Empirical modeling of the storm-time innermost magnetosphere using Van Allen Probes and THEMIS data: Eastward and banana currents

TitleEmpirical modeling of the storm-time innermost magnetosphere using Van Allen Probes and THEMIS data: Eastward and banana currents
Publication TypeJournal Article
Year of Publication2015
AuthorsStephens, GK, Sitnov, MI, Ukhorskiy, AY, Roelof, EC, Tsyganenko, NA, Le, G
JournalJournal of Geophysical Research: Space Physics
Paginationn/a - n/a
Date Published01/2015
Keywordseastward current; empirical geomagnetic field; magnetic storm; ring current; Van Allen Probes
AbstractThe structure of storm-time currents in the inner magnetosphere, including its innermost region inside 4RE, is studied for the first time using a modification of the empirical geomagnetic field model TS07D and new data from Van Allen Probes and THEMIS missions. It is shown that the model, which uses basis-function expansions instead of ad hoc current modules to approximate the magnetic field, consistently improves its resolution and magnetic field reconstruction with the increase of the number of basis functions and resolves the spatial structure and evolution of the innermost eastward current. This includes a connection between the westward ring current flowing largely at inline image and the eastward ring current concentrated at inline image resulting in a vortex current pattern. A similar pattern coined ‘banana current’ was previously inferred from the pressure distributions based on the energetic neutral atom imaging and first-principles ring current simulations. The morphology of the equatorial currents is dependent on storm phase. During the main phase, it is complex, with several asymmetries forming 'banana currents'. Near Sym-H minimum, the 'banana current' is strongest, is localized in the evening-midnight sector, and is more structured compared to the main phase. It then weakens during the recovery phase resulting in the equatorial currents to become mostly azimuthally symmetric.
URLhttp://doi.wiley.com/10.1002/2015JA021700
DOI10.1002/2015JA021700
Short TitleJ. Geophys. Res. Space Physics


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