found between the upstream and downstream regions, but the compressibility values in the sheaths were similar to those in the slow solar wind (<0.2), regardless of the value in the preceding wind. However, we did not find clear correlations between the inertial-range spectral indices in the sheaths and shock/preceding solar wind properties, nor with the mean normalized fluctuation amplitudes. Correlations were also considerably lower in the Near-LE region than in the Near-Shock region. Intermittency was also considerably higher in the sheath than in the upstream wind according to several proxies, particularly so in the Near-Shock region. Fluctuations in the sheath exhibit larger rotations than upstream, implying the presence of strong current sheets in the sheath that can add to intermittency.

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  • 24.
    Kilpua, Emilia K. J.
    et al.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Fontaine, Dominique
    PSL Res Univ, Inst Polytech Paris, Univ Paris Saclay, LPP,CNRS,Ecole Polytech,Sorbonne Univ,Observ Pari, Palaiseau, France..
    Good, Simon W.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Ala-Lahti, Matti
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Osmane, Adnane
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Palmerio, Erika
    Univ Helsinki, Dept Phys, Helsinki, Finland.;Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Moissard, Clement
    PSL Res Univ, Inst Polytech Paris, Univ Paris Saclay, LPP,CNRS,Ecole Polytech,Sorbonne Univ,Observ Pari, Palaiseau, France..
    Hadid, Lina Z
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. PSL Res Univ, Inst Polytech Paris, Univ Paris Saclay, LPP,CNRS,Ecole Polytech,Sorbonne Univ,Observ Pari, European Space Agcy, Estec, Noordwijk, Netherlands..
    Janvier, Miho
    Univ Paris Saclay, Univ Paris Sud, CNRS, Inst Astrophys Spatiale, Orsay, France..
    Magnetic field fluctuation properties of coronal mass ejection-driven sheath regions in the near-Earth solar wind2020In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 38, no 5, p. 999-1017Article in journal (Refereed)
    Abstract [en]

    In this work, we investigate magnetic field fluctuations in three coronal mass ejection (CME)-driven sheath regions at 1 AU, with their speeds ranging from slow to fast. The data set we use consists primarily of high-resolution (0.092 s) magnetic field measurements from the Wind spacecraft. We analyse magnetic field fluctuation amplitudes, compressibility, and spectral properties of fluctuations. We also analyse intermittency using various approaches; we apply the partial variance of increments (PVIs) method, investigate probability distribution functions of fluctuations, including their skewness and kurtosis, and perform a structure function analysis. Our analysis is conducted separately for three different subregions within the sheath and one in the solar wind ahead of it, each 1 h in duration. We find that, for all cases, the transition from the solar wind ahead to the sheath generates new fluctuations, and the intermittency and compressibility increase, while the region closest to the ejecta leading edge resembled the solar wind ahead. The spectral indices exhibit large variability in different parts of the sheath but are typically steeper than Kolmogorov's in the inertial range. The structure function analysis produced generally the best fit with the extended p model, suggesting that turbulence is not fully developed in CME sheaths near Earth's orbit. Both Kraichnan-Iroshinikov and Kolmogorov's forms yielded high intermittency but different spectral slopes, thus questioning how well these models can describe turbulence in sheaths. At the smallest timescales investigated, the spectral indices indicate shallower than expected slopes in the dissipation range (between 2 and 2 :5), suggesting that, in CME-driven sheaths at 1 AU, the energy cascade from larger to smaller scales could still be ongoing through the ion scale. Many turbulent properties of sheaths (e.g. spectral indices and compressibility) resemble those of the slow wind rather than the fast. They are also partly similar to properties reported in the terrestrial magnetosheath, in particular regarding their intermittency, compressibility, and absence of Kolmogorov's type turbulence. Our study also reveals that turbulent properties can vary considerably within the sheath. This was particularly the case for the fast sheath behind the strong and quasi-parallel shock, including a small, coherent structure embedded close to its midpoint. Our results support the view of the complex formation of the sheath and different physical mechanisms playing a role in generating fluctuations in them.

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  • 25.
    Perri, S.
    et al.
    Univ Calabria, Dipartimento Fis, Via P Bucci 87036, Arcavacata Di Rende, Italy.
    Perrone, D.
    ASI Italian Space Agcy, Via Politecn Snc, Rome, Italy.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Sorriso-Valvo, L.
    Escuela Politec Nacl, Dept Fis, Av Ladron de Guevara 253, Quito 170517, Ecuador;CNR, ISTP, Via Amendola 122-D, I-70126 Bari, Italy.
    Paterson, W. R.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.
    Pollock, C. J.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.
    Dorelli, J. C.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.
    Avanov, L. A.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.
    Lavraud, B.
    Univ Toulouse, CNES, UPS, Inst Rech Astrophys & Planetol,CNRS, 9 Ave Colonel Roche, F-31400 Toulouse, France.
    Saito, Y.
    JAXA, Tokyo 1828522, Japan.
    Nakamura, R.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria.
    Fischer, D.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria.
    Baumjohann, W.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria.
    Plaschke, F.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria.
    Narita, Y.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria.
    Magnes, W.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria.
    Russell, C. T.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, 603 CE Young Dr East, Los Angeles, CA 90095 USA.
    Strangeway, R. J.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, 603 CE Young Dr East, Los Angeles, CA 90095 USA.
    Le Contel, O.
    Univ Paris Sud, Sorbonne Univ, Ecole Polytech, Observ Paris,Lab Phys Plasmas,CNRS, Route Saclay, F-91128 Palaiseaux, France.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Valentini, F.
    Univ Calabria, Dipartimento Fis, Via P Bucci 87036, Arcavacata Di Rende, Italy.
    On the deviation from Maxwellian of the ion velocity distribution functions in the turbulent magnetosheath2020In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 86, no 1, article id 905860108Article in journal (Refereed)
    Abstract [en]

