3. On the relationship between polar cap flows and the IMF W.A. Bristow, R.T. Parris, J. Spaleta, T. Theurer Geophysical Institute, University of Alaska Fairbanks

4. 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

5. The Geometry Radar at MLT midnight ~730 UT ~1800 SLT Radar at MLT Noon ~1930 UT ~0600 SLT

6. The Geometry Terminator 100 km 200 km 300 km

7. The Geometry 200 km Shadow Height

8. Convection Maps Ruohoniemi and Baker convection mapping routine McMurdo data fill in region over magnetic pole

9. 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 k r ∙ k E-S > 0.9

10. Convection Dependance

19. Average Correlation

20. Convection Dependance

23. Expected Velocity Ohms Law In ionosphere B≈50µT E???

24. Imposed Potential

25. Bow Shock Magnetopause Sheath V sw ≈300 km/s V i ≈ 1 km/s Polar cap ~4000 km (OCB at 70°)

26. 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

27. 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

28. Expected Velocity For B≈50 µ T, oxygen n=10 11, V A ≈860 km/s 860 km/s >> 1km/s (flow speed) Flow is incompressible  ∇ ∙v = 0

29. Uniformity?

30. Divergence Free?

31. Conclusion In some intervals the observed polar cap convection is strongly correlated with the IMF. Next step - quantify relation to IMF. Determine when good correlation is expected Quantify velocity divergence, vorticity, etc.