By using the magnetic field data from of Van Allen Probes, we analyzed
the distribution characteristics of the electromagnetic environment in
the inner magnetosphere on different Dst* index and magnetic local time
(MLT). Our results show that for the response of different current
systems, the dawn-dusk and noon-midnight asymmetry distribution of the
residual magnetic field δB increases with Dst* index. When Dst*
< -60 nT, a ‘banana’-shaped geomagnetic field negative
disturbance peak region appears in the sector from midnight to dusk.
Then, we obtained the azimuthal current density and found the asymmetric
internal eastward and external westward ring current. Through the vector
analysis of three-dimensional current density, the current density
vector distribution in the magnetic equatorial plane (MEP) is completely
displayed for the first time, which directly proves the existence of
banana current near r = 3.0 - 4.0 RE during strong geomagnetic storms.