Aurora, Substorms, and THEMIS

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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, AlaskaSeptember 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
North Pole
You are here
Elias Loomis Professor, Yale
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Nights With Aurora
You are still here- you have a small but finite
chance of seeing aurora
You can also see aurora in Antarctica!
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Aurora over the Eastern U.S.
Sometimes the auroral oval brightens and expands
over the continguous United States
You are here
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Good news Auroras come furthest equatorward here
on the East CoastBad news only during severe
geomagnetic storms
X
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Ground Magnetograms
27 Day Solar Rotation
Example
Sudden Commencement Compression
Summary One Year of Kp index
Storm Disturbance
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When Should One Look?
At or just before midnight, Spring or Fall
Spring
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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Earths 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 RE with inclination 14.4, period 31
  hours, separated by 100s to 1000s km
• Apogees between the Sun and the Earth, studying
  radiation belts and the outer boundary of the
  Earths magnetic field
• Futureeach has its own special orbit to help
  pinpoint when and where substorm onset occurs

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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 A
llows us to impartially test two competing
models and determine the cause of substorms
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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)
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5 THEMISS/C Line Up in Tail Once/4 Days
Sun
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Timing a Substorm
March 23, 2007
3rd on THA
TH-GBOs High resolution sensitivity Onset
111251UT, Intensification 111830UT
2nd on THB
THE THA THB THD THC
Magnetic Field
Sun
First on THD
Last on THE
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Dedicated Array ofUS/Canadian Ground
ObservatoriesProvide Daily Auroral Movies
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First Auroral Mosaic MovieFebruary 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/THEMIS
• SCIENCE SITE themis.ssl.berkeley.edu
• EPO SITE http//ds9.ssl.berkeley.edu/themis/no_fl
  ash.html