Computer Science
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001phdt.........4k&link_type=abstract
Thesis (PhD). UNIVERSITY OF MINNESOTA, Source DAI-B 62/06, p. 2648, Dec 2001, 117 pages.
Computer Science
Scientific paper
The phenomenon of the aurora is effected by the dynamics of the magnetotail. The dominant region in the magnetotail is the plasma sheet. An understanding of the electrodynamics of the plasma sheet is thus crucial for an understanding of the aurora. The work presented in this thesis comprises an investigation of the electrodynamics of the plasma sheet and its poleward boundary at distances of 4-7 RE using the Polar satellite. The results presented herein have increased our knowledge about the relationship between the processes in the plasma sheet and auroral phenomena. Measurement from the Polar satellite provide evidence for large electric field structures in the region under investigation. These structures have amplitudes perpendicular to the ambient magnetic field and the nominal plasma sheet that can exceed 100 mV/m. In a large database statistical study, covering two years of satellite operation, we investigated the properties of these electric field structures. The results shed further light on the spatial distribution, occurrence frequency, and mapping characteristic of perpendicular electric fields on auroral field lines. In addition, individual events were studied in greater detail with regard to their origin, which led to the identification of Alfvén waves in the plasma sheet boundary layer. Furthermore, the coupling between the plasma sheet region under investigation and the ionosphere was investigated from an energetic point of view. Evidence is provided that Poynting flux carried by Alfvén waves on auroral field lines at 4-7 RE geocentric distance is correlated with the energy flux of magnetically conjugate precipitating electrons at 100 km altitude. The Poynting flux exceeded the energy flux necessary to power the conjugate auroras, suggesting that the Poynting flux supplies the energy for low-altitude acceleration processes. In a conjugate study with ground stations it is also shown that the largest in-situ Poynting fluxes occurred during the expansion phase of substorms. These observations demonstrate the importance of Alfvén wave power as a means of energy transport from the distant magnetotail to the acceleration region during magnetospheric substorms. We also demonstrated that the PSBL plays a very important role as a region that carries this energy.
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