Radar Soundings of the Ionosphere of Mars

Abstract

We report the first radar soundings of the ionosphere of Mars with the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument on board the orbiting Mars Express spacecraft. Several types of ionospheric echoes are observed, ranging from vertical echoes caused by specular reflection from the horizontally stratified ionosphere to a wide variety of oblique and diffuse echoes. The oblique echoes are believed to arise mainly from ionospheric structures associated with the complex crustal magnetic fields of Mars. Echoes at the electron plasma frequency and the cyclotron period also provide measurements of the local electron density and magnetic field strength.

Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) after nine years of operation: A summary

“…include results from remote sounding, local electron density, and local magnetic field measurements. The possibilities of MARSIS AIS are summarized by Gurnett et al (2005) and by Gurnett et al (2008).…”

“…This quantity has, through the history of MARSIS, been collected manually with the aid of a cursor-driven adjustable scale on the computer monitor used to display an ionogram; however, automated methods of taking these data have now been developed and will soon supercede the manual method (see Andrews et al, 2013). The process of getting local electron density from the plasma frequency harmonics is discussed by Gurnett et al (2005), Gurnett et al (2008), Duru et al (2008), Morgan et al (2008), and Morgan et al (2013a). The origin of the plasma frequency harmonics as an artefact of feedback from the sounding pulse that is then clipped in the pre-amp -receiver complex, is discussed in the last named reference.…”

“…3 were first explained by Gurnett et al (2005) and Gurnett et al (2008). Statistical results from these data were given by Akalin et al (2010).…”

“…The MARSIS AIS electron cyclotron echoes and the extraction of the magnetic field strength was first discussed by Gurnett et al (2005) and again by Gurnett et al (2008). The electron echoes and the resulting magnetic field strengths were first used en masse by Akalin et al (2010) to map the field strength as a function of altitude and solar zenith angle.…”

Non‐detection of impulsive radio signals from lightning in Martian dust storms using the radar receiver on the Mars Express spacecraft

“…The echo intensities obtained during each frequency sweep are displayed on a color-coded plot of delay time, Dt, versus the transmitter frequency, f. This plot is called an ionogram (see Figure 1). The horizontal trace labeled "surface reflection" is the radar echo from the surface of Mars, and the two traces labeled "ionospheric echo" and "oblique ionospheric echo" are echoes from the ionosphere [see Gurnett et al, 2005]. The strong signals along the left side of the ionogram, and in a narrow horizontal band along the top of the ionogram, are decaying electrostatic disturbances excited in the plasma during the transmitted pulse.…”