Insights into the solar wind conditions near Mars from data science techniques

Durward, Sofija and Wild, Jim (2023) Insights into the solar wind conditions near Mars from data science techniques. PhD thesis, Lancaster University.

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Abstract

Mars’ plasma environment is strongly driven by its interaction with the solar wind, however the lack of an upstream solar wind monitor at Mars sometimes necessitates assumptions about the variability of solar wind and interplanetary magnetic field (IMF) conditions. This thesis investigates the variability in the solar wind. The first study finds the IMF to be notably steadier in field strength, clock angle and cone angle direction during the Mars Global Surveyor (MGS) mission than the Mars Atmosphere and Volatile Evolution (MAVEN) mission. Additionally, the variability of the field strength, clock angle and cone angle were all found to be dependant on the cone angle of the measurements, with periods of IMF oriented close to the ecliptic plane being considerably steadier than periods of IMF oriented approximately perpendicular to it. The second study presents a data-driven model to predict the upstream solar wind conditions for periods where MAVEN was inside the martian magnetosphere. The predictions of this model are compared with those from a solar wind propagation model commonly used at Mars, and the model presented in this thesis was found to better capture the velocity of the solar wind during periods of more variable solar wind. The final study of this thesis investigates orientation preferences in the interplanetary magnetic field using clustering techniques to group IMF measurements by field strength and stability of the cone angle. It finds that periods of low strength and steady orientation are typically aligned in one of two orientations which correspond to ‘towards’ and ‘away’ sectors of the IMF. During periods of higher field strength, the cone angles are constrained out of the ecliptic plane.