Dynamics of ring current and electric fields in the inner magnetosphere during disturbed periods: CRCM–BATS‐R‐US coupled model

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Abstract
We present simulation results from a one‐way coupled global MHD model (Block‐Adaptive‐Tree Solar‐Wind Roe‐Type Upwind Scheme, BATS‐R‐US) and kinetic ring current models (Comprehensive Ring Current Model, CRCM, and Fok Ring Current, FokRC). The BATS‐R‐US provides the CRCM/FokRC with magnetic field information and plasma density/temperature at the polar CRCM/FokRC boundary. The CRCM uses an electric potential from the BATS‐R‐US ionospheric solver at the polar CRCM boundary in order to calculate the electric field pattern consistent with the CRCM pressure distribution. The FokRC electric field potential is taken from BATS‐R‐US ionospheric solver everywhere in the modeled region, and the effect of Region II currents is neglected. We show that for an idealized case with southward‐northward‐southward Bz IMF turning, CRCM–BATS‐R‐US reproduces well known features of inner magnetosphere electrodynamics: strong/weak convection under the southward/northward Bz; electric field shielding/overshielding/penetration effects; an injection during the substorm development; Subauroral Ion Drift or Polarization Jet (SAID/PJ) signature in the dusk sector. Furthermore, we find for the idealized case that SAID/PJ forms during the substorm growth phase, and that substorm injection has its own structure of field‐aligned currents which resembles a substorm current wedge. For an actual event (12 August 2000 storm), we calculate ENA emissions and compare with Imager for Magnetopause‐to‐Aurora Global Exploration/High Energy Neutral Atom data. The CRCM–BATS‐R‐US reproduces both the global morphology of ring current and the fine structure of ring current injection. The FokRC‐BATS‐R‐US shows the effect of a realistic description of Region II currents in ring current–MHD coupled models.

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