Ion Instrumentation for Space Physics Applications & Pickup Dynamics at Quasi-Perpendicular Shocks

Date
2021
Authors
Starkey, Michael Joseph
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Abstract

As the field of heliophysics evolves, improvements in space plasma measurement methods and instrumentation are needed in order to address emerging theories. The first part of this dissertation focuses on ion instrumentation for space physics applications. First, the characterization of avalanche photo-diodes (APDs) response times when measuring suprathermal ions is discussed. Next, the results of the calibration of the Suprathermal Ion Sensor (SIS) that will fly on the CuSP mission is reported. The results of these works will aid in the implementation and interpretation of space-based measurements of suprathermal ion populations. In the second part of this dissertation, the dynamics of He+ pickup ions at quasi-perpendicular shocks are investigated using data from the Magnetospheric MultiScale (MMS) mission. Chapters 4 and 5 discuss work in which a nearly perpendicular and quasi-perpendicular shock, respectively, was analyzed for signs of preferentially energized He+, relative to the local magnetic field. The final chapter of this dissertation discusses 10 observations of quasi-perpendicular shocks made by MMS. In the analyses of these shock events, integrated He+ velocity distribution functions were compared upstream and downstream of the shock and relative to the local magnetic field. 1D distribution functions were computed in the parallel and perpendicular directions, which were then used to identify signs of preferential heating and energization in the perpendicular direction as a function of the fast magnetosonic Mach number, Mf. These results reveal that He+ PUIs are energized preferentially in the direction magnetic to the field at quasi-perpendicular shocks, and that this energization is stronger for shocks with higher Mf. Taken together, the results of this dissertation help to improve future instrumentation for space plasma applications and will aid in the interpretation and analysis of in-situ plasma measurements. Furthermore, these results help to advance the field of ion acceleration at shocks and can aid in future modelling efforts of pickup ion dynamics at shocks throughout the heliosphere.

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Keywords
Avalanche photodiode, Collisionless shocks, ion acceleration, pickup ions, plasma instrumentation
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Department
Physics and Astronomy