    The deviation from thermodynamic equilibrium of the ion velocity distribution functions (VDFs), as measured by the Magnetospheric Multiscale (MMS) mission in the Earth's turbulent magnetosheath, is quantitatively investigated. Making use of the unprecedented high-resolution MMS ion data, and together with Vlasov-Maxwell simulations, this analysis aims at investigating the relationship between deviation from Maxwellian equilibrium and typical plasma parameters. Correlations of the non-Maxwellian features with plasma quantities such as electric fields, ion temperature, current density and ion vorticity are found to be similar in magnetosheath data and numerical experiments, with a poor correlation between distortions of ion VDFs and current density, evidence that questions the occurrence of VDF departure from Maxwellian at the current density peaks. Moreover, strong correlation has been observed with the magnitude of the electric field in the turbulent magnetosheath, while a certain degree of correlation has been found in the numerical simulations and during a magnetopause crossing by MMS. This work could help shed light on the influence of electrostatic waves on the distortion of the ion VDFs in space turbulent plasmas.

  • 26.
    Perri, Silvia
    et al.
    Univ Calabria, Dipartimento Fis, Ponte P Bucci Cubo 31C, I-87036 Arcavacata Di Rende, Italy..
    Perrone, Denise
    ASI Italian Space Agcy, Via Politecn SNC, I-00133 Rome, Italy..
    Roberts, Owen
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria..
    Settino, Adriana
    Univ Calabria, Dipartimento Fis, Ponte P Bucci Cubo 31C, I-87036 Arcavacata Di Rende, Italy..
    Yordanova, Emiliya
    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, Ist Sci & Tecnol Plasmi, Via Amendola 122-D, I-70126 Bari, Italy..
    Veltri, Pierluigi
    Univ Calabria, Dipartimento Fis, Ponte P Bucci Cubo 31C, I-87036 Arcavacata Di Rende, Italy..
    Valentini, Francesco
    Univ Calabria, Dipartimento Fis, Ponte P Bucci Cubo 31C, I-87036 Arcavacata Di Rende, Italy..
    Nature of Electrostatic Fluctuations in the Terrestrial Magnetosheath2021In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 919, no 2, article id 75Article in journal (Refereed)
    Abstract [en]

    The high cadence plasma, electric, and magnetic field measurements by the Magnetospheric MultiScale spacecraft allow us to explore the near-Earth space plasma with an unprecedented time and spatial resolution, resolving electron-scale structures that naturally emerge from plasma complex dynamics. The formation of small-scale turbulent features is often associated to structured, non-Maxwellian particle velocity distribution functions that are not at thermodynamic equilibrium. Using measurements in the terrestrial magnetosheath, this study focuses on regions presenting bumps in the power spectral density of the parallel electric field at subproton scales. Correspondingly, it is found that the ion velocity distribution functions exhibit beam-like features at nearly the local ion thermal speed. Ion-cyclotron waves in the ion-scale range are frequently observed at the same locations. These observations, supported by numerical simulations, are consistent with the generation of ion-bulk waves that propagate at the ion thermal speed. This represents a new branch of efficient energy transfer at small scales, which may be relevant to weakly collisional astrophysical plasmas.

  • 27.
    Perri, Silvia
    et al.
    Univ Calabria, Dept Phys, Arcavacata Di Rende, Italy..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Puzzarini, Cristina
    Univ Bologna, Dept Chem Giacomo Ciamician, Bologna, Italy..
    Editorial: Women in science: astronomy and space sciences2024In: Frontiers in Astronomy and Space Sciences, E-ISSN 2296-987X, Vol. 11, article id 1378816Article in journal (Other academic)
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  • 28.
    Quijia, Paulina
    et al.
    Univ Calabria, Dipartamento Fis, Cubo 31C, I-87036 Arcavacata Di Rende, Italy.;Escuela Politec Nacl, Dept Fis, Av Ladron de Guevara E11-253, Quito 170525, Ecuador..
    Fraternale, Federico
    Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35805 USA..
    Stawarz, Julia E.
    Imperial Coll London, Dept Phys, London SW7 2BU, England..
    Vasconez, Christian L.
    Escuela Politec Nacl, Dept Fis, Av Ladron de Guevara E11-253, Quito 170525, Ecuador..
    Perri, Silvia
    Univ Calabria, Dipartamento Fis, Cubo 31C, I-87036 Arcavacata Di Rende, Italy..
    Marino, Raffaele
    Univ Claude Bernard Lyon 1, Lab Mecan Fluides & Acoust, INSA Lyon, Ecole Cent Lyon,CNRS, F-69134 Ecully, France..
    Yordanova, Emiliya
    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, Ist Sci & Tecnol Plasmi, Via Amendola 122-D, I-70126 Bari, Italy..
    Comparing turbulence in a Kelvin-Helmholtz instability region across the terrestrial magnetopause2021In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 503, no 4, p. 4815-4827Article in journal (Refereed)
    Abstract [en]

    The properties of turbulence observed within the plasma originating from the magnetosheath and the magnetospheric boundary layer, which have been entrained within vortices driven by the Kelvin-Helmholtz Instability (KHI), are compared. The goal of such a study is to determine similarities and differences between the two different regions. In particular, we study spectra, intermittency and the third-order moment scaling, as well as the distribution of a local energy transfer rate proxy. The analysis is performed using the Magnetospheric Multiscale data from a single satellite that crosses longitudinally the KHI. Two sets of regions, one set containing predominantly magnetosheath plasma and the other containing predominantly magnetospheric plasma, are analysed separately, thus allowing us to explore turbulence properties in two portions of very different plasma samples. Results show that the dynamics in the two regions is different, with the boundary layer plasma presenting a shallower spectra and larger energy transfer rate, indicating an early stage of turbulence. In both regions, the effect of the KHI is evidenced.

