Magnetic Reconnection in the Collisional Ionosphere of Mars

Ion loss from the topside ionosphere of Mars associated with the solar wind interaction makes an important contribution to the loss of volatiles from this planet. Data from NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission combined with theoretical modeling are helping us to understand the processes controlling the Martian ionosphere and its interaction with the solar wind. Magnetic reconnection is a key topic in space plasma physics and operates in the solar corona, at planetary magnetospheres, and in astrophysical plasmas. For the most part, reconnection is considered to take place in collision-less plasmas. However, at Mars the reconnection should often take place in regions where collisions are important. Mars does not have a large-scale global magnetic field. However, Mars has locally large magnetic fields due to remnant crustal magnetization, particularly in the highland regions of the southern hemisphere. The crustal fields provide a "target' for reconnection both in the dayside ionosphere of Mars and in the magnetotail. The reconnection is associated with topological changes in the field and is also a source of energy for the plasma, thus affecting the ionospheric dynamics and ion loss from the planet. Both theoretical concepts and MAVEN particle and field data from several instruments will be discussed.