The current system in the Earth's magnetosphere plays an essential role in the transport of mass and energy in the space (Davenport, 1996;Olson, 1984). The basic structure and dynamics of the primary electric current systems (e.g., magnetopause current, magnetotail current, ring current, and field-aligned current) determine the coupling between different regions of the magnetosphere (Ganushkina et al., 2018). The ring current flowing around the Earth is one of the most important space currents in the inner magnetosphere and is usually referred as the westward ring current since the ions drift westward and electrons drift eastward. During geomagnetic storms, the ring current exhibits a significant asymmetry at different magnetic local times (MLTs), mainly manifested by the dawn-dusk asymmetry (

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.