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THREE-DIMENSIONAL EXOSPHERIC HYDROGEN ATOM DISTRIBUTIONS
OBTAINED FROM OBSERVATIONS OF THE GEOCORONA IN LYMAN-ALPHA
by
Justin J. Bailey
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(ASTRONAUTICAL ENGINEERING)
May 2012
Copyright 2012 Justin J. Bailey
Object Description
| Title | Three-dimensional exospheric hydrogen atom distributions obtained from observations of the geocorona in Lyman-alpha |
| Author | Bailey, Justin J. |
| Author email | jjbailey@usc.edu;justin.j.bailey@alumni.usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Astronautical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2012-02-28 |
| Date submitted | 2012-04-24 |
| Date approved | 2012-04-24 |
| Restricted until | 2012-04-24 |
| Date published | 2012-04-24 |
| Advisor (committee chair) | Gruntman, Mike |
| Advisor (committee member) |
Erwin, Dan Kunc, Joseph Tobiska, Kent Judge, Darrell |
| Abstract | Exospheric atomic hydrogen (H) resonantly scatters solar Lyman-alpha (121.567 nm) radiation, observed as the glow of the geocorona. Measurements of scattered solar photons allow one to probe time-varying three-dimensional distributions of exospheric H atoms. The Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) mission images the magnetosphere in energetic neutral atom (ENA) fluxes and additionally carries Lyman-alpha Detectors (LADs) to register line-of-sight intensities of the geocorona. This work details a process for preparing TWINS data such that LAD measurements can be used to obtain global H density distributions with three-dimensional asymmetries above 3 earth radii. Sequences of distributions are presented to investigate the dynamic exosphere, responding to seasonal variations between a summer solstice and autumnal equinox, as well as to solar and geomagnetic variations as described by commonly used indices. The distributions reveal asymmetries from day to night, north to south, and dawn to dusk. A nightside extension persists that is consistent with the location of a geotail. A seasonal north-south asymmetry occurs as solar illumination differs between the summer and winter polar regions. Pole-equator and less pronounced dawn-dusk asymmetries also appear, possibly due to a coupling effect via charge exchange with the polar wind and plasmasphere, respectively. ❧ A common phenomenon in geospace occurs as magnetospheric energetic ions collide with neutral background atoms and produce ENAs that, no longer bound by Earth's magnetic field, can travel large distances though space with minimal disturbance — providing an opportunity for remote detection. Knowledge of the distribution of the primary neutral partner, exospheric H atoms, is therefore essential for the interpretation of ENA fluxes and subsequent retrieval of ion densities. An analysis is summarized that demonstrates the importance of exospheric H density distributions on reconstructing magnetospheric images in ENA fluxes and obtaining ring current ion densities. ❧ Some of the main findings in this work have been accepted [Ilie et al., 2012] or are already published [Bailey and Gruntman, 2011; Zoennchen et al., 2011] in various scientific journals. |
| Keyword | alpha; atomic; exosphere; geocorona; hydrogen; Lyman |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m |
| Rights | Bailey, Justin J. |
| Access conditions | The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given. |
| Repository name | University of Southern California Digital Library |
| Repository address | USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA |
| Repository email | cisadmin@usc.edu |
| Archival file | uscthesesreloadpub_Volume4/etd-BaileyJust-629-0.pdf |
Description
| Title | Page 1 |
| Full text | THREE-DIMENSIONAL EXOSPHERIC HYDROGEN ATOM DISTRIBUTIONS OBTAINED FROM OBSERVATIONS OF THE GEOCORONA IN LYMAN-ALPHA by Justin J. Bailey A Dissertation Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (ASTRONAUTICAL ENGINEERING) May 2012 Copyright 2012 Justin J. Bailey |
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