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  • 1.
    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 applications, ISSN 1542-7390, 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.

  • 2.
    Facsko, G.
    et al.
    Hungarian Acad Sci, Res Ctr Astron & Earth Sci, Geodet & Geophys Inst, Sopron, Hungary.;Finnish Meteorol Inst, FIN-00101 Helsinki, Finland..
    Honkonen, I.
    Finnish Meteorol Inst, FIN-00101 Helsinki, Finland.;NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Zivkovic, T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. DNV GL, Res & Innovat, Hovik, Norway..
    Palin, Laurianne
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Kallio, E.
    Aalto Univ, Sch Elect Engn, Espoo, Finland..
    Ågren, K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Opgenoorth, Hermann
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Tanskanen, E. I.
    Aalto Univ, ReSoLVE Ctr Excellence, ELEC Dept Radio Sci & Engn, Espoo, Finland..
    Milan, S.
    Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England..
    One year in the Earth's magnetosphere: A global MHD simulation and spacecraft measurements2016In: Space Weather: The international journal of research and applications, ISSN 1542-7390, E-ISSN 1542-7390, Vol. 14, no 5, p. 351-367Article in journal (Refereed)
    Abstract [en]

    The response of the Earth's magnetosphere to changing solar wind conditions is studied with a 3-D Magnetohydrodynamic (MHD) model. One full year (155 Cluster orbits) of the Earth's magnetosphere is simulated using Grand Unified Magnetosphere Ionosphere Coupling simulation (GUMICS-4) magnetohydrodynamic code. Real solar wind measurements are given to the code as input to create the longest lasting global magnetohydrodynamics simulation to date. The applicability of the results of the simulation depends critically on the input parameters used in the model. Therefore, the validity and the variance of the OMNIWeb data are first investigated thoroughly using Cluster measurement close to the bow shock. The OMNIWeb and the Cluster data were found to correlate very well before the bow shock. The solar wind magnetic field and plasma parameters are not changed significantly from the L-1 Lagrange point to the foreshock; therefore, the OMNIWeb data are appropriate input to the GUMICS-4. The Cluster SC3 footprints are determined by magnetic field mapping from the simulation results and the Tsyganenko (T96) model in order to compare two methods. The determined footprints are in rather good agreement with the T96. However, it was found that the footprints agree better in the Northern Hemisphere than the Southern one during quiet conditions. If the B-y is not zero, the agreement of the GUMICS-4 and T96 footprint is worse in longitude in the Southern Hemisphere. Overall, the study implies that a 3-D MHD model can increase our insight of the response of the magnetosphere to solar wind conditions.

  • 3.
    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 applications, ISSN 1542-7390, 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.

  • 4.
    Liemohn, Michael W.
    et al.
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI USA.
    McCollough, James P.
    US Air Force, Space Vehicles Directorate, Res Lab, Kirtland AFB, NM USA.
    Jordanova, Vania K.
    Los Alamos Natl Lab, Space Sci & Applicat, Los Alamos, NM USA.
    Ngwira, Chigomezyo M.
    Catholic Univ Amer, Dept Phys, Washington, DC USA; NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Morley, Steven K.
    Los Alamos Natl Lab, Space Sci & Applicat, Los Alamos, NM USA.
    Cid, Consuelo
    Univ Alcala De Henares, Dept Phys & Math, Madrid, Spain.
    Tobiska, W. Kent
    Space Environm Technol, Pacific Palisades, CA USA.
    Wintoft, Peter
    Swedish Inst Space Phys, Lund, Sweden.
    Ganushkina, Natalia Yu
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI USA; Finnish Meteorol Inst, Helsinki, Finland.
    Welling, Daniel T.
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI USA; Univ Texas Arlington, Arlington, TX USA.
    Bingham, Suzy
    UK Met Off, Exeter, Devon, England.
    Balikhin, Michael A.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England.
    Opgenoorth, Hermann
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Engel, Miles A.
    Los Alamos Natl Lab, Space Sci & Applicat, Los Alamos, NM USA.
    Weigel, Robert S.
    George Mason Univ, Dept Phys & Astron, Fairfax, VA USA.
    Singer, Howard J.
    NOAA, Space Weather Predict Ctr, Boulder, CO USA.
    Buresova, Dalia
    CAS, Inst Atmospher Phys, Prague, Czech Republic.
    Bruinsma, Sean
    Dept Space Geodesy CNES, Toulouse, France.
    Zhelayskaya, Irina S.
    GFZ German Res Ctr Geosci, Potsdam, Germany; Univ Potsdam, Inst Phys & Astron, Potsdam, Germany.
    Shprits, Yuri Y.
    GFZ German Res Ctr Geosci, Potsdam, Germany; Univ Potsdam, Inst Phys & Astron, Potsdam, Germany; UCLA, Dept Earth & Space Sci, Los Angeles, CA USA.
    Vasile, Ruggero
    GFZ German Res Ctr Geosci, Potsdam, Germany.
    Model Evaluation Guidelines for Geomagnetic Index Predictions2018In: Space Weather: The international journal of research and applications, ISSN 1542-7390, E-ISSN 1542-7390, Vol. 16, no 12, p. 2079-2102Article in journal (Refereed)
    Abstract [en]

    Geomagnetic indices are convenient quantities that distill the complicated physics of some region or aspect of near‐Earth space into a single parameter. Most of the best‐known indices are calculated from ground‐based magnetometer data sets, such as Dst, SYM‐H, Kp, AE, AL, and PC. Many models have been created that predict the values of these indices, often using solar wind measurements upstream from Earth as the input variables to the calculation. This document reviews the current state of models that predict geomagnetic indices and the methods used to assess their ability to reproduce the target index time series. These existing methods are synthesized into a baseline collection of metrics for benchmarking a new or updated geomagnetic index prediction model. These methods fall into two categories: (1) fit performance metrics such as root‐mean‐square error and mean absolute error that are applied to a time series comparison of model output and observations and (2) event detection performance metrics such as Heidke Skill Score and probability of detection that are derived from a contingency table that compares model and observation values exceeding (or not) a threshold value. A few examples of codes being used with this set of metrics are presented, and other aspects of metrics assessment best practices, limitations, and uncertainties are discussed, including several caveats to consider when using geomagnetic indices.

  • 5.
    Mann, I. R.
    et al.
    Univ Alberta, Dept Phys, Edmonton, AB, Canada.
    Di Pippo, S.
    United Nations Off Vienna, Off Outer Space Affairs, Vienna, Austria.
    Opgenoorth, Hermann Josef
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Univ Leicester, Dept Phys & Astron, Leicester, Leics, England.
    Kuznetsova, M.
    NASA, Goddard Spaceflight Ctr, Greenbelt, MD USA.
    Kendall, D. J.
    Canadian Space Agcy, St Hubert, PQ, Canada.
    International Collaboration Within the United Nations Committee on the Peaceful Uses of Outer Space: Framework for International Space Weather Services (2018-2030)2018In: Space Weather: The international journal of research and applications, ISSN 1542-7390, E-ISSN 1542-7390, Vol. 16, no 5, p. 428-433Article in journal (Other academic)
    Abstract [en]

    Severe space weather is a global threat that requires a coordinated global response. In this Commentary, we review some previous successful actions supporting international coordination between member states in the United Nations (UN) context and make recommendations for a future approach. Member states of the UN Committee on the Peaceful Uses of Outer Space (COPUOS) recently approved new guidelines related to space weather under actions for the long-term sustainability of outer space activities. This is to be followed by UN Conference on the Exploration and Peaceful Uses of Outer Space (UNISPACE)+50, which will take place in June 2018 on the occasion of the fiftieth anniversary of the first UNISPACE I held in Vienna in 1968. Expanded international coordination has been proposed within COPUOS under the UNISPACE+50 process, where priorities for 2018-2030 are to be defined under Thematic Priority 4: Framework for International Space Weather Services. The COPUOS expert group for space weather has proposed the creation of a new International Coordination Group for Space Weather be implemented as part of this thematic priority. This coordination group would lead international coordination between member states and across international stakeholders, monitor progress against implementation of guidelines and best practices, and promote coordinated global efforts in the space weather ecosystem spanning observations, research, modeling, and validation, with the goal of improved space weather services. We argue that such improved coordination at the international policy level is essential for increasing global resiliency against the threats arising from severe space weather.

  • 6.
    Welling, D. T.
    et al.
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI USA; Univ Texas Arlington, Dept Phys, Arlington, TX USA.
    Ngwira, C. M.
    Catholic Univ Amer, Dept Phys, Washington, DC USA; NASA, Goddard Space Flight Ctr, Space Weather Lab, Greenbelt, MD USA.
    Opgenoorth, Hermann
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Univ Leicester, Dept Phys & Astron, Leicester, Leics, England.
    Haiducek, J. D.
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI USA.
    Savani, N. P.
    NASA, Goddard Space Flight Ctr, Space Weather Lab, Greenbelt, MD USA; Univ Maryland Baltimore Cty, Goddard Planetary Heliophys Inst, Baltimore, MD USA.
    Morley, S. K.
    Los Alamos Natl Lab, Space Sci & Applicat, Los Alamos, NM USA.
    Cid, C.
    Univ Alcala De Henares, Space Weather Res Grp, Alcala De Henares, Spain.
    Weigel, R. S.
    George Mason Univ, Dept Phys & Astron, Space Weather Lab, Fairfax, VA USA.
    Weygand, J. M.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA.
    Woodroffe, J. R.
    Los Alamos Natl Lab, Space Sci & Applicat, Los Alamos, NM USA.
    Singer, H. J.
    NOAA, Space Weather Predict Ctr, Boulder, CO USA.
    Rosenqvist, L.
    Swedish Def Res Agcy, Stockholm, Sweden.
    Liemohn, M. W.
    Univ Michigan, Dept Climate & Space Sci & Engn, Ann Arbor, MI USA.
    Recommendations for Next-Generation Ground Magnetic Perturbation Validation2018In: Space Weather: The international journal of research and applications, ISSN 1542-7390, E-ISSN 1542-7390, Vol. 16, no 12, p. 1912-1920Article in journal (Refereed)
    Abstract [en]

    Data-model validation of ground magnetic perturbation forecasts, specifically of the time rate of change of surface magnetic field, dB/dt, is a critical task for model development and for mitigation of geomagnetically induced current effects. While a current, community-accepted standard for dB/dt validation exists (Pulkkinen et al., 2013), it has several limitations that prevent more complete understanding of model capability. This work presents recommendations from the International Forum for Space Weather Capabilities Assessment Ground Magnetic Perturbation Working Team for creating a next-generation validation suite. Four recommendations are made to address the existing suite: greatly expand the number of ground observatories used, expand the number of events included in the suite from six to eight, generate metrics as a function of magnetic local time, and generate metrics as a function of activity type. For each of these, implementation details are explored. Limitations and future considerations are also discussed.

  • 7.
    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 applications, ISSN 1542-7390, 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.

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