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Aurora, Substorms, and THEMIS

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

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Aurora, Substorms, and THEMIS

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  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, AlaskaSeptember 6, 1996

  4. January 6, 1998

  5. Aurora in Alaska

  6. March 11, 1998

  7. Aurora in Lapland

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

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

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

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

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

  13. When Should One Look? At or just before midnight, Spring or Fall Spring 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 RE 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. ? ? P2 P3 P4 P5 P1 Rarefaction wave Flows GBO THEMIS (Time History of Events and Macroscale Interactions during Substorms) distinguishes amongst competing substorm models 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. EFIs EFIa SCM ESA SST FGM Tspin=3s SPACECRAFT AND INSTRUMENTS 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 THEMISS/C Line Up in Tail Once/4 Days Sun

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

  30. Dedicated Array ofUS/Canadian Ground ObservatoriesProvide Daily Auroral Movies

  31. First Auroral Mosaic MovieFebruary 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/THEMIS • SCIENCE SITE: themis.ssl.berkeley.edu • EPO SITE: http://ds9.ssl.berkeley.edu/themis/no_flash.html

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