Multi-spacecraft observations of chorus dispersion and source location
by Breneman, Aaron Winfield, Ph.D., THE UNIVERSITY OF IOWA, 2008, 75 pages; 3323401

Abstract:

We report the source locations and emission characteristics of 62 chorus events identified with a ray tracing technique. Chorus waves have a characteristic frequency/time slope on a spectrogram that is a combination of frequency separation by propagation dispersion and a time variation of emission frequency. A cross-correlation technique comparing data from multiple Cluster spacecraft quantifies the frequency separation due to propagation dispersion. The comparison of the data cross-correlations with the simulated cross-correlations allows the identification of the source region. Any remaining frequency/time slope in the single spacecraft spectrograms not accounted for by the cross-correlations is then used to determine the time variation of emission frequency. The final source region and time variation of emission frequency for each individual chorus event are consistent with both the cross-correlation and single spacecraft data for that event. The 62 chorus source regions are located near the magnetic equator and are, in general, more extended parallel to the Earth's magnetic field than perpendicular to it. Histograms of wave normal and group velocity angles emitted by the aggregate of simulated sources are presented. It is found that waves in both the upper and lower band of chorus are emitted in a broad spectrum of wave normal angles with some preference for the Gendrin angle in the lower band. All waves, however, propagate along the Earth's magnetic field with little variation. Finally, the time variation of emission frequency for these events ranges from 1–20 kHz/sec. For most events these rates account for at least 2/3 of the chorus frequency/time slope with the rest being due to propagation dispersion.

 
AdviserCraig A. Kletzing
SchoolTHE UNIVERSITY OF IOWA
SourceDAI/B 69-07, p. , Oct 2008
Source TypeDissertation
SubjectsAstronomy; Nuclear physics
Publication Number3323401
Adobe PDF Access the complete dissertation:
 

» Find an electronic copy at your library.
  Use the link below to access a full citation record of this graduate work:
  http://gateway.proquest.com/openurl%3furl_ver=Z39.88-2004%26res_dat=xri:pqdiss%26rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation%26rft_dat=xri:pqdiss:3323401
  If your library subscribes to the ProQuest Dissertations & Theses (PQDT) database, you may be entitled to a free electronic version of this graduate work. If not, you will have the option to purchase one, and access a 24 page preview for free (if available).

About ProQuest Dissertations & Theses
With over 2.3 million records, the ProQuest Dissertations & Theses (PQDT) database is the most comprehensive collection of dissertations and theses in the world. It is the database of record for graduate research.

The database includes citations of graduate works ranging from the first U.S. dissertation, accepted in 1861, to those accepted as recently as last semester. Of the 2.3 million graduate works included in the database, ProQuest offers more than 1.9 million in full text formats. Of those, over 860,000 are available in PDF format. More than 60,000 dissertations and theses are added to the database each year.

If you have questions, please feel free to visit the ProQuest Web site - http://www.proquest.com - or call ProQuest Hotline Customer Support at 1-800-521-3042.