Global MHD modeling of resonant ULF waves: Simulations with and without a plasmasphere.
We investigate the plasmaspheric influence on the resonant mode coupling of magnetospheric ultralow frequency (ULF) waves using the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic (MHD) model. We present results from two different versions of the model, both driven by the same solar wind conditions: one version that contains a plasmasphere (the LFM coupled to the Rice Convection Model, where the Gallagher plasmasphere model is also included) and another that does not (the stand-alone LFM). We find that the inclusion of a cold, dense plasmasphere has a significant impact on the nature of the simulated ULF waves. For example, the inclusion of a plasmasphere leads to a deeper (more earthward) penetration of the compressional (azimuthal) electric field fluctuations, due to a shift in the location of the wave turning points. Consequently, the locations where the compressional electric field oscillations resonantly couple their energy into local toroidal mode field line resonances also shift earthward. We also find, in both simulations, that higher-frequency compressional (azimuthal) electric field oscillations penetrate deeper than lower frequency oscillations. In addition, the compressional wave mode structure in the simulations is consistent with a radial standing wave oscillation pattern, characteristic of a resonant waveguide. The incorporation of a plasmasphere into the LFM global MHD model represents an advance in the state of the art in regard to ULF wave modeling with such simulations. We offer a brief discussion of the implications for radiation belt modeling techniques that use the electric and magnetic field outputs from global MHD simulations to drive particle dynamics.
Space Sciences Department Aerospace Corporation El Segundo California USA.
S G
SG
Claudepierre
Physics and Astronomy Department Rice University Houston Texas USA.
F R
FR
Toffoletto
High Altitude Observatory National Center for Atmospheric Research Boulder Colorado USA.
M
M
Wiltberger
field line resonance; global MHD simulation; plasmasphere; radiation belts; resonant ULF wave coupling; waveguide
Science. 2013 Aug 30;341(6149):991-4
23887876
Nature. 2013 Dec 19;504(7480):411-4
24352287
J Geophys Res Space Phys. 2016 Jan;121(1):227-244
27668142
J Geophys Res Space Phys. 2016 Aug;121(8):7895-7899
27867798