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Aurora, Substorms, and THEMIS D. G. Sibeck NASA/GSFC THEMIS Project Scientist
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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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Quartz Lake State Park, Alaska September 6, 1996
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January 6, 1998
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Aurora in Alaska
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March 11, 1998
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Aurora in Lapland
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Loomis Auroral Chart, 1860 You are here North Pole Elias Loomis Professor, Yale
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% Nights With Aurora You can also see aurora in Antarctica ! You are still here- you have a small but finite chance of seeing aurora
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Aurora over the Eastern U.S. You are here Sometimes the auroral oval brightens and expands over the continguous United States
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Good news: Auroras come furthest equatorward here on the East Coast Bad news: only during severe geomagnetic storms X
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Ground Magnetograms Example Summary: One Year of Kp index Sudden Commencement Compression Storm Disturbance 27 Day Solar Rotation
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When Should One Look? Spring Fall At or just before midnight, Spring or Fall
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SOHO: Solar Flares and Ejecta Our story begins at the Sun
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Solar Wind Model: Streams and Blast Waves
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Earth’s Magnetic Field
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Our Magnetic Shield
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Solar Wind Buffetting: Model Aurora
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Reconnection
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Cause of Aurora 120 km 60 km
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Reconnection Model
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Current Disruption
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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
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THEMIS Launch
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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
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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
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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)
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5 THEMIS S/C Line Up in Tail Once/4 Days Sun
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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
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Dedicated Array of US/Canadian Ground Observatories Provide Daily Auroral Movies
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First Auroral Mosaic Movie February 14, 2007 Dedicated Array of US and Canadian Ground Stations
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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
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