Modeling photoelectron transport in the Martian ionosphere at Olympus Mons and Syrtis Major: MGS observations

Abstract

We have calculated photoelectron flux, ion production rates, and electron densities in the Martian ionosphere close to Syrtis Major and Olympus Mons at coordinates 5°N, 30°E and 15°N, 210°E, respectively. In the regions of Olympus Mons and Syrtis Major the magnetic fields are horizontal and vertical, respectively. These calculations are made at solar zenith angle 78° during moderate solar activity using transport and local loss models of photoelectrons based on the yield spectrum method. The vertical transport of photoelectrons is inhibited by horizontal magnetic fields at Olympus Mons. In this case we have used a local loss calculation. Photoelectron transport is allowed in the vertical magnetic fields at Syrtis Major. In this case we have developed and applied a photoelectron transport model. The estimated ion production rates are then used in a one‐dimensional continuity and vertical diffusion model to calculate ion and electron density. It is found that photoelectron transport reduces the flux by an order of magnitude between energy range 1 to 20 eV at higher altitude (>250 km). In this region the production rates and densities are decreased by factors of 2.5 to 5 due to transport of photoelectrons.