Auroral Particle Acceleration at Jupiter

Lorch, Chris and Ray, Licia and Arridge, Chris and O'Keeffe, Helen (2022) Auroral Particle Acceleration at Jupiter. PhD thesis, Lancaster University.

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Abstract

Plasmas naturally occur in our solar system in the form of the Sun, the solar wind, and material within the magnetospheres and ionospheres of planets and satellites. Today, space exploration provides access to ideal natural laboratories, such as Jupiter’s unique magnetospheric environment, which provide insights into plasma physics largely irreproducible on Earth. This thesis begins by outlining fundamental physical concepts needed to understand planetary magnetospheres, before diving into the more subtle and complex details which distinguish Jupiter’s magnetosphere from Earth’s. The mechanisms resulting in the Jovian magnetosphere-ionospheric coupled system are explained, followed by comparisons of plasma turbulence in Jupiter’s, Earth’s, and Sun’s magnetic environments. This is followed by an overview of the various spacecraft which have visited Jupiter and the instruments that are utilised in this thesis. Chapter 5 presents work published in Lorch et al. (2020), which investigates equatorial asymmetries in the magnetosphere-ionosphere current system, expanding on previous work with extended magnetic field datasets, new model integration and automated magnetic field signature identification processes. Previously unquantified height integrated current densities are calculated, and areas where field aligned current topology is equally determined by both radial and azimuthal current divergence are highlighted. Chapter 6 explores drivers of auroral particle acceleration within the mid-to-high latitude regions of Jupiter’s magnetosphere. Lorch et al. (2022) used state-of-the-art Juno magnetometer and plasma data to identify a series of Alfvénic turbulence events which display an energy dissipative spectral index at scales approaching the electron inertial length, which potentially feed energy into wave-particle acceleration mechanisms capable of producing the observed auroral energy flux. This thesis concludes with a project roadmap aiming to quantify MHD and Alfvénic turbulence within all spatial regions of Jupiter’s magnetosphere. This work was initiated but did not reach completion due to the onset of the COVID-19 pandemic.