  • 29.
    Richard, Louis
    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, Space Plasma Physics.
    Sorriso-Valvo, Luca
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. CNR/ISTP—Istituto per la Scienza e la Tecnologia dei Plasmi, 70126 Bari, Italy; Space and Plasma Physics, School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Stockholm, Sweden.
    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.
    Turbulence in Magnetic Reconnection Jets from Injection to Sub-Ion Scales2024In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 132, no 10, article id 105201Article in journal (Refereed)
    Abstract [en]

    We investigate turbulence in magnetic reconnection jets in the Earth’s magnetotail using data from the Magnetospheric Multiscale spacecraft. We show that signatures of a limited inertial range are observed in many reconnection jets. The observed turbulence develops on the timescale of a few ion gyroperiods, resulting in intermittent multifractal energy cascade from the characteristic scale of the jet down to the ion scales. We show that at sub-ion scales, the fluctuations are close to monofractal and predominantly kinetic Alfvén waves. The observed energy transfer rate across the inertial range is ∼108  J kg−1 s−1, which is the largest reported for space plasmas so far.

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  • 30.
    Sorriso-Valvo, Luca
    et al.
    Escuela Politecn Natl, Dept Fis, Quito, Ecuador;CNR, ISTP, Bari, Italy.
    De Vita, Gaetano
    CNR, ISTP, Bari, Italy.
    Fraternale, Federico
    Politecn Torino, Dipartimento Sci Applicata & Tecnol, Turin, Italy.
    Gurchumelia, Alexandre
    Iv Javakhishvili Tbilisi State Univ, M Nadia Inst Geophys, Tbilisi, Georgia.
    Perri, Silvia
    Univ Calabria, Dipartimento Fis, Arcavacata Di Rende, Italy.
    Nigro, Giuseppina
    Univ Calabria, Dipartimento Fis, Arcavacata Di Rende, Italy.
    Catapano, Filomena
    Serco Italia ESA ESRIN, Frascati, Italy.
    Retino, Alessandro
    Sorbonne Univ, Ecole Poliechn, LPP CNRS, Paris, France.
    Chen, Christopher H. K.
    Queen Mary Univ London, Sch Phys & Astron, London, England.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Pezzi, Oreste
    Gran Sasso Sci Inst, Laquila, Italy;INFN, Lab Nazl Gran Sasso, Assergi, Italy.
    Chargazia, Khatuna
    Iv Javakhishvili Tbilisi State Univ, M Nadia Inst Geophys, Tbilisi, Georgia;Iv Javakhishvili Tbilisi State Univ, I Vekua Inst Appl Math, Tbilisi, Georgia.
    Kharshiladze, Oleg
    Iv Javakhishvili Tbilisi State Univ, M Nadia Inst Geophys, Tbilisi, Georgia.
    Kvaratskhelia, Diana
    Iv Javakhishvili Tbilisi State Univ, M Nadia Inst Geophys, Tbilisi, Georgia;Sokhumi State Univ, Tbilisi, Georgia.
    Vsconez, Christian L.
    Escuela Politecn Natl, Dept Fis, Quito, Ecuador.
    Marino, Raffaele
    Univ Claude Bernard Lyon, Ecole Cent Lyon, Lab Mecan Fluides & Acoust, CNRS,INSA Lyon, Ecully, France.
    Le Contel, Olivier
    Sorbonne Univ, Ecole Poliechn, LPP CNRS, Paris, France.
    Giles, Barbara
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Moore, Thomas E.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Torbert, Roy B.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.
    Burch, James L.
    Southwest Res Inst, San Antonio, TX USA.
    Sign Singularity of the Local Energy Transfer in Space Plasma Turbulence2019In: Frontiers in Physics, E-ISSN 2296-424X, Vol. 7, article id 108Article in journal (Refereed)
    Abstract [en]

    In weakly collisional space plasmas, the turbulent cascade provides most of the energy that is dissipated at small scales by various kinetic processes. Understanding the characteristics of such dissipative mechanisms requires the accurate knowledge of the fluctuations that make energy available for conversion at small scales, as different dissipation processes are triggered by fluctuations of a different nature. The scaling properties of different energy channels are estimated here using a proxy of the local energy transfer, based on the third-order moment scaling law for magnetohydrodynamic turbulence. In particular, the sign-singularity analysis was used to explore the scaling properties of the alternating positive-negative energy fluxes, thus providing information on the structure and topology of such fluxes for each of the different type of fluctuations. The results show the highly complex geometrical nature of the flux, and that the local contributions associated with energy and cross-helicity non-linear transfer have similar scaling properties. Consequently, the fractal properties of current and vorticity structures are similar to those of the Alfvenic fluctuations.

