Photoelectron flux and nightglow emissions of 5577 and 6300 Å due to solar wind electron precipitation in Martian atmosphere

Abstract

The detailed model calculations of photoelectron flux and nightglow emissions of 5577 and 6300 Å lines are made using analytical yield spectrum approach based on Monte Carlo method. The calculated photoelectron spectra are compared with electron reflectometer (ER) measurements made by Mars Global Surveyor (MGS) at the energy range 10-1000 eV. This calculation suggests that X-ray ionization is an important process in the dayside ionosphere of Mars at energy greater than 90 eV, and 10- to 90-eV electron population is controlled by photoionization and photoelectron impact ionization. The secondary electron flux, excitation rates, emission rates, and limb intensities of 5577 and 6300 Å lines are calculated due to precipitation of solar wind electrons observed by ER experiment at the energy range 10-1000 eV in the nighttime ionosphere of Mars. In the vicinity of the peak altitudes, it is found that excitation/emission of atomic oxygen after the electron impact dissociation of CO2 is the main source of 5577 Å emissions, while dissociative recombination of molecular oxygen ion is the major source of 6300 Å emissions after the electron impact excitation of atomic oxygen. The calculated secondary electron spectra are also compared with ER experiment measurements between energies of 10 and 1000 eV. The nightglow limb intensities are compared with the upper limit set by Mars 5 spectroscopic observations.