Magnetic Reconnection In The Ionosphere Of Mars: The Role Of Collisions

This paper evaluates the role of magnetic reconnection in the dayside ionosphere of Mars in the collisional regime and presents some relevant data from the MAVEN (Mars Atmosphere and Volatile EvolutioN) mission. Magnetic reconnection is an important process operating in the solar corona, planetary magnetospheres, and astrophysical plasmas, but most of the literature focuses on collisionless plasmas. However, at Mars the reconnection should often occur in regions where collisions are important. Mars does not have a large-scale global magnetic field; however, Mars has locally large magnetic fields associated with remnant crustal magnetization, particularly in the highland regions of the southern hemisphere. The crustal fields provide a "target" for reconnection both in the ionosphere and in the magnetotail of Mars. The current paper emphasizes the dayside ionosphere. Magnetic reconnection is associated with topological changes in the magnetic field and is also a source of energy for the plasma and can thus affect the ionospheric dynamics and ion loss at Mars. Both theoretical concepts and MAVEN particle and field data from several instruments are considered in this paper.Plain Language Summary Magnetic reconnection is an important physical process in solar system and astrophysical plasmas (i.e., magnetized charged particle gases). During this process, the topology of the field lines is generally altered. For example, two sets of field lines-one connected at both ends to the Sun (i.e., interplanetary field lines advected into the ionosphere by the solar wind flow) and a second set connecting at both ends to the interior of Mars, "reconnect" in the relatively small "diffusion region." The resulting field lines reach from the Sun into the surface of Mars (i.e., "open" field lines). Energy stored in the magnetic field is released during the reconnection process, thus providing kinetic energy to the electrons and ions in the plasma. The purpose of this paper is to explore some theoretical ideas of how collisions could affect magnetic reconnection in the Martian ionosphere and then to present one observational example using MAVEN (Mars Atmosphere and Volatile EvolutioN) data.