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  • 31.
    Sorriso-Valvo, Luca
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. CNR, Ist Sci & Tecnol Plasmi, Via Amendola 122-D, I-70126 Bari, Italy.;KTH Royal Inst Technol, Sch Elect Engn & Comp Sci, Space & Plasma Phys, Teknikringen 31, S-11428 Stockholm, Sweden..
    Marino, R.
    Univ Claude Bernard Lyon 1, Univ Lyon, Ecole Cent Lyon, CNRS,INSA Lyon,Lab Mecan Fluides & Acoust,UMR5509, F-69134 Ecully, France..
    Foldes, R.
    Univ Claude Bernard Lyon 1, Univ Lyon, Ecole Cent Lyon, CNRS,INSA Lyon,Lab Mecan Fluides & Acoust,UMR5509, F-69134 Ecully, France.;Univ Aquila, Dipartimento Sci Fis & Chim, Via Vetoio 42, I-67100 Coppito, AQ, Italy..
    Leveque, E.
    Univ Claude Bernard Lyon 1, Univ Lyon, Ecole Cent Lyon, CNRS,INSA Lyon,Lab Mecan Fluides & Acoust,UMR5509, F-69134 Ecully, France..
    D'Amicis, R.
    Natl Inst Astrophys INAF, Inst Space Astrophys & Planetol IAPS, Via Fosso Cavaliere 100, I-00133 Rome, Italy..
    Bruno, R.
    Natl Inst Astrophys INAF, Inst Space Astrophys & Planetol IAPS, Via Fosso Cavaliere 100, I-00133 Rome, Italy..
    Telloni, D.
    Natl Inst Astrophys INAF, Astrophys Observ Torino, Via Osservatorio 20, I-10025 Pino Torinese, Italy..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Helios 2 observations of solar wind turbulence decay in the inner heliosphere2023In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 672, article id A13Article in journal (Refereed)
    Abstract [en]

    Aims: A linear scaling of the mixed third-order moment of the magnetohydrodynamic (MHD) fluctuations is used to estimate the energy transfer rate of the turbulent cascade in the expanding solar wind.

    Methods: In 1976, the Helios 2 spacecraft measured three samples of fast solar wind originating from the same coronal hole, at different distances from the Sun. Along with the adjacent slow solar wind streams, these intervals represent a unique database for studying the radial evolution of turbulence in samples of undisturbed solar wind. A set of direct numerical simulations of the MHD equations performed with the Lattice-Boltzmann code FLAME was also used for interpretation.

    Results: We show that the turbulence energy transfer rate decays approximately as a power law of the distance and that both the amplitude and decay law correspond to the observed radial temperature profile in the fast wind case. Results from MHD numerical simulations of decaying MHD turbulence show a similar trend for the total dissipation, suggesting an interpretation of the observed dynamics in terms of decaying turbulence and that multi-spacecraft studies of the solar wind radial evolution may help clarify the nature of the evolution of the turbulent fluctuations in the ecliptic solar wind.

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  • 32.
    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.

  • 33.
    Steinvall, Konrad
    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, Space Plasma Physics.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cozzani, Giulia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaivads, A.
    KTH Royal Inst Technol, Sch Elect Engn & Comp Sci, Div Space & Plasma Phys, S-11428 Stockholm, Sweden..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    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.
    Maksimovic, M.
    Univ Paris Diderot, Sorbonne Univ, CNRS, Observ Paris,Univ PSL,LESIA, Sorbonne Paris Cite,5 Pl Jules Janssen, F-92195 Meudon, France..
    Bale, S. D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.;Univ Calif Berkeley, Phys Dept, Berkeley, CA 94720 USA..
    Chust, T.
    Univ Paris Saclay, Sorbonne Univ, Observ Paris, Ecole Polytech,LPP,CNRS, Paris, France..
    Krasnoselskikh, V.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.;CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France..
    Kretzschmar, M.
    CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France.;Univ Orleans, Orleans, France..
    Lorfèvre, E.
    CNES, 18 Ave Edouard Belin, F-31400 Toulouse, France..
    Plettemeier, D.
    Tech Univ Dresden, Helmholtz Str 10, D-01187 Dresden, Germany..
    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..
    Vecchio, A.
    Univ Paris Diderot, Sorbonne Univ, CNRS, Observ Paris,Univ PSL,LESIA, Sorbonne Paris Cite,5 Pl Jules Janssen, F-92195 Meudon, France.;Radboud Univ Nijmegen, Dept Astrophys, Radboud Radio Lab, Nijmegen, Netherlands..
    Horbury, T. S.
    Imperial Coll London, South Kensington Campus, London SW7 2AZ, England..
    O'Brien, H.
    Imperial Coll London, South Kensington Campus, London SW7 2AZ, England..
    Evans, V.
    Imperial Coll London, South Kensington Campus, London SW7 2AZ, England..
    Fedorov, A.
    Inst Rech Astrophys & Planetol, 9 Ave Colonel Roche,BP 4346, F-31028 Toulouse 4, France..
    Louarn, P.
    Inst Rech Astrophys & Planetol, 9 Ave Colonel Roche,BP 4346, F-31028 Toulouse 4, France..
    Génot, V.
    Inst Rech Astrophys & Planetol, 9 Ave Colonel Roche,BP 4346, F-31028 Toulouse 4, France..
    André, N.
    Inst Rech Astrophys & Planetol, 9 Ave Colonel Roche,BP 4346, F-31028 Toulouse 4, France..
    Lavraud, B.
    Inst Rech Astrophys & Planetol, 9 Ave Colonel Roche,BP 4346, F-31028 Toulouse 4, France.;Univ Bordeaux, Lab Astrophys Bordeaux, CNRS, Pessac, France..
    Rouillard, A. P.
    Inst Rech Astrophys & Planetol, 9 Ave Colonel Roche,BP 4346, F-31028 Toulouse 4, France..
    Owen, C. J.
    Univ Coll London, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England..
    Solar wind current sheets and deHoffmann-Teller analysis: First results from Solar Orbiter's DC electric field measurements2021In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 656, article id A9Article in journal (Refereed)
    Abstract [en]

    Context. Solar Orbiter was launched on 10 February 2020 with the purpose of investigating solar and heliospheric physics using a payload of instruments designed for both remote and in situ studies. Similar to the recently launched Parker Solar Probe, and unlike earlier missions, Solar Orbiter carries instruments designed to measure low-frequency DC electric fields.

    Aims. In this paper, we assess the quality of the low-frequency DC electric field measured by the Radio and Plasma Waves instrument (RPW) on Solar Orbiter. In particular, we investigate the possibility of using Solar Orbiter’s DC electric and magnetic field data to estimate the solar wind speed.

    Methods. We used a deHoffmann-Teller (HT) analysis, based on measurements of the electric and magnetic fields, to find the velocity of solar wind current sheets, which minimises a single component of the electric field. By comparing the HT velocity to the proton velocity measured by the Proton and Alpha particle Sensor (PAS), we have developed a simple model for the effective antenna length, Leff of the E-field probes. We then used the HT method to estimate the speed of the solar wind.

    Results. Using the HT method, we find that the observed variations in Ey are often in excellent agreement with the variations in the magnetic field. The magnitude of Ey, however, is uncertain due to the fact that the Leff depends on the plasma environment. Here, we derive an empirical model relating Leff to the Debye length, which we can use to improve the estimate of Ey and, consequently, the estimated solar wind speed.

    Conclusions. The low-frequency electric field provided by RPW is of high quality. Using the deHoffmann-Teller analysis, Solar Orbiter’s magnetic and electric field measurements can be used to estimate the solar wind speed when plasma data are unavailable.

  • 34.
    Svenningsson, Ida
    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.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cozzani, G.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Khotyaintsev, Yuri V.
    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. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Kinetic Generation of Whistler Waves in the Turbulent Magnetosheath2022In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 49, no 15, article id e2022GL099065Article in journal (Refereed)
    Abstract [en]

    The Earth's magnetosheath (MSH) is governed by numerous physical processes which shape the particle velocity distributions and contribute to the heating of the plasma. Among them are whistler waves which can interact with electrons. We investigate whistler waves detected in the quasi-parallel MSH by NASA's Magnetospheric Multiscale mission. We find that the whistler waves occur even in regions that are predicted stable to wave growth by electron temperature anisotropy. Whistlers are observed in ion-scale magnetic minima and are associated with electrons having butterfly-shaped pitch-angle distributions. We investigate in detail one example and, with the support of modeling by the linear numerical dispersion solver Waves in Homogeneous, Anisotropic, Multicomponent Plasmas, we demonstrate that the butterfly distribution is unstable to the observed whistler waves. We conclude that the observed waves are generated locally. The result emphasizes the importance of considering complete 3D particle distribution functions, and not only the temperature anisotropy, when studying plasma wave instabilities.

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  • 35.
    Svenningsson, Ida
    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.
    Yordanova, Emiliya
    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.
    André, Mats
    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.
    Cozzani, G.
    Department of Physics, University of Helsinki, Helsinki, Finland.
    Whistler wave occurrence in the magnetosheath: comparing the quasi-parallel and quasi-perpendicular geometriesManuscript (preprint) (Other academic)
  • 36.
    Svenningsson, Ida
    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.
    Yordanova, Emiliya
    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.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cozzani, G.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Steinvall, K.
    Univ Southampton, Sch Phys & Astron, Southampton, England..
    Whistler Waves in the Quasi-Parallel and Quasi-Perpendicular Magnetosheath2024In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 129, no 6, article id e2024JA032661Article in journal (Refereed)
    Abstract [en]

    In the Earth's magnetosheath (MSH), several processes contribute to energy dissipation and plasma heating, one of which is wave-particle interactions between whistler waves and electrons. However, the overall impact of whistlers on electron dynamics in the MSH remains to be quantified. We analyze 18 hr of burst-mode measurements from the Magnetospheric Multiscale (MMS) mission, including data from the unbiased magnetosheath campaign during February-March 2023. We present a statistical study of 34,409 whistler waves found using automatic detection. We compare wave occurrence in the different MSH geometries and find three times higher occurrence in the quasi-perpendicular MSH compared to the quasi-parallel case. We also study the wave properties and find that the waves propagate quasi-parallel to the background magnetic field, have a median frequency of 0.2 times the electron cyclotron frequency, median amplitude of 0.03-0.06 nT (30-60 pT), and median duration of a few tens of wave periods. The whistler waves are preferentially observed in local magnetic dips and density peaks and are not associated with an increased temperature anisotropy. Also, almost no whistlers are observed in regions with parallel electron plasma beta lower than 0.1. Importantly, when estimating pitch-angle diffusion times we find that the whistler waves cause significant pitch-angle scattering of electrons in the MSH. Whistlers exist throughout the magnetosheath with higher occurrence in the quasi-perpendicular geometry and in local magnetic field dips Whistlers are observed in regions with electron beta above 0.1 and are not correlated with electron temperature anisotropy Whistlers cause significant pitch-angle scattering of magnetosheath electrons

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  • 37.
    Telloni, Daniele
    et al.
    Astrophys Observ Torino, Natl Inst Astrophys, Pino Torinese, Italy..
    Voeroes, Zoltan
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Swedish Inst Space Phys, Uppsala, Sweden..
    D'Amicis, Raffaella
    Inst Space Astrophys & Planetol, Natl Inst Astrophys, Rome, Italy..
    Editorial: Magnetic Connectivity of the Earth and Planetary Environments to the Sun in Space Weather Studies2022In: Frontiers in Astronomy and Space Sciences, E-ISSN 2296-987X, Vol. 9, article id 853925Article in journal (Other academic)
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  • 38.
    Voeroes, Zoltan
    et al.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.;Inst Earth Phys & Space Sci, Sopron, Hungary..
    Roberts, Owen W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Yordanova, Emiliya
    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, Bari, Italy.;KTH Royal Inst Technol, Sch Elect Engn & Comp Sci, Space & Plasma Phys, Stockholm, Sweden..
    Nakamura, Rumi
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Narita, Yasuhito
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Schmid, Daniel
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Plaschke, Ferdinand
    TUBraunschweig, Inst Geophys & Extraterr Phys, Braunschweig, Germany..
    Kis, Arpad
    Inst Earth Phys & Space Sci, Sopron, Hungary..
    How to improve our understanding of solar wind-magnetosphere interactions on the basis of the statistical evaluation of the energy budget in the magnetosheath?2023In: Frontiers in Astronomy and Space Sciences, E-ISSN 2296-987X, Vol. 10, article id 1163139Article in journal (Refereed)
    Abstract [en]

    Solar wind (SW) quantities, referred to as coupling parameters (CPs), are often used in statistical studies devoted to the analysis of SW-magnetosphere-ionosphere couplings. Here, the CPs and their limitations in describing the magnetospheric response are reviewed. We argue that a better understanding of SW magnetospheric interactions could be achieved through estimations of the energy budget in the magnetosheath (MS), which is the interface region between the SW and magnetosphere. The energy budget involves the energy transfer between scales, energy transport between locations, and energy conversions between electromagnetic, kinetic, and thermal energy channels. To achieve consistency with the known multi-scale complexity in the MS, the energy terms have to be complemented with kinetic measures describing some aspects of ion-electron scale physics.

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  • 39.
    Voeroes, Zoltan
    et al.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.;Eotvos Lorand Res Network, Inst Earth Phys & Space Sci, Sopron, Hungary..
    Varsani, Ali
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Sasunov, Yury L.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.;Univ Vienna, Dept Astrophys, Vienna, Austria.;Lomonosov Moscow State Univ, Skobeltsyn Inst Nucl Phys, Moscow, Russia..
    Roberts, Owen W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Kis, Arpad
    Eotvos Lorand Res Network, Inst Earth Phys & Space Sci, Sopron, Hungary..
    Nakamura, Rumi
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Narita, Yasuhito
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Magnetic Reconnection Within the Boundary Layer of a Magnetic Cloud in the Solar Wind2021In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 126, no 9, article id e2021JA029415Article in journal (Refereed)
    Abstract [en]

    The twisted local magnetic field at the front or rear regions of the magnetic clouds (MCs) associated with interplanetary coronal mass ejections (ICMEs) is often nearly opposite to the direction of the ambient interplanetary magnetic field. There is also observational evidence for magnetic reconnection (MR) outflows occurring within the boundary layers of MCs. In this study, a MR event located at the western flank of the MC occurring on October 3, 2000 is studied in detail. Both the large-scale geometry of the helical MC and the MR outflow structure are scrutinized in a detailed multipoint study. The ICME sheath is of hybrid propagation-expansion type. Here, the freshly reconnected open field lines are expected to slip slowly over the MC resulting in plasma mixing at the same time. As for MR, the current sheet geometry and the vertical motion of the outflow channel between ACE-Geotail-WIND spacecraft were carefully studied and tested. The main findings on MR include (a) first-time observation of non-Petschek-type slow-shock-like discontinuities in the inflow regions; (b) observation of turbulent Hall magnetic field associated with a Lorentz-force-deflected electron jet; (c) acceleration of protons by reconnection electric field and their back-scatter from the slow-shock-like discontinuity; (d) observation of relativistic electron near the MC inflow boundary/separatrix; these electron populations can presumably appear as a result of nonadiabatic acceleration, gradient B drift, and via acceleration in the electrostatic potential well associated with the Hall current system; and (e) observation of Doppler-shifted ion-acoustic and Langmuir waves in the MC inflow region.

  • 40.
    Voeroes, Zoltan
    et al.
    Austrian Acad Sci, Space Res Inst, A-8010 Graz, Austria.;Eotvos Lorand Univ, Dept Geophys & Space Sci, Budapest, Hungary..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Echim, Marius M.
    Belgian Inst Space Aeron, Brussels, Belgium.;Inst Space Sci, Magurele, Romania..
    Consolini, Giuseppe
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy..
    Narita, Yasuhito
    Austrian Acad Sci, Space Res Inst, A-8010 Graz, Austria..
    Turbulence-Generated Proton-Scale Structures In The Terrestrial Magnetosheath2016In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 819, no 1, article id L15Article in journal (Refereed)
    Abstract [en]

    Recent results of numerical magnetohydrodynamic simulations suggest that in collisionless space plasmas, turbulence can spontaneously generate thin current sheets. These coherent structures can partially explain the intermittency and the non-homogenous distribution of localized plasma heating in turbulence. In this Letter, Cluster multi-point observations are used to investigate the distribution of magnetic field discontinuities and the associated small-scale current sheets in the terrestrial magnetosheath downstream of a quasi-parallel bow shock. It is shown experimentally, for the first time, that the strongest turbulence-generated current sheets occupy the long tails of probability distribution functions associated with extremal values of magnetic field partial derivatives. During the analyzed one-hour time interval, about a hundred strong discontinuities, possibly proton-scale current sheets, were observed.

  • 41.
    Voros, Z.
    et al.
    Karl Franzens Univ Graz, Inst Phys, Graz, Austria.;Austrian Acad Sci, Space Res Inst, Graz, Austria.;Hungarian Acad Sci, RCAES, Geodet & Geophys Inst, Sopron, Hungary..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Varsani, A.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.;UCL, Mullard Space Sci Lab, Dorking, Surrey, England..
    Genestreti, K. J.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Li, Wenya
    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.
    Norgren, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Nakamura, R.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Narita, Y.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Plaschke, F.
    Karl Franzens Univ Graz, Inst Phys, Graz, Austria.;Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Magnes, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Baumjohann, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Fischer, D.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Elin
    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.
    Lindqvist, P. -A
    Space and Plasma Group, Royal Institute of Technology, Stockholm, Sweden..
    Marklund, G.
    Royal Inst Technol, Space & Plasma Grp, Stockholm, Sweden..
    Ergun, R. E.
    Univ Colorado Boulder, Lab Atmospher & Space Phys, Boulder, CO USA..
    Leitner, M.
    Karl Franzens Univ Graz, Inst Phys, Graz, Austria..
    Leubner, M. P.
    Univ Innsbruck, Inst Astro & Particle Phys, Innsbruck, Austria..
    Strangeway, R. J.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA USA..
    Le Contel, O.
    UPMC, Univ Paris Sud, CNRS, Ecole Polytech,Lab Phys Plasmas,Obs Paris, Paris, France..
    Pollock, C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Giles, B. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Torbert, R. B.
    Southwest Research Institute, San Antonio, TX, USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Avanov, L. A.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Dorelli, J. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.;Univ Maryland, Astron Dept, College Pk, MD 20742 USA..
    Paterson, W. R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Lavraud, B.
    Univ Toulouse, UPS, CNRS, CNES,IRAP, Toulouse, France..
    Saito, Y.
    JAXA, Chofu, Tokyo, Japan..
    MMS Observation of Magnetic Reconnection in the Turbulent Magnetosheath2017In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 11, p. 11442-11467Article in journal (Refereed)
    Abstract [en]

    In this paper we use the full armament of the MMS (Magnetospheric Multiscale) spacecraft to study magnetic reconnection in the turbulent magnetosheath downstream of a quasi-parallel bow shock. Contrarily to the magnetopause and magnetotail cases, only a few observations of reconnection in the magnetosheath have been reported. The case study in this paper presents, for the first time, both fluid-scale and kinetic-scale signatures of an ongoing reconnection in the turbulent magnetosheath. The spacecraft are crossing the reconnection inflow and outflow regions and the ion diffusion region (IDR). Inside the reconnection outflows D shape ion distributions are observed. Inside the IDR mixing of ion populations, crescent-like velocity distributions and ion accelerations are observed. One of the spacecraft skims the outer region of the electron diffusion region, where parallel electric fields, energy dissipation/conversion, electron pressure tensor agyrotropy, electron temperature anisotropy, and electron accelerations are observed. Some of the difficulties of the observations of magnetic reconnection in turbulent plasma are also outlined.

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  • 42.
    Voros, Zoltan
    et al.
    Austrian Acad Sci, Space Res Inst, Graz, Austria; RCAES, Geodet & Geophys Inst, Sopron, Hungary.
    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.
    Narita, Yasuhito
    Austrian Acad Sci, Space Res Inst, Graz, Austria.
    MMS Observations of Whistler and Lower Hybrid Drift Waves Associated with Magnetic Reconnection in the Turbulent Magnetosheath2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402Article in journal (Refereed)
    Abstract [en]

    Magnetic reconnection (MR) and the associated concurrently occurring waves have been extensively studied at large-scale plasma boundaries, in quasi-symmetric and asymmetric configurations in the terrestrial magnetotail and at the magnetopause. Recent high-resolution observations by MMS (Magnetospheric Multiscale) spacecraft indicate that MR can occur also in the magnetosheath where the conditions are highly turbulent when the upstream shock geometry is quasi-parallel. The strong turbulent motions make the boundary conditions for evolving MR complicated. In this paper it is demonstrated that the wave observations in localized regions of MR can serve as an additional diagnostic tool reinforcing our capacity for identifying MR events in turbulent plasmas. It is shown that in a close resemblance with MR at large-scale boundaries, turbulent reconnection associated whistler waves occur at separatrix/outflow regions and at the outer boundary of the electron diffusion region, while lower hybrid drift waves are associated with density gradients during the crossing of the current sheet. The lower hybrid drift instability can make the density inhomogeneities rippled. The identification of MR associated waves in the magnetosheath represents also an important milestone for developing a better understanding of energy redistribution and dissipation in turbulent plasmas.

  • 43.
    Voros, Zoltan
    et al.
    Austrian Acad Sci, Space Res Inst, Graz, Austria;Hungarian Acad Sci, Geodet & Geophys Inst, Sopron, Hungary.
    Yordanova, Emiliya
    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.
    Varsani, Ali
    Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Narita, Yasuhito
    Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Energy Conversion at Kinetic Scales in the Turbulent Magnetosheath2019In: Frontiers in Astronomy and Space Sciences, E-ISSN 2296-987X, Vol. 6, article id 60Article in journal (Refereed)
    Abstract [en]

    The process of conversion or dissipation of energy in nearly collisionless turbulent space plasma, is yet to be fully understood. The existing models offer different energy dissipation mechanisms which are based on wave particle interactions or non-resonant stochastic heating. There are other mechanisms of irreversible processes in space. For example, turbulence generated coherent structures, e.g., current sheets are ubiquitous in the solar wind and quasi-parallel magnetosheath. Reconnecting current sheets in plasma turbulence are converting magnetic energy to kinetic and thermal energy. It is important to understand how the multiple (reconnecting) current sheets contribute to spatial distribution of turbulent dissipation. However, detailed studies of such complex structures have been possible mainly via event studies in proper coordinate systems, in which the local inflow/outflow, electric and magnetic field directions, and gradients could be studied. Here we statistically investigate different energy exchange/dissipation (EED) measures defined in local magnetic field-aligned coordinates, as well as frame-independent scalars. The presented statistical comparisons based on the unique high-resolution MMS data contribute to better understanding of the plasma heating problem in turbulent space plasmas.

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  • 44.
    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.

  • 45.
    Yordanova, Emiliya
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Perri, S.
    Sorriso-Valvo, L.
    Carbone, V.
    Multipoint observation of anisotropy and intermittency in solar-wind turbulence2015In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 110, no 1, article id 19001Article in journal (Refereed)
    Abstract [en]

    Using high-resolution magnetic-field Cluster observations, we have investigated the magnetic-field anisotropy via the second-and fourth-order structure functions over a wide range of scales reaching below the subproton scale. The magnetic-field increments have been computed from single-and two-spacecraft measurements. The two-satellite technique allows us to study the increments as a function of an actual space lag. Both single-and two-point analyses show that the magnetic field is anisotropic even at small time/spatial scales. The single-spacecraft data also shows that the degree of anisotropy does not change with the scale at proton and subproton scales. It is also pointed out that the degree of magnetic-field anisotropy tends to be overestimated in the single-spacecraft data analysis. This is particularly evident at small scales and it depends on the angle between the spacecraft separation and the flow direction. From the fourth-order moment of the probability density function of the magnetic-field increments we have also investigated the presence of intermittency in the fluctuations. Even though to a different degree, intermittency was present over the entire range of scales, with an indication of scale invariance at subproton scales.

  • 46.
    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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  • 47.
    Yordanova, Emiliya
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Voros, Z.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.;Eotvos Lorand Univ, Dept Geophys & Space Sci, Budapest, Hungary.;Hungarian Acad Sci, Geodet & Geophys Inst, RCAES, Sopron, Hungary..
    Varsani, A.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Norgren, Cecilia
    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.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Elin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Nakamura, R.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Lindqvist, P. -A
    Marklund, G.
    Royal Inst Technol, Space & Plasma Grp, Stockholm, Sweden..
    Ergun, R. E.
    Univ Colorado, Atmospher & Space Phys Lab, Campus Box 392, Boulder, CO 80309 USA..
    Magnes, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Baumjohann, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Fischer, D.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Plaschke, F.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Narita, Y.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Russell, C. T.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA..
    Strangeway, R. J.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA..
    Le Contel, O.
    Univ Paris 11, UPMC, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, Paris, France..
    Pollock, C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Torbert, R. B.
    Southwest Res Inst, San Antonio, TX USA..
    Giles, B. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Avanov, L. A.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Dorelli, J. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.;Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Paterson, W. R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Lavraud, B.
    CNRS, IRAP, Toulouse, France.;CNRS, Toulouse, France..
    Saito, Y.
    JAXA, Tokyo, Japan..
    Electron scale structures and magnetic reconnection signatures in the turbulent magnetosheath2016In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 12, p. 5969-5978Article in journal (Refereed)
    Abstract [en]

    Collisionless space plasma turbulence can generate reconnecting thin current sheets as suggested by recent results of numerical magnetohydrodynamic simulations. The Magnetospheric Multiscale (MMS) mission provides the first serious opportunity to verify whether small ion-electron-scale reconnection, generated by turbulence, resembles the reconnection events frequently observed in the magnetotail or at the magnetopause. Here we investigate field and particle observations obtained by the MMS fleet in the turbulent terrestrial magnetosheath behind quasi-parallel bow shock geometry. We observe multiple small-scale current sheets during the event and present a detailed look of one of the detected structures. The emergence of thin current sheets can lead to electron scale structures. Within these structures, we see signatures of ion demagnetization, electron jets, electron heating, and agyrotropy suggesting that MMS spacecraft observe reconnection at these scales.

  • 48.
    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;Res Ctr Astron & Earth Sci, Geodet & Geophys Inst, Sopron, Hungary.
    Raptis, Savvas
    Royal Inst Technol, Space & Plasma Phys, Stockholm, Sweden.
    Karlsson, Tomas
    Royal Inst Technol, Space & Plasma Phys, Stockholm, Sweden.
    Current Sheet Statistics in the Magnetosheath2020In: Frontiers in Astronomy and Space Sciences, E-ISSN 2296-987X, Vol. 7, article id 2Article in journal (Refereed)
    Abstract [en]

    The magnetosheath (MSH) plasma turbulence depends on the structure and properties of the bow shock (BS). Under quasi-parallel (Q(||)) and quasi-perpendicular (Q(perpendicular to)) BS configurations the electromagnetic field and plasma quantities possess quite distinct behavior, e.g., being highly variable and structured in the Q(||) case. Previous studies have reported abundance of thin current sheets (with typical scales of the order of the plasma kinetic scales) in the Q(||) MSH, associated with magnetic reconnection, plasma heating, and acceleration. Here we use multipoint observations from Magnetospheric MultiScale (MMS) mission, where for the first time a comparative study of discontinuities and current sheets in both MSH geometries at very small spacecraft separation (of the order of the ion inertial length) is performed. In Q(||) MSH the current density distribution is characterized by a heavy tail, populated by strong currents. There is high correlation between these currents and the discontinuities associated with large magnetic shears. Whilst, this seems not to be the case in Q(perpendicular to) MSH, where current sheets are virtually absent. We also investigate the effect of the discontinuities on the scaling of electromagnetic fluctuations in the MHD range and in the beginning of the kinetic range. There are two (one) orders of magnitude higher power in the magnetic (electric) field fluctuations in the Q(||) MSH, as well as different spectral scaling, in comparison to the Q(perpendicular to) MSH configuration. This is an indication that the incoming solar wind turbulence is completely locally reorganized behind Q(perpendicular to) BS while even though modified by Q(||) BS geometry, the downstream turbulence properties are still reminiscent to the ones upstream, the latter confirming previous observations. We show also that the two geometries are associated with different temperature anisotropies, plasma beta, and compressibility, where the Q(perpendicular to) MSH is unstable to mostly mirror mode plasma instability, while the Q(||) MSH is unstable also to oblique and parallel fire-hose, and ion-cyclotron instabilities.

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  • 49.
    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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