Source region characteristics of magnetospheric ELF/VLF banded chorus emissions
Abstract/Contents
- Abstract
- Geomagnetically trapped electrons with relativistic energies in the Earth's radiation belts may cause serious damage to spacecraft systems through their interactions with onboard electronics. Natural electromagnetic plasma waves, known as extremely low frequency/very low frequency (ELF/VLF) chorus, can increase the flux of relativistic electrons by accelerating electrons with energies in the keV range to energies in the MeV range. Chorus, observed in the magnetosphere outside the plasmapause, often appears in two distinct frequency bands separated by an emission gap, which occurs where the wave power exhibits a minimum. This configuration, known as banded chorus, consists of an upper band (UB) of chorus located above the emission gap and a lower band (LB) of chorus located below this gap. This dissertation explores the source region characteristics of magnetospheric banded chorus emissions using data from the Cluster spacecraft and the Polar spacecraft to advance our fundamental understanding of the properties of these waves. A new theory suggests that the emission gap between the upper and lower bands of chorus is due to ducting effects. To test this theory, plasmaspheric electron densities with the highest spatial resolution to date are determined for accurate identification of whistler-mode ducts. Wave normal angle distributions near the magnetic equator demonstrate that banded chorus can be generated within, and likely guided by, enhancement and depletion ducts and that lower band chorus emissions can be uniformly excited over an extended region. Further analysis of the wave normal angle distributions in the equatorial and off-equatorial regions shows lower band chorus tends to be quasi-field-aligned and upper band chorus tends to have oblique wave normal angles. Finally, the intensity of banded chorus is determined to have an exponential spatial dependence on distance away from the magnetic equator, providing a new boundary condition for chorus generation models.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2012 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Haque, Naoshin |
|---|---|
| Associated with | Stanford University, Department of Electrical Engineering |
| Primary advisor | Inan, Umran S |
| Thesis advisor | Inan, Umran S |
| Thesis advisor | Bell, Timothy F |
| Thesis advisor | Gill, John T III |
| Advisor | Bell, Timothy F |
| Advisor | Gill, John T III |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Naoshin Haque. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2012. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2012 by Naoshin Haque
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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