Storm time production of ring current ions: Variations in particle energization and injection with ionospheric source region

Abstract

Using single‐particle tracking with time‐dependent global magnetic and electric fields from multifluid simulations, we model the 10 March 1998 storm and investigate storm time acceleration, injection, and trapping mechanisms associated with the formation of the ring current. We examine the contribution from various ionospheric source regions to the storm time ring current and the effect interplanetary magnetic field Bz has on producing an asymmetric and symmetric ring current; we provide the first maps for the relative importance of ionospheric outflow (H+ and O+) regions as a function of all magnetic local times (MLTs) and latitudes between 60° and 80°. During the early part of the storm, high‐latitude outflow regions between 00 and 06 MLT are the most efficient sectors at contributing particle density to the ring current, whereas during the main phase of the storm, there is more even contribution from all MLTs. The sectors that contribute the majority of the energy are consistently the high‐latitude regions between 03 and 09 MLT. An increase in the contribution of O+ to the current density is observed from the predawn high‐latitude region during each of two decreases in Dst examined for the 10 March 1998 storm, supporting the central role oxygen plays in storm development. Asymmetries are observed between H+ and O+ contributions. The dominant ionospheric species contributing to the ring current energy density is shown to vary during the course of the storm with a significant increase in ionospheric O+ contribution to the ring current associated with large decreases in Dst.