E. Gordeev

The substorm cycle as reproduced by global MHD models

Recently Gordeev et al. [2015] suggested a method to test global MHD models against statistical empirical data. They showed that four community-available global MHD models supported by the Community Coordinated Modeling Center (CCMC) produce a reasonable agreement with reality for those key parameters (the magnetospheric size, magnetic field and pressure) that are directly related to the large-scale equilibria in the outer magnetosphere. Based on the same set of simulation runs, here we investigate how the models reproduce the global loading-unloading cycle. We found that in terms of global magnetic flux transport, three examined CCMC models display systematically different response to idealized 2h north then 2h south IMFBz variation. The LFM model shows a depressed return convection and high loading rate during the growth phase as well as enhanced return convection and high unloading rate during the expansion phase, with the amount of loaded/unloaded magnetotail flux and the growth phase duration being the closest to their observed empirical values during isolated substorms. Two other models exhibit drastically different behavior. In the BATS-R-US model the plasma sheet convection shows a smooth transition to the steady convection regime after the IMF southward turning. In the Open GGCM a weak plasma sheet convection has comparable intensities during both the growth phase and the following slow unloading phase. We also demonstrate potential technical problem in the publicly-available simulations which is related to post-processing interpolation and could affect the accuracy of magnetic field tracing and of other related procedures.

Magnetotail magnetic flux monitoring based on simultaneous solar wind and magnetotail observations

This work was supported by Russian Science Foundation grant 14-17-00072. The CLUSTER-based tail magnetic flux computation for years 2001–2009 was supported by FP7 ECLAT project, they are now available via CSA. We are grateful to all teams for the opportunity to use their observational data. We thank NASA CDAWeb (http://cdaweb.gsfc.nasa.gov/istp_public/) for IMF, solar wind, and magnetic index data; the AMPERE project (http://ampere.jhuapl.edu) for AMPERE data; the THEMIS website (http://themis.ssl.berkeley.edu/) for THEMIS spacecraft data, Cluster Science Archive (http://www.cosmos.esa.int/web/csa) for Cluster data; the IMAGE-FUV data were supplied by the NASA Space Science Data Centre(NSSDC). The global MHD simulations were made possible due to NASA Community Coordinated Modeling Center effort (http://ccmc.gsfc.nasa.gov/). S.E.M. was supported by the Science and Technology Facilities Council (STFC), UK, grant ST/K001000/1. The work at the Birkeland Centre for Space Centre, University of Bergen, Norway, was supported by the Research Council of Norway/CoE under contract 223252/F50. We also thank Stepan Dubyagin for help in calculating THEMIS total pressure, Peter Boakes for data on magnetotail plasma domains, and Marianna Kholeva for help with the manuscript preparation.