Conditions at the Magnetopauses of Jupiter and Saturn and Implications for the Solar Wind Interaction

Meier, Mariel

Graduate Thesis Or Dissertation

Conditions at the Magnetopauses of Jupiter and Saturn and Implications for the Solar Wind Interaction Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/h702q641c

Abstract

The nature of the solar wind interaction with the giant outer planets, Jupiter and Saturn, has not been well described or understood, due to limited measurements of the plasma conditions and magnetic fields at the magnetopauses of these planets. At Earth this interaction can be examined in depth with local spacecraft and measurements from the planet's surface. It is accepted that large-scale reconnection between the draped interplanetary magnetic field and planetary magnetic field is the dominant method by which the solar wind imparts mass and momentum to the terrestrial magnetosphere. When reconnection is suppressed, due to a parallel magnetic field configuration, viscous processes at the magnetopause mediate the interaction. At the outer planets, the environments in which this interaction takes place differ significantly from the terrestrial case, due to the changes in the solar wind with radial distance, along with the larger sizes of the magnetospheres and internal plasma sources at the moons Io and Enceladus. Using idealized models of the magnetosheath and magnetosphere magnetic fields, plasma densities, and plasma flow, I test for the steady state viability of processes mediating the interaction between the solar wind and the jovian and kronian magnetospheres. The magnetopauses are modeled as asymmetric paraboloids with variable asymmetry. I test where on the magnetopause surface large-scale reconnection may be affected by either a shear flow or diamagnetic drift due to a pressure gradient across the magnetopause boundary. I also test for the onset of the Kelvin-Helmholtz instability. I find that while the onset of reconnection is highly sensitive to changes in solar wind and magnetosphere conditions at both planets, the Kelvin-Helmholtz instability on the dawn flanks of these magnetopauses is active independent of changes in these conditions. I use a hybrid code simulation to explore how changes in solar wind and magnetosphere conditions affect the growth rate of the Kelvin-Helmholtz instability as well as transportation of mass and momentum across the magnetopause boundary.

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