The Local and Global Effects of Magnetic Reconnection at Mars

The nature of the solar wind-planetary interaction depends on the properties of the solar wind, such as the interplanetary magnetic field (IMF), as well as the intrinsic magnetism and/or ionospheric properties of the planet. The volume of space that bounds this interaction region defines a planet's magnetosphere. The plasma environment around Mars behaves as a hybrid magnetosphere that exhibits characteristics of both induced and intrinsic magnetospheric processes. This hybrid nature is the result of strong crustal magnetic anomalies at Mars that are unequally distributed across the surface of the planet. These anomalies form "mini-magnetospheres" that interact with the solar wind. Magnetic reconnection is a ubiquitous space plasma physics phenomenon that reassigns magnetic field lines to new arrangements and mixes and energizes previously separated plasma populations. In this work, we analyze the local and global effects of magnetic reconnection via in situ orbital observations made by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Our results demonstrate that: (1) magnetic reconnection between the crustal anomalies and the IMF is the main driver for the formation of bundles of twisted magnetic flux known as magnetic flux ropes. We compiled a database of magnetic flux rope observations made by MAVEN and concluded that 91% were likely formed via magnetic reconnection. Flux rope formation illustrates examples of mini-magnetospheric processes occurring at Mars. (2) Magnetic reconnection also plays a role in discrete aurora formation within two mini-magnetospheres. We demonstrate that 87% of discrete aurora observations detected by the Imaging Ultraviolet Spectrograph onboard MAVEN occurred when the local IMF and underlying mini-magnetospheres are oriented in a way that favors magnetic reconnection. This work explains previously reported trends in discrete aurora detections and lays a framework for understanding Martian discrete aurora from a mini-magnetospheric point of view. (3) Our global analysis of the distribution of crustal anomalies at Mars measured by MAVEN has revealed that magnetic reconnection between the crustal fields and the IMF is favored when the IMF points southward. This result holds a variety of interesting implications regarding global measurements of magnetic connectivity at Mars. This work demonstrates that magnetic reconnection at Mars produces byproducts we also observe at planets with global intrinsic magnetic fields such as flux ropes, and aurora, as well as organizes large-scale plasma phenomena at Mars. The importance of magnetic reconnection within the Martian magnetosphere highlights its hybrid nature and underlines the limitless variety of solar wind-magnetosphere interactions that are possible both within our solar system and beyond.PhDClimate and Space Sciences and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/176609/1/bowersch_1.pd