1. Amsterdam, Oct 2010 Sprite Halo and Streamer Onset H. C. Stenbaek-Nielsen 1, M. G. McHarg 3, R. Haaland 2, and T. Kanmae 1 1) Geophysical Institute, University of Alaska Fairbanks 2) Fort Lewis College, Durango, Colorado 3) US Air Force Academy, Colorado Springs, Colorado

2. Amsterdam, Oct 2010 Halo and sprites at 1000 fps Halo unstructured – moves down Sprite streamers: first down and then up No halo with second sprite

3. Amsterdam, Oct 2010 Streamers form the extended structures Image: 18 Aug 1999, WIRO, WY ← Upward streamers ← Stationary glow ← Aircraft contrail ←Downward streamers (we need higher frame rates than 1000 fps to resolve streamers)

4. Amsterdam, Oct 2010 Effect of frame rate 9 July 2005 06:06:46 UT Streamers (almost) resolved at 50 μs (20,000 fps) 33 ms video 1 ms 50  s 10,000 fps makes a lot of difference…..

5. Amsterdam, Oct 2010 Effect of frame rate 9 July 2005 06:06:46 UT Streamers (almost) resolved at 50 μs (20,000 fps) 33 ms video 1 ms 50  s 10,000 fps makes a lot of difference…..

6. Amsterdam, Oct 2010 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. Amsterdam, Oct 2010 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. Amsterdam, Oct 2010 2009 Halo with structure Halos with structure observed from 14 km altitude 16,000 fps 20 microsec exposure 27 Aug 2009 09:05:06.089070 UT 27 Aug 2009 09:15:23.086195 UT

9. Amsterdam, Oct 2010 Halo-streamer 27 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. Amsterdam, Oct 2010 Halo-streamer 27 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. Amsterdam, Oct 2010 Halo-streamer 27 Aug 2009 09:15:23.086195 UT Image time series Duration 2.5 ms Downward velocity: Halo: 0.7 10 7 m/s Streamer: 2 10 7 m/s

12. Amsterdam, Oct 2010 Halo-streamer 27 Aug 2009 09:05:06.089070 UT Image time series Duration 2.5 ms Downward velocity: Halo: 5 10 7 m/s Streamer: 1 10 7 m/s

13. Amsterdam, Oct 2010 Halo-streamer 27 Aug 2009 09:15:23.086195 UT Image time series Duration 2.5 ms Downward velocity: Halo: 0.7 10 7 m/s Streamer: 2 10 7 m/s Streamer onset Note: Streamer onset AFTER halo faded

14. Amsterdam, Oct 2010 Halo-streamer 27 Aug 2009 09:05:06.089070 UT Image time series Duration 2.5 ms Downward velocity: Halo: 5 10 7 m/s Streamer: 1 10 7 m/s Streamer onset Note: Again streamer onset AFTER halo faded

15. Amsterdam, Oct 2010 Relative streamer onset: 09:15:23 UT 2 3 4 1 5 6 Jupiter 1 2 3 4 5 6 Strip time series: 80 consecutive images (5 ms).

16. Amsterdam, Oct 2010 Relative streamer onset: 09:15:23 UT 1 2 3 4 Strip time series: 40 consecutive images (2.5 ms). 1 2 3 4

17. Amsterdam, Oct 2010 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. Amsterdam, Oct 2010 Conclusions New findings: Sprite halos observed with structure Structure descends with halo –Observed velocities ~10 6 to 10 8 m/s Structures spawn downward streamers –Observed velocities ~10 6 to 10 8 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

19. Amsterdam, Oct 2010 Extra slides

20. Amsterdam, Oct 2010 Streamer Formation 9 July 2005 06:33:11 UT 10,000 fps Streamers move Glow largely stationary

21. Amsterdam, Oct 2010 Halo-streamer 27 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. Amsterdam, Oct 2010 Halo-streamer 27 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