Meteor impact perturbation in the lower ionosphere of Mars: MGS observations

摘要

We have analyzed 1500 electron density profiles obtained from radio occultation experiment onboard Mars Global Surveyor to study the physical characteristics of meteoric plasma layers over Mars during the months of January-June, 2005. It is found that 65 electron density profiles were strongly perturbed with peak densities ～0.5-1.4 × 10~(10)m~(-3) at altitude between 80 km and 105 km probably due to ablation of meteoroids and subsequent ionization of meteoric atoms. These profiles are used to estimate Total Electron Content (TEC) in the lower atmosphere of Mars. Our analysis suggests that meteoroids ablation caused enhancements in TEC by a factor of ～1.5-3.0. We also report that maximum TEC were observed on 21 January and 23 May, 2005, when comets 2007 PL42 and 4015 Wilson-Harrington intersected the orbit of Mars from a close distance 1.49 AU and 1.17 AU, respectively. TEC were increased by a factor of ～5-7 on these days. This is a significant increase in TEC, which might be associated with the meteor showers that were produced when Mars crossed the dust stream left along the orbit of these comets.