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EGS XXVII General Assembly Nice, France, April 2001 Auroral field-aligned acceleration Cluster results Vaivads A. and Cluster Auroral Team André M., Backrud.

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Presentation on theme: "EGS XXVII General Assembly Nice, France, April 2001 Auroral field-aligned acceleration Cluster results Vaivads A. and Cluster Auroral Team André M., Backrud."— Presentation transcript:

1 EGS XXVII General Assembly Nice, France, April 2001 Auroral field-aligned acceleration Cluster results Vaivads A. and Cluster Auroral Team André M., Backrud M., Buchert S., Olsson A., Kistler L. M., Mouikis C., Quinn J. M., Bosqued J.-M., Cornilleau-Wehrlin N., Fazakerly A., Marklund G., Newell P., Janhunen P., Rauch J.-L., Kadokura A., Taguchi M.

2 slide 2. Outline l Cluster orbit l 28 April 2001 DMSP/Cluster conjunction l Aurora vs Magnetopause l Conclusions

3 slide 3. Cluster on auroral field lines Auroral acceleration Generator Orbit in March after Parks(1991) Energy transport Temporal evolution Equipotential line closure Orbit in September Generator E.j <0? particle flux?

4 slide 4. How does equipotential lines close? Mozer 2001 Janhunen et al., 2001 Cluster FAST Polar DMSP

5 slide 5. Cluster/DMSP conjunction S hemisphere MLT ~20 Geomagnetically quiet 3kV aurora ~200W/m ~15km ovt s/c1 2001-04-28 1900-1940 Syowa Plasma sheet boundary layer Low latitude boundary layer

6 slide 6. Ground mapping GMlong8592 GMlat -70 -80 s/c 4 +3.5 min DMSP F14 +3.5min s/c 1 s/c1 2001-04-28 1915:30 UT s/c 2,3 +2.5 min Auroral arc

7 slide 7. DMSP F14 observations Region I

8 slide 8. DMSP F14 observations Arc width ~10-15 km in ionosphere Inetgrated energy flux ~200 W/m. (max 20mW/m2) Acceleration potential ~3kV.

9 slide 9. s/c3 spacecraft large scale

10 slide 10. s/c1..4 large scale

11 slide 11. s/c 1..4, small scale (2 min, ~100km) E E E E Vps

12 slide 12. sc1..4, small scale II Vps  S II  S II B CS

13 slide 13. Other energy sources H+ [eV] Efl [mW/m2] 40 W/m Ions as energy source ?  SII [mWs/m2] Waves ? (1-10Hz) 1.5 W/m

14 slide 14. Aurora vs Magnetopause zoom density B

15 slide 15. Aurora E B  S ||

16 slide 16. Aurora vs Magnetopause zoom density B

17 slide 17. Magnetopause E B  S ||

18 slide 18. Aurora vs Magnetopause Can we infer E || from measurements of Eperp OUTstanding small scales vs BIG scales

19 slide 19. Conclusions l Cluster/DMSP conjunction energy flux balance DMSP ~220W/m / Cluster ~70-200W/m agreement with U-potential DMSP ~3kV / Cluster ~2-5kV top of the auroral cavity ions or waves cannot power aurora (in this case) l Aurora vs Magnetopause infer E || from E perp


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