Magnetic Field Variation Effects on Electron Distributions at Mars: Comparisons of Theory and Data

The Electron Reflectometer (ER) onboard the Mars Global Surveyor (MGS) satellite is intended to remotely probe the magnetic field of the planet. By measuring the velocity space distribution of fast electrons (10 eV < E < 20 keV), the spatial and temporal variability of the magnetic field topology far from the satellite can be deduced. In this presentation, results from a multi-stream kinetic calculation of fast electrons in the Mars ionosphere are compared against MGS/ER data. The influence of a non-uniform magnetic field in the electron transport simulation results is discussed, showing that pitch angle anisoptropies in the data can be explained by this effect. Data from the first few months of the mapping phase are examined to compare the similarities and differences between nearly-identical flights over the crustal field regions. This analysis yields information about the variability of the loop structures in the ionosphere, and comparison against modeling results quantifies the magnitude of the topology changes.