[Previous] | [Session 10] | [Next]
J. G. Luhmann (Space Sciences Lab, U of California Berkeley)
Though small in scale, Mercury's magnetosphere is substantial enough to temporarily capture passing energetic interplanetary electrons accelerated in flares or corotating interaction regions, or from the Jovian magnetosphere. To investigate the extent to which flux buildup can occur, a numerical experiment is conducted in which a model Hermean magnetosphere is exposed to electrons of different energies at its magnetopause, and the electrons' behavior is tracked. Though not permanently trapped because of the small size of the magnetosphere relative to Mercury, electrons can be temporarily contained for times well beyond their nominal interplanetary passage times under certain conditions determined by entry location and interplanetary field behavior. The Mercury magnetosphere model used for this study is a scaled version of the Tsyganenko T96-01 terrestrial magnetosphere model, which has been found to provide a good approximation to the observations from Mariner 10. Approximately isotropic energetic (500 keV-50 MeV) energetic electron distributions are initialized at the magnetopause, after which the particles are followed until they either impact the planet, exit the system, or travel the maximum allowed number of time steps. At these high energies, their motion is not significantly affected by magnetospheric convection electric fields, which are not modeled. The current model also does not take into account other possibly important factors such as scattering of the electrons by waves in the magnetosphere, or deflections of their trajectories by magnetosheath fields or the still unknown higher order moments of the Hermean magnetic field, all of which should discourage trapping. These results may nevertheless be of interest to those considering space weather effects on the Hermean atmosphere, or the low altitude radiation environment for future orbiters.