Spatiotemporal Studies of the Martian Plasma Environment

This thesis studies the spatiotemporal variability of phenomena within the Martian plasma environment arising from the interaction of the interplanetary solar environment with the Martian upper atmosphere and ionosphere. In particular, two phenomena have been studied including, (1) rapid reductions in the superthermal electron plasma population, or ‘electron holes’, within the illuminated Martian induced magnetosphere (IM), and (2) the outermost interface of the Martian plasma environment to the solar wind, the Martian bow shock. I have used ~ 11 years (2004 to 2015) of plasma observations at Mars by the Mars Express (MEX) mission to investigate aspects of these phenomena that no previous study has been able to explore. Bespoke automated algorithms have been devised to identify both the electron holes and the Martian bow shock over this time period. I have identified that the electron holes are a common occurrence within the illuminated Martian IM, with 56% of the MEX orbits over the period containing at least one event. I have verified that the spatial distribution of these phenomena are colocated with the intense crustal magnetic fields, and demonstrated that their altitudinal distribution is dependent on the relative intensity of the crustal magnetic fields. Using the long timescale MEX bow shock observations, I have computed statistically robust models of the Martian bow shock shape and location, and consequently studied its spatial variability over time. For the first time, I have demonstrated that average bow shock position varies by 10% throughout Mars’ elliptical orbit of the Sun. I have used complimentary datasets to describe this variation in terms of the solar wind dynamic pressure, EUV flux, and the crustal magnetic fields. This newfound knowledge has then allowed me to discover that the Martian bow shock’s average altitude varies by 5 - 10% over the period of the ~ 11 year solar cycle.