Comparing Sprite Currents with High-Speed Video Measurements
Abstract
Sprites are large scale electrical discharges taking place in the mesosphere, near the edge of space. They are triggered by quasi-electrostatic fields generated by (usually) positive cloud-to-ground lightning in underlying thunderstorms. Since their discovery 30 years ago, sprites have been extensively studied for their impact in mesospheric chemistry and potential as a tool for remote sensing of the mesosphere-lower ionosphere interface — a region difficult to access by conventional observation techniques. In that time, researchers have remotely observed sprites' optical, electromagnetic (EM), and acoustic signatures. They have learned that certain sprites do display an EM signature characteristic of a vertical current (1). However, measuring sprite currents remains challenging (2). It is unclear why some sprites present clear low-frequency current signatures, while others do not. A relationship between sprite current and its spatial structure or luminosity also remains unclear.
On June 2 and June 3, 2019, 52 sprites were captured with a V2010 camera recording at 100 kfps from Langmuir Laboratory (LL), in New Mexico. An extra sensitive ``slow-antenna'' (RMS noise < 0.2 V/m) located 25 miles East of LL, measured electric fields at 50 kS/sec simultaneous with the video observations. On June 3 alone, 25 sprites were between 425 and 475 km due East of the slow antenna. In 9 of these 25 cases, by examination of electric field records only (before the processed light curves were available) it was possible to correctly predict the time of peak intensity of the (optical) sprite to within 200 us. Peak field ranged from 500 mV/m to seven V/m, in some cases being nearly as large as the field from the parent positive lightning. We will continue to seek to understand the correlations between high-speed video and electric field features of the sprite itself. (1) Stanley et al., GRL, "Detection of daytime sprites via a unique sprite ELF signature" (2000). (2) Hu, Cummer, and Lyons, JGR, doi:10.1029/2006JD007939.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMAE31B3110C
- Keywords:
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- 3304 Atmospheric electricity;
- ATMOSPHERIC PROCESSES;
- 3324 Lightning;
- ATMOSPHERIC PROCESSES;
- 3394 Instruments and techniques;
- ATMOSPHERIC PROCESSES