On the relationship between polar cap flows and the IMF W.A. Bristow, R.T. Parris, J. Spaleta, T....
-
date post
20-Dec-2015 -
Category
Documents
-
view
213 -
download
0
Transcript of On the relationship between polar cap flows and the IMF W.A. Bristow, R.T. Parris, J. Spaleta, T....
On the relationship between polar cap flows and the IMF
W.A. Bristow, R.T. Parris, J. Spaleta, T. TheurerGeophysical Institute, University of Alaska Fairbanks
McMurdo SuperDARN
• McMurdo Station SuperDARN built January 2010
• Station Latitude 77.88° South Geographic (~80° Magnetic)
• Magnetic Pole near center of FOV at ~1200 km range
Convection Maps
•Ruohoniemi and Baker convection mapping routine
•McMurdo data fill in region over magnetic pole
Convection Dependance• Examine
dependance Earth-Sun component of velocity on the IMF
• Use line of sight velocity to eliminate model influence
• Average of all LOS vectors where λ>85° and kr ∙kE-S > 0.9
Imposed Potential
Bow Shock
Magnetopause
Sheath
Vsw ≈300 km/sVi ≈ 1 km/s
Polar cap ~4000 km(OCB at 70°)
Expected Velocity• About 1-hour of IMF maps into
the polar cap at any given time
• Might expect ionospheric velocity to vary from place to place depending on solar wind mapping
• Except... sound speed in ionosphere
Expected Velocity• About 1-hour of IMF maps into
the polar cap at any given time
• Might expect ionospheric velocity to vary from place to place depending on solar wind mapping
• Except... sound speed in ionosphere
Expected Velocity
• For B≈50 µ T, oxygen n=1011, VA≈860 km/s
• 860 km/s >> 1km/s (flow speed)
• Flow is incompressible
- ∇∙v = 0