Kinetic model of the inner magnetosphere with arbitrary magnetic field

Abstract

Theoretical and numerical modifications to an inner magnetosphere modelHot Electron Ion Drift Integrator (HEIDI)were implemented, in order to accommodate for a nondipolar arbitrary magnetic field. While the dipolar solution for the geomagnetic field during quiet times represents a reasonable assumption in the near-Earth closed field region, during storm activity this assumption becomes invalid. HEIDI solves the time-dependent, gyration- and bounce-averaged kinetic equation for the phase space density of one or more ring current species. New equations are derived for the bounce-averaged coefficients for the distribution function, and their numerical implementation is discussed. Also, numerically solving all the bounce-averaged coefficients for the dipole case does not change the results significantly from the analytical approximation of Ejiri (1978). However, distorting the magnetic field changes all bounce-averaged coefficients that make up the kinetic equation. Initial simulations show that changing the magnetic field changes the whole topology of the ring current. This is because the drifts are altered due to dayside compression and nightside stretching of the field. Therefore, at certain locations, the nondipolar magnetic drifts can dominate the convective drifts, considerably altering the pressure distribution in the equatorial plane. Copyright 2012 by the American Geophysical Union.