Effect of dust absorption on the electron avalanche process occurring within Martian dust storms

Abstract

Martian dust devils and storms are believed to generate and maintain large-scale E-fields which may be strong enough to create a weakly ionized plasma in the low pressure CO2 atmosphere. Previous studies of the electron development included a determination of the avalanching electron growth via electron impact ionization with CO2 at electron energy levels above 14 eV Townsend's first coefficient defining the path length for impact ionization was calculated as a function of driving electric field. Such calculations demonstrated the growth of the electron avalanche but did not include any electron loss processes. Herein, we consider the effect of such a loss process: electron absorption by dust grains. The inclusion of electron-dust absorption has a moderating effect, controlling electron avalanche growth. A critical E-field to initiate the avalanche is derivable, with fields below ∼7 kV/m quenching the process but above 7 kV/m fully capable of stimulating electron growth in the storm.