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Abstract Sprites have been recorded at ∼100,000 frames per second. One hundred and sixty five essentially vertically propagating streamers, 110 downward and 55 upward, have been selected for analysis. The initial velocity increase is exponential as predicted by theory. Growth rates could be determined for 76 downward and 46 upward propagating streamers, and, in individual streamers, they are independent of altitude. The average growth rate increases from 1.6 103in C‐sprites, to 2.6 103in carrots, to 8.4 103/s in jellyfish sprites. With a streamer model the driving electric field can be derived. Evaluating the field at 70 km altitude, we find fields of 98 (0.45 Ek), 121 (0.56 Ek), and 188 (0.87 Ek) V/m for the 3 sprite types, indicating that jellyfish sprites are the most energetic. High‐speed imaging can provide streamer growth rates and combined with a streamer model, the electric fields associated with various sprite features can be investigated.
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It's Not Easy Being Green: Kinetic Modeling of the Emission Spectrum Observed in STEVE's Picket Fence
Abstract Recent studies suggest that, despite its aurora‐like appearance, the picket fence may not be driven by magnetospheric particle precipitation but instead by local electric fields parallel to Earth's magnetic field. Here, we evaluate the parallel electric fields hypothesis by quantitatively comparing picket fence spectra with the emissions generated in a kinetic model driven by local parallel electric fields energizing ambient electrons in a realistic neutral atmosphere. We find that, at a typical picket fence altitude of 110 km, parallel electric fields between 40 and 70 Td (∼80–150 mV/m at 110 km) energize ambient electrons sufficiently so that, when they collide with neutrals, they reproduce the observed ratio of N2first positive to atomic oxygen green line emissions, without producing first negative emissions. These findings establish a quantitative connection between ionospheric electrodynamics and observable picket fence emissions, offering verifiable targets for future models and experiments.
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- PAR ID:
- 10504878
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 50
- Issue:
- 21
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1029/2023GL106073
