The effects of inductive electric field on the spatial and temporal
evolution of inner magnetospheric ring current
Abstract
Charged particles are observed to be injected into the inner
magnetosphere region from plasma sheet, and energized up to high
energies over short distance and time, during both geomagnetic storms
and substorms. Numerous studies suggest that it is the short-duration
and high-speed plasma flows, which are closely associated with the
global effects of magnetic reconnection and inductive effects, rather
than the slow and steady convection that control the Earth-ward plasma
transport and magnetic flux from the magnetotail, especially during
geomagnetic activities. In order to include the effect of inductive
electric produced by the temporal change of magnetic field on the
dynamics of ring current, we implemented both theoretical and numerical
modifications to an inner magnetosphere kinetic model—Hot Electron-Ion
Drift Integrator (HEIDI). New drift terms associated with the inductive
electric field are incorporated into the calculation of bounce-averaged
coefficients for the distribution function, and their numerical
implementations and the associated effects on total drift and
energization rate are discussed. Numerical simulations show that the
local particle drifts are significantly altered by the presence of
inductive electric fields, in addition to the changing magnetic
gradient-curvature drift due to the distortion of magnetic field, and at
certain locations, the inductive drift dominates both the potential and
the magnetic gradient-curvature drift. The presence of a self consistent
inductive electric field alters the overall particle trajectories,
energization, and pitch angle, resulting in significant changes in the
topology and strength of the ring current.