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1. mmijjum/Production_Rates_Calculator: 01_22 - SPRITE

   https://doi.org/10.5281/zenodo.14721533  

   Mijjum, Moshammat; Bristol, Katie (January 2025, Zenodo)

   This is an update to the SPRITE framework presented in Mijjum et al. (2025) (up to date as of 01/22/2025). This update fixes a typo in the example inputs spreadsheet. PREVIOUS DESCRIPTION: This is latest (as of 10/28/2024) of the production rate calculator (SPRITE) described in Mijjum et al. (2024) (in review with Geochemistry, Geophysics and Geosystems). Model will calculate scaling factors and exposure ages from 0-70 Ma using a time-varying magnetic field (paleointensity), paleoclimate, and latitude (paleolatitude). Code contributions were made by Moshammat Mijjum (@mmijjum), Katie Bristol (@katiebristol), and Richard Bono (@rkbono), manuscript contributions from Marissa Tremblay (@mtrems), Nat Lifton, and Courtney Sprain.  

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2. Observed Sprite Streamer Growth Rates

   https://doi.org/10.1029/2024GL112537  

   Stenbaek‐Nielsen, H C; McHarg, M G; Liu, N Y (January 2025, Geophysical Research Letters)

   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 E_k), 121 (0.56 E_k), and 188 (0.87 E_k) 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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3. Relationship Between Sprite Current and Morphology

   https://doi.org/10.1029/2020ja028930  

   Contreras‐Vidal, L.; Sonnenfeld, R. G.; da Silva, C. L.; McHarg, M. G.; Jensen, D.; Harley, J.; Taylor, L.; Haaland, R.; Stenbaek‐Nielsen, H. (March 2021, Journal of Geophysical Research: Space Physics)

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4. Sprite Durations Measured With a Neuromorphic Sensor

   https://doi.org/10.1029/2024GL109353  

   Smith, B.; McHarg, M_G; da_Silva, C_L; Sonnenfeld, R_G; Koile, J.; Leal, A_F_R; Jones, I_R (June 2024, Geophysical Research Letters)

   Abstract Neuromorphic sensors have inherently‐fast speeds and low data rates, which potentially make them ideal for the observation of transient sources, such as lightning and sprites. Particularly, for remote observations. In this article, we report the first observations of sprites from the ground with a neuromorphic sensor. These observations are accompanied by measurements with established instruments such as low‐light level and high‐frame rate cameras. We determine that neuromorphic sensors can capture sprites and determine their duration to an accuracy of roughly 6 ms. Average sprite durations were found to be 55 ms within our data set. We have also ascertained that sprites may be too dim for the neuromorphic sensors to resolve the internal spatiotemporal dynamics, at least without the aid of intensifiers. 

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5. Enhancement of Green Ghosts Due To Recurrence of Sprite Element

   https://doi.org/10.1029/2024GL108397  

   Huang, Xin; Lu, Gaopeng; Liu, Feifan; Cheng, Zhengwei; Lucena, Frankie; Liu, Yu; Xue, Xianghui; Wang, Yongping; Cohen, Morris B; Ashcraft, Thomas; et al (October 2024, Geophysical Research Letters)

   Abstract We examined three observations of green emission events (labeled as event A, B and C, respectively) associated with red sprites as captured by amateurs. In all cases, the green emissions were recorded atop of red sprite. Based on the location of causative strokes and background star fields for events A and B, their altitudes are confined between 88 and 100 km, with the maximum brightness at 90.7 and 95.5 km, respectively. Events B and C were lit up for a second time after the recurrence of a sprite element, extending their duration to approximately 1,084 ms and 732.6 ms, much longer than that (about 500 ms) for event A; the intensity of green emissions was also enhanced due to sprite recurrence. It is inferred that the recurrence of sprite elements could affect the ambient condition by further increasing electron density and strengthening the electric field for the ghost production. 

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