Magnetic tilt effect on externally driven electromagnetic ion cyclotron
(EMIC) waves
Abstract
We examine the wave coupling efficiency of solar wind to magnetospheric
fluctuations in the ULF frequency range using an advanced full-wave
simulation code, Petra-M. Earth’s magnetic field is tilted to the
ecliptic plane; thus, compressional wave sources can be incident over a
wide range of magnetic latitudes. When compressional waves are incident
at a low latitude, very little wave power can reach the inner
magnetosphere. On the other hand, waves incident from a high latitude
source can propagate efficiently into the inner magnetosphere and reach
the ground near the cusp region. The mode-conversion and polarization
reversal at the crossover plays a critical role in compressional wave
propagation. The mode-converted linearly polarized electromagnetic ion
cyclotron waves also occur at the Alfvén and ion-ion hybrid resonances.
Therefore, the results suggest that solar wind compression can drive the
linearly polarized EMIC waves, and the wave occurrence can have seasonal
and diurnal dependence.