Simulating the Ion Precipitation from the Inner Magnetosphere by H-band
and He-band Electro Magnetic Ion Cyclotron (EMIC) Waves
Abstract
During geomagnetic storms, magnetospheric wave activity drives the ion
precipitation which can become an important source of energy flux into
the ionosphere and strongly affect the dynamics of the
Magnetosphere-Ionosphere (MI) coupling. In this study, we investigate
the role of Electro Magnetic Ion Cyclotron (EMIC) waves in causing ion
precipitation into the ionosphere using simulations from the RAM-SCBE
model with and without EMIC waves included. The global distribution of
H-band and He-band EMIC wave intensity in the model is based on three
different EMIC wave models statistically derived from satellite
measurements. Comparisons among the simulations and with observations
suggest that the EMIC wave model based on recent Van Allen Probes
observations is the best in reproducing the realistic ion precipitation
into the ionosphere. Specifically, the maximum precipitating proton
fluxes appear at L=4-5 in the afternoon-to-night sector which is in good
agreement with statistical results, and the temporal evolution of
integrated proton energy fluxes at auroral latitudes is consistent with
earlier studies of the stormtime precipitating proton energy fluxes and
vary in close relation to the Dst index. Besides, the simulations with
this wave model can account for the enhanced precipitation of
<20 keV proton energy fluxes at regions closer to earth
(L<5) as measured by NOAA/POES satellites, and reproduce
reasonably well the intensity of <30 keV proton energy fluxes
measured by DMSP satellites. It is suggested that the inclusion of
H-band EMIC waves improves the intensity of precipitation in the model
leading to better agreement with the NOAA/POES data.