Radio atmospheric propagation on Mars and potential remote sensing applications

We theoretically analyze the propagation of very low frequency (VLF) and extremely low frequency (ELF) electromagnetic energy in the spherical waveguide formed by the ground and ionosphere of Mars to investigate the possibility of using such signals to remotely sense Martian ground conductivity and ionospheric parameters. This energy is presumed to be radiated from an electrical discharge in a Martian dust storm. Using a synthesis of observed and modeled Martian ionospheric and ground parameters and assuming a discharge current similar to that in a terrestrial lightning discharge, we calculate radio atmospheric spectra and waveforms for a variety of discharge orientations and observed electromagnetic field components. A number of characteristics of the modeled Martian radio atmospherics (sferics) are found to be significantly different from those of terrestrial sferics, and we discuss how these features could provide information regarding the Martian ionosphere. We also show that measurements of VLF and ELF attenuation rates could provide a measurement of large-scale ground conductivity to a depth of a few kilometers or more, thereby providing a technique for probing large-scale subsurface geological features which affect bulk conductivity, such as areas containing ice or water.