1. Aurora, Substorms, and THEMIS D. G. Sibeck NASA/GSFC THEMIS Project Scientist

2. Outline What do aurora look like? Where do aurora occur? When do aurora occur? Why do aurora occur? How will THEMIS help us understand aurora? Where can I find out more information?

3. Quartz Lake State Park, Alaska September 6, 1996

4. January 6, 1998

5. Aurora in Alaska

6. March 11, 1998

7. Aurora in Lapland

8. Loomis Auroral Chart, 1860 You are here North Pole Elias Loomis Professor, Yale

9. % Nights With Aurora You can also see aurora in Antarctica ! You are still here- you have a small but finite chance of seeing aurora

10. Aurora over the Eastern U.S. You are here Sometimes the auroral oval brightens and expands over the continguous United States

11. Good news: Auroras come furthest equatorward here on the East Coast Bad news: only during severe geomagnetic storms X

12. Ground Magnetograms Example Summary: One Year of Kp index Sudden Commencement Compression Storm Disturbance 27 Day Solar Rotation

13. When Should One Look? Spring Fall At or just before midnight, Spring or Fall

14. SOHO: Solar Flares and Ejecta Our story begins at the Sun

15. Solar Wind Model: Streams and Blast Waves

16. Earth’s Magnetic Field

17. Our Magnetic Shield

18. Solar Wind Buffetting: Model Aurora

19. Reconnection

20. Cause of Aurora 120 km 60 km

21. Reconnection Model

22. Current Disruption

23. THEMIS Science: –Identify when and where substorms (building blocks of storms) begin –Distinguish between competing models –Understand substorm physics Impact on Society –Predict when and where substorms occur –Understand and guard against substorm-related increases in radiation belt particle flux, communication disruptions, and current surges in power/pipelines

24. THEMIS Launch

25. Orbital Information Launched at Sunset, February 17, 2007 Presently: all 5 s/c on almost identical orbits: –1.1 x 14.7 R E with inclination 14.4°, period 31 hours, separated by 100’s to 1000’s km –Apogees between the Sun and the Earth, studying radiation belts and the outer boundary of the Earth’s magnetic field Future…each has its own special orbit to help pinpoint when and where substorm onset occurs

26. Flows THEMIS (Time History of Events and Macroscale Interactions during Substorms) distinguishes amongst competing substorm models ? Rarefaction wave ? P2 P3 P4 P5 GBO P1 Careful positioning of 5 well-instrumented probes and dedicated array of ground observatories Allows us to impartially test two competing models and determine the cause of substorms

27. SPACECRAFT AND INSTRUMENTS SST ESA EFIa EFIs FGM SCM T spin =3s FIVE IDENTICALLY-INSTRUMENTED SPACECRAFT (128 kg), EACH CARRYING: ESA: Electrostatic analyzer measures 0.003-30 keV ions/electrons (UCB) SST: Solid state telescopes measures 0.03-6 MeV ions and electrons (UCB) FGM: Fluxgate magnetometer measures magnetic field to 128 Hz (Germany) SCM: Search coil magnetometer measures 0.001 - 4 kHz magnetic field (France) EFI: Electric field instrument on wires and axial booms 0.0003 - 400 kHz (UCB)

28. 5 THEMIS S/C Line Up in Tail Once/4 Days Sun

29. TH-GBOs: High resolution & sensitivity Onset: 11:12:51UT, Intensification: 11:18:30UT First on THD Last on THE 2nd on THB 3rd on THA Magnetic Field Timing a Substorm THE THA THB THD THC Sun March 23, 2007

30. Dedicated Array of US/Canadian Ground Observatories Provide Daily Auroral Movies

31. First Auroral Mosaic Movie February 14, 2007 Dedicated Array of US and Canadian Ground Stations

32. FOR MORE INFORMATION Principle Investigator: Vassilis Angelopoulos (NASA/JPL) Project Scientist: David Sibeck (NASA/GSFC) NASA SITE WWW.NASA.GOV/THEMISWWW.NASA.GOV/THEMIS SCIENCE SITE: themis.ssl.berkeley.edu EPO SITE: http://ds9.ssl.berkeley.edu/themis/no_flash.html