Empirical modeling of the storm time innermost magnetosphere using Van Allen Probes and THEMIS data: Eastward and banana currents. Issue 1 (6th January 2016)

• Record Type: Journal Article
• Authors: Stephens, G. K.; Sitnov, M. I.; Ukhorskiy, A. Y.; Roelof, E. C.; Tsyganenko, N. A.; Le, G.
• Is Part Of: Journal of geophysical research. Volume 121:Issue 1(2016:Jan.)
• Page Start: 157
• Page End: 170
• Publication Date: 2016-01-06
• Subjects: empirical geomagnetic field -- ring current -- eastward current -- magnetic storm; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2015JA021700
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: The structure of storm time currents in the inner magnetosphere, including its innermost region inside 4 R E, is studied for the first time using a modification of the empirical geomagnetic field model TS07D and new data from Van Allen Probes and Time History of Events and Macroscale Interactions during Substorms 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 R ≳ 3 R E and the eastward ring current concentrated at R ≲ 3 R E 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. Key Points: TS07D model increases resolution given more data and basis functions Magnetic field data inside 4 R E improves the empirical picture New version of TS07D resolves eastward and banana currents