Monte Carlo simulation of photoelectron energization in parallel electric fields: electroglow on Uranus

Abstract

A Monte Carlo simulation of photoelectron energization and energy degradation in H₂ gas in the presence of parallel electric fields has been carried out. Numerical yield spectra which contain information about the electron energy degradation process and can be used to calculate the yield for any inelastic event are obtained. The variation of yield spectra with incident electron energy, electric field, pitch angle, and cutoff limit has been studied. The yield function is employed to determine the photoelectron fluxes. H₂ Lyman and Werner band excitation rates and integrated column intensity are computed for three different electric field profiles taking various low-energy cutoff limits. It is found that an electric field profile with peak value of 4 mV/m at neutral number density of 3×10¹⁰ cm^-3 produces enhanced volume emission rates of H₂ bands [λ < 1100 Å] explaining about 20% of the observed electroglow emission on Uranus. The effect of solar zenith angle and solar cycle variation on peak excitation rate is discussed.