Date of Award

2017

Access Type

Dissertation - Open Access

Degree Name

Doctor of Philosophy in Engineering Physics

Department

Physical Sciences

Committee Chair

Dr. Katariina Nykyri, Ph.D

First Committee Member

Dr. Anatoly Streltsov, Ph.D

Second Committee Member

Dr. Matthew Zettergren, Ph.D

Third Committee Member

Dr. Jay Johnson, Ph.D

Abstract

In the Earth’s magnetosphere, the magnetotail plasma sheet ions are much hotter than in the shocked solar wind. On the dawn-sector, the cold-component ions are more abundant and hotter by 30-40 percent when compared to the dusk sector. Recent statistical studies of the flank magnetopause and magnetosheath have shown that the level of temperature asymmetry of the magnetosheath is unable to account for this (Dimmock et al., 2015), so additional physical mechanisms must be at play, either at the magnetopause or plasma sheet, that contribute to this asymmetry. This thesis focuses on ion heating across the magnetopause boundary separating the magnetosheath and the magnetospheric plasmas, which is driven by mechanisms operating on fluid, ion and electron scales. One of the pending problems in collisionless astrophysical plasmas is to understand the plasma heating and transport across three fundamental scales: fluid, ion and electron. Presented here is evidence of the energy transport between the fluid and ion scales: energy is provided by a velocity shear at the magnetopause generating fluid-scale Kelvin-Helmholtz Instability and their rolled-up vortices, where an ion-scale fast magnetosonic wave packet located in the center of a Kelvin-Helmholtz vortex has sufficient energy to account for observed cold-component ion heating. In addition, a statistical analysis is performed on the ion-scale wave properties in the three main plasma regimes common to flank magnetopause boundary crossings when the boundary is unstable to KHI: hot and tenuous magnetospheric, cold and dense magnetosheath and mixed (H. Hasegawa, Fujimoto, Phan, et al., 2004). The statistical analysis shows that during KH events there is enhanced non-adiabatic heating calculated during ion scale wave intervals when compared to non-KH events. This suggests that during KH events there is more free energy for ion-scale wave generation, which in turn can heat ions more effectively when compared to cases when KH waves are absent. This may contribute to the dawn favored temperature asymmetry of the plasma sheet, because KH waves are statistically more abundant on the dawn sector. Furthermore, the present findings have universal consequences in understanding cross-scale energy transport from fluid to ion-scales, applicable to a variety of environments experiencing velocity shears with comparable plasma regimes.

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