Role of the Inductive Electric Field to the Ring Current Particle Energization and Trapping

The dynamic nature of magnetic field within inner magnetosphere region plays an important role in the transport and energization process of ring current ion species, by altering the local gradient-curvature drift of trapped ring current ion population, changing the bounce path length of trapped particles, and inducing a global inductive electric field, as described by Faraday's law, that accelerates particles within a short period of time. Quantifying the effect brought by the dynamic nature of magnetic field is crucial for providing a realistic and accurate description of the dynamic and time-evolution of terrestrial ring current, especially during storm time, when the dynamic nature of magnetic field is prominent.

The motions of different particle population trapped within inner magnetosphere are both energy and pitch-angle dependent, so standard single fluid treatment of plasma cannot provide adequate description of the inner magnetosphere. To accurately simulate this closed field lines region, a kinetic model solving the energy and pitch-angle dependent particle drift of hot ions and electrons is needed. The Hot Electron Ion Drift Integrator (HEIDI) kinetic model is able to separate the contribution from different aspects of the dynamic nature of magnetic field, to particle drift, energization rate and pitch-angle scattering. We present here, for the first time, an assessment of the role the inductive electric field plays in trapping particles in the inner magnetosphere, and in the intensification of the ring current.

Comparison results on the drift, energization rate and pitch-angle change obtained from HEIDI, by both coupling it with BATS-R-US and running stand alone, have been obtained to analyze the effect of different aspects of time-changing magnetic field on the ring-current ion dynamics. In coupled mode, BATS-R-US provides HEIDI with self-consistent electric (separated by source) and magnetic field information, while in stand-alone mode, HEIDI itself is able to calculate a self-consistent inductive electric field generated by a time varying analytic stretching dipole magnetic field.