Plasma Sources and Evolution in the Global Magnetosphere and Wave Generation in the Outer Magnetosphere

Date
2017
Authors
Allen, Robert C.
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Abstract

The magnetosphere of Earth is the region of space in which the geomagnetic field dominates. At the outer boundary of the magnetosphere, plasma and fields that originate from the sun, which dominate interplanetary space, interact with the magnetosphere. Through pressure balance, magnetic reconnection, and various instabilities, the interplay between interplanetary space and the magnetosphere can drive a variety of dynamics that have consequences for modern technology and human spaceflight. This dissertation focuses on two of such dynamics: (1) the sources and evolution of plasma within the magnetosphere and (2) electromagnetic ion cyclotron (EMIC) waves generated in the outer magnetosphere.

Understanding the sources and subsequent evolution of plasma in a magnetosphere holds intrinsic importance for magnetospheric dynamics. Plasma populations in the Earth's magnetosphere can originate from one of two sources: the ionosphere, characterized by a low charge states (e.g., O+), and the solar wind, characterized by higher charge states (e.g., O 6+). We present here a detailed analysis of ionosphere-originating O+ and solar wind-originating O6+ distributions, correlating these populations to different injection mechanisms into and dynamics within the magnetosphere.

EMIC waves act as an energy transport mechanism within the magnetosphere. Regions of hot anisotropic ions can set off the EMIC instability, which will then propagate along the magnetic field away from the source region, before resonating with ion populations elsewhere. This study investigates the generation of EMIC waves in the outer magnetosphere and finds that the compression of the dayside magnetosphere, due to solar wind bombardment, leads to off-equator EMIC generation.

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Keywords
Magnetosphere, Plasma Sources, Plasma Waves, Solar Wind
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Department
Physics and Astronomy