The Martian Ionosphere in Regions of Crustal Magnetic Fields
Withers, Mendillo, and Hinson

The magnetic field of Mars varies significantly over horizontal scales of hundreds of kilometers, unlike the smoother dipole field of the Earth. Its complicated topology is more extreme than any other planetary magnetic field in the solar system. Magnetic fields can affect ionospheres in several ways. Firstly, they can modify the influx of energetic particles from the solar wind. Secondly, they can modify the direction of ion transport by diffusion. Thirdly, they can modify the direction of bulk plasma transport due to winds and electric fields. Mars Global Surveyor's Radio Science Experiment has measured over 2000 profiles of electron density of which 220 occur in the southern hemisphere. We have identified very large changes in electron density over short vertical distances in about 30 of these 2000 profiles. These 30 profiles were all measured over the crustal magnetic anomalies in the southern hemisphere. We will show some examples of these unusual profiles and discuss causative mechanisms.