Remote sensing and statistical analysis of the lightning-ionosphere interaction
Abstract/Contents
- Abstract
- Lightning is an extremely frequent phenomenon and an important part of the global electrical circuit with an average of 2000 active storms globally every day and an average flash rate of 40-50 flashes per second. Each lightning stroke radiates an intense electromagnetic pulse (EMP) in the VLF/LF frequency band (300 Hz---300 kHz). This EMP propagates efficiently in the earth-ionosphere waveguide and can be measured long distances away on the ground, in excess of several thousand kilometers. The upwardly directed part of the EMP interacts with and heats plasma in the Earth's ionosphere. Some of this energy propagates through the ionosphere where it enters the magnetosphere as a whistler-mode wave which may resonantly interact with energetic electrons in the Earth's radiation belts. Intense lightning EMPs may produce brief optical flashes known as ``elves'' in the lower part of the ionosphere ($\sim$88km altitude). Elves, first discovered in 1991, appear as rapidly expanding rings of light centered about the causative lighting stroke. They have durations of less than 1 ms and radial extents up to several hundred kilometers. In this work, we present ground-based observations of elves made using an optical free-running photometer along with VLF/LF observations of the lightning EMP magnetic field. We use these experimental observations to investigate the properties of the lightning return stroke that control the production of optical elve emissions. Two summers of data containing observations of over six hundred elves along with the LF magnetic field of the associated lightning are analyzed. By training a classifier on features of the EMP ground wave, we find that we are able to accurately predict whether or not a stroke produced an elve. Additionally, we show that the geometric features of elves can be used to estimate the current return stroke speed of lightning. This estimation constitutes the first experimental measurement of the return stroke speed that relates directly to the current propagation rather than its optical manifestation. Finally, we use data from the GLD360 lightning geolocation network to extrapolate the global elve production rate and to estimate the amount of ionospheric heating due to lightning.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2015 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Blaes, Patrick R |
|---|---|
| Associated with | Stanford University, Department of Electrical Engineering. |
| Primary advisor | Gill, John T III |
| Primary advisor | Inan, Umran S |
| Thesis advisor | Gill, John T III |
| Thesis advisor | Inan, Umran S |
| Thesis advisor | Marshall, Robert |
| Advisor | Marshall, Robert |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Patrick R. Blaes. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2015. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2015 by Patrick Ryan Blaes
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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