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High-Frame-Rate Imaging of Halo and Sprite Streamers: Insights from 2005 and 2009 Observations

This study explores the dynamics of halo and sprite streamers using high-frame-rate imaging techniques. Observations from July 9, 2005, at 10,000 fps and August 27, 2009, at 16,000 fps reveal distinct formation processes for downward and upward streamers. Key findings include the appearance of streamers from luminous structures and the relationship between streamers and halo phenomena. The results emphasize the necessity of high frame rates to capture the intricate details of these atmospheric electrical events, contributing to our understanding of their velocities and timing.

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High-Frame-Rate Imaging of Halo and Sprite Streamers: Insights from 2005 and 2009 Observations

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  1. Sprite Halo and Streamer Onset H. C. Stenbaek-Nielsen1, M. G. McHarg3, R. Haaland2, and T. Kanmae1 1) Geophysical Institute, University of Alaska Fairbanks 2) Fort Lewis College, Durango, Colorado 3) US Air Force Academy, Colorado Springs, Colorado

  2. Halo and sprites at 1000 fps Halo unstructured – moves down Sprite streamers: first down and then up No halo with second sprite

  3. Streamers form the extended structures (we need higher frame rates than 1000 fps to resolve streamers) Image: 18 Aug 1999, WIRO, WY ← Upward streamers ← Stationary glow ← Aircraft contrail ←Downward streamers

  4. Effect of frame rate9 July 2005 06:06:46 UT 10,000 fps makes a lot of difference….. 1 ms 50 ms 33 ms video Streamers (almost) resolved at 50 μs (20,000 fps)

  5. Effect of frame rate9 July 2005 06:06:46 UT 10,000 fps makes a lot of difference….. 1 ms 50 ms 33 ms video Streamers (almost) resolved at 50 μs (20,000 fps)

  6. Downward Streamer Formation Data seem to tell the following story: Streamers appear out of background and move down leaving in its path a largely stationary glow But: No halo visible in these examples

  7. Upward Streamer Formation • Starts later and from lower altitude lower than downward streamers • Not present in all events • But: Upward streamers starts from luminous structures

  8. 2009 Halo with structure 27 Aug 2009 09:05:06.089070 UT • Halos with structure observed from 14 km altitude • 16,000 fps • 20 microsec exposure 27 Aug 2009 09:15:23.086195 UT

  9. Halo-streamer27 Aug 2009 09:15:23.086195 UT • Images at 16,000 fps, 20 μs exposure • Sequence of events: • Elve descends • Halo with structure descends • Downward moving streamers form from halo structures

  10. Halo-streamer27 Aug 2009 09:05:06.089070 UT • Images at 16,000 fps, 20 μs exposure • Sequence of events: • Elve descends • Halo with structure descends • Downward moving streamers form from halo structures

  11. Halo-streamer27 Aug 2009 09:15:23.086195 UT Image time series Duration 2.5 ms Downward velocity: Halo: 0.7 107 m/s Streamer: 2 107 m/s

  12. Halo-streamer27 Aug 2009 09:05:06.089070 UT Image time series Duration 2.5 ms Downward velocity: Halo: 5 107 m/s Streamer: 1 107 m/s

  13. Halo-streamer27 Aug 2009 09:15:23.086195 UT Image time series Duration 2.5 ms Downward velocity: Halo: 0.7 107 m/s Streamer: 2 107 m/s Streamer onset Note: Streamer onset AFTER halo faded

  14. Halo-streamer27 Aug 2009 09:05:06.089070 UT Image time series Duration 2.5 ms Downward velocity: Halo: 5 107 m/s Streamer: 1 107 m/s Streamer onset Note: Again streamer onset AFTER halo faded

  15. Relative streamer onset:09:15:23 UT 3 4 Jupiter 2 3 4 1 5 6 1 5 2 6 Strip time series: 80 consecutive images (5 ms).

  16. 1 Relative streamer onset:09:15:23 UT 2 3 1 2 3 4 4 Strip time series: 40 consecutive images (2.5 ms).

  17. Streamer onset relative to first frame 09:15:23: Streamer 1: 32 frames = 2.000 ms Streamer 2: 43 frames = 2.687 ms Streamer 3: 53 frames = 3.313 ms Streamer 4: 28 frames = 1.750 ms Streamer 5: 53 frames = 3.313 ms Streamer 6: 63 frames = 3.938 ms 09:05:06: Streamer 1: 13 frames = 0.813 ms Streamer 2: 16 frames = 1.000 ms Streamer 3: 16 frames = 1.000 ms Streamer 4: 19 frames = 1.188 ms Jupiter

  18. New findings: Sprite halos observed with structure Structure descends with halo Observed velocities ~106 to 108 m/s Structures spawn downward streamers Observed velocities ~106 to 108 m/s Time delay for streamer onset vary within event Older observations: Sprites start with downward streamers Sometimes followed by upward streamers Upward streamers from existing structure Prompt sprite onset at higher altitude than delayed sprites Conclusions

  19. Extra slides

  20. Streamer Formation Streamers move Glow largely stationary 9 July 2005 06:33:11 UT 10,000 fps

  21. Halo-streamer27 Aug 2009 09:15:23.086195 UT • Images at 16,000 fps, 20 μs exposure • Sequence of events: • Elve descends • Halo with structure descends • Downward moving streamers form from halo structures

  22. Halo-streamer27 Aug 2009 09:05:06.089070 UT • Images at 16,000 fps, 20 μs exposure • Sequence of events: • Elve descends • Halo with structure descends • Downward moving streamers form from halo structures

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