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Aurora. P. A. Delamere Laboratory for Atmospheric and Space Physics. Images by John Russell. John Russell. John Russell. John Russell. John Russell. John Russell. John Russell. John Russell. John Russell. John Russell. John Russell. John Russell. John Russell. John Russell.
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Aurora P. A. Delamere Laboratory for Atmospheric and Space Physics Images by John Russell
Noon Dawn Dusk Midnight
Solar Wind vsw ~ 400 km/s
Electron energy 1-10 keV; ~0.1 c • Acceleration process?
Charged particle motion in Earth’s magnetosphere • The combined effects of the Earth’s magnetic field will result in three • characteristic types of motion. Gyro: ~ millisecond Bounce: ~ 0.1-1.0 s Drift: ~ 1-10 minutes
The magnetopause controls the transport of • mass • momentum • energy • magnetic flux • into the magnetosphere
Open vs. closed configurations of the magnetosphere Magnetic reconnection Closed Open
Ionospheric convection: Open Magnetosphere Ruohoniemi and Baker, 1998
“Dungey cycle” Dungey, 1961
Ionospheric convection: Closed Magnetosphere Foerster et al., 1998 Axford and Hines, [1961]
Substorms • Storage and release of energy in the magnetosphere • Growth phase (energy accumulated in the magnetotail; southward IMF) • Expansion phase (energy released; auroral activity expands poleward and westward; 30-60 minutes) • Recovery phase (magnetosphere returns to original state; 1 to 2 hours; patchy aurora and quiet arcs)
Theta Aurora (northward IMF) DE 1 satellite