Trapped Population Response During Geomagnetic Auroral Super Storms

The radiation belts have a more pronounced response to global disturbances of the magnetospheric
system during geomagnetic super storms. Those are characterized as prolonged periods of high
magnetic activity and identified by several indices, such as the Dst index. The magnetospheric
current system is enhanced during storms and causes consequential variations in the Earth’s
magnetic field, thus producing a surface electric field. We study two super storms, on August 2000
and April 2001 for which the distribution of the helium ion (He+) population in the plasmasphere
defined as the torus of cold dense plasma surrounding the Earth in the inner magnetosphere is
imaged using the extreme ultraviolet (EUV) instrument on board the NASA-IMAGE spacecraft. We
aim to analyze the variation of the He+ density in the plasmasphere during those storms and we
search for enhancements in the He+ density budget. We determine the plasmapause location and
map it to ionospheric altitude along the magnetic field lines. The ionospheric context is then studied
in terms of auroral precipitation using FUV imaging of the electron and proton aurora at higher
latitude. The electric field is also considered using measurements of the ionospheric convection
from the SuperDARN radar network and using DMSP crossings of that region.