Abstract/Details

Electric fields and current sheet structure in magnetospheric plasmas


2007 2007

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Abstract (summary)

The electric currents of the central plasma sheet play a pivotal role in the dynamics of the Earth’s magnetosphere. I describe new instrumentation developed for measuring its properties, and analyze data from existing instruments. The analysis shows the structure and physical current-carrying mechanisms of the quiescent central plasma sheet in new detail.

Electric field observations are critical for this work. I discuss two aspects of space-based double-probe electric field experiments: the probe design and the signal processing. I develop a numerical model that self-consistently solves for the interaction between the probes and the nearby plasma environment, including the effects of the spacecraft and its attendant photoelectrons. I also describe the signal processing hardware developed for the 5-satellite THEMIS mission, known as the Digital Fields Boards (DFB). THEMIS was launched in February 2007, and all 5 DFBs are working as intended.

Since THEMIS is only recently launched, I analyze data from the 4-satellite Cluster mission, which has similar instrumentation. With Cluster data, the position of the current sheet relative to the satellite can be determined, allowing direct comparisons between observations and models. To encompass the wide variety of possible current-carrying mechanisms, I develop a kinetic model based on the quasi-isotropic formalism of Schindler and Birn [2002]. The model fits many of the observed sheets well.

The observations reveal a wide variety of current-carrying mechanisms. Some of the thinnest currents consist entirely of a pair of electron Hall currents which together form a bifurcated current sheet driven by strong inward-pointing electric fields.

Indexing (details)


Subject
Astronomy;
Atmospheric sciences;
Plasma physics
Classification
0606: Astronomy
0725: Atmospheric sciences
0759: Plasma physics
Identifier / keyword
Pure sciences; Earth sciences; Current sheets; Electric fields; Kinetic model; Magnetosphere; Magnetospheric plasmas
Title
Electric fields and current sheet structure in magnetospheric plasmas
Author
Cully, C. M.
Number of pages
244
Publication year
2007
Degree date
2007
School code
0051
Source
DAI-B 70/02, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9781109040685
Advisor
Ergun, Robert
University/institution
University of Colorado at Boulder
Department
Astrophysical and Planetary Sciences
University location
United States -- Colorado
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3344778
ProQuest document ID
304889514
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/304889514
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