Amsterdam, Oct 2010

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

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

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)

Amsterdam, Oct 2010

Effect of frame rate9 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…..

Amsterdam, Oct 2010

Effect of frame rate9 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…..

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

Amsterdam, Oct 2010

Upward Streamer Formation

Starts later and from lower altitude lower than downward streamersNot present in all events

But: Upward streamers starts from luminous structures

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

Amsterdam, Oct 2010

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

Amsterdam, Oct 2010

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

Amsterdam, Oct 2010

Halo-streamer27 Aug 2009 09:15:23.086195 UT

Image time seriesDuration 2.5 msDownward velocity: Halo: 0.7 107 m/s Streamer: 2 107 m/s

Amsterdam, Oct 2010

Halo-streamer27 Aug 2009 09:05:06.089070 UT

Image time seriesDuration 2.5 msDownward velocity: Halo: 5 107 m/s Streamer: 1 107 m/s

Amsterdam, Oct 2010

Halo-streamer27 Aug 2009 09:15:23.086195 UT

Image time seriesDuration 2.5 msDownward velocity:

Halo: 0.7 107 m/sStreamer: 2 107 m/s

Streamer onset

Note: Streamer onset AFTER halo faded

Amsterdam, Oct 2010

Halo-streamer27 Aug 2009 09:05:06.089070 UT

Image time seriesDuration 2.5 msDownward velocity:

Halo: 5 107 m/sStreamer: 1 107 m/s

Streamer onset

Note: Again streamer onset AFTER halo faded

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).

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

Amsterdam, Oct 2010

Streamer onset relative to first frame09:15:23:

Streamer 1: 32 frames = 2.000 msStreamer 2: 43 frames = 2.687 msStreamer 3: 53 frames = 3.313 msStreamer 4: 28 frames = 1.750 msStreamer 5: 53 frames = 3.313 msStreamer 6: 63 frames = 3.938 ms

09:05:06:Streamer 1: 13 frames = 0.813 msStreamer 2: 16 frames = 1.000 msStreamer 3: 16 frames = 1.000 msStreamer 4: 19 frames = 1.188 ms

Jupiter

Amsterdam, Oct 2010

Conclusions

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 eventOlder 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

Amsterdam, Oct 2010

Extra slides

Amsterdam, Oct 2010

Streamer Formation

9 July 200506:33:11 UT 10,000 fps

Streamers move

Glow largely stationary

Amsterdam, Oct 2010

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

Amsterdam, Oct 2010

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