Global MHD simulations of plasmaspheric plumes

Abstract:

The plasmasphere represents a separate population from the rest of the
magnetosphere, generally high density but cold. When the solar wind
turns strongly southward this plasma is convected toward the dayside
magnetopause and affects the interaction of the solar wind with the
magnetosphere. We have used multi-fluid simulations using the LFM
global MHD code to model this interaction. The plasmasphere is
initialized as a cold (~1eV) hydrogen plasma in a quiet northward IMF
state with a density distribution appropriate for K_p = 1. The
corotation potential from the ionosphere spins up the plasmasphere
into rough corotation. After a initialization period of hours, a
southward IMF is introduced and the enhanced convection initiates a
surge of plasmaspheric density to the dayside. We discuss two aspects
of this interaction, the effects on dayside reconnection and on the
Kelvin-Helmholtz instability (KHI). We find that the mass loading of
magnetospheric flux tubes slows local reconnection rates, though not
as much as predicted by Borovsky et al. [2013]. We find
that the total reconnection rate is reduced, although not as much as
would be predicted by just the sub-solar reconnection rate. The KHI
is somewhat reduced by the plasmaspheric loading of density in the low
latitude boundary layer. It has been suggested that the presence of
the plasmasphere may lead to enhanced ULF wave power in the interior
of the magnetosphere from the KHI waves. We find only a minimal effect during northward IMF. For southward IMF, the situation is complicated by the interaction of KHI with non-steady reconnection.