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A uroral field-aligned acceleration Cluster results

Vaivads A. and Cluster Auroral Team. A uroral field-aligned acceleration Cluster results.

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A uroral field-aligned acceleration Cluster results

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  1. Vaivads A. and Cluster Auroral Team Auroral field-aligned accelerationCluster results André M., Backrud M., BuchertS., Olsson A.,Kistler L. M., Mouikis C., