Date of Award

Fall 2010

Document Type

Thesis - Open Access

Degree Name

Master of Science in Engineering Physics

Department

Physical Sciences

Committee Chair

Katariina Nykyri

Committee Member

John M. Hughes

Committee Member

Mark Anthony Reynolds

Abstract

The high-altitude magnetospheric cusps are regions of significant magnetic field turbulence. There are also magnetic field fluctuations that cannot be called turbulence. Some of the low frequency fluctuations observed in the cusp have been shown to be motion of the cusp structure by the spacecraft (back and forth motion of the boundaries surrounding the cusp); others are transient reconnection signatures or flux transfer events (FTEs). Turbulence is important to understand because it has been proposed as a mechanism for particle energization in the cusps to MeV levels. High resolution magnetic field data from the Fluxgate Magnetometer instruments on the Cluster satellites were used to statistically map the power of the magnetic field fluctuations in the frequency ranges of 0.017-10 Hz, 0.017-0.1 Hz, and 0.1-10 Hz for the high-altitude cusp and surrounding boundaries for northward, southward, and all interplanetary magnetic field clock angle orientations by using three years of Cluster data, 118 northern hemisphere cusp crossings, from 2001-2003. The mean (compressive), total, and perpendicular (transverse) power were calculated. Analysis was done to check whether the locations of enhanced power were statistically consistent with the locations of crossing of cusp boundaries and diamagnetic cavities. Sources of power in all frequency ranges studied, 0.017-10 Hz, include reconnection, a gradient in the magnetic field strength when moving from the magnetosphere to the magnetosheath, and possibly the earthward propagation of magnetotail reconnection fluctuations. Sources of wave power from 0.017-0.1 Hz include mirror mode, ion-cyclotron, and Alfven waves. Sources of wave power from 0.1-10 Hz include ion-cyclotron and Alfven waves.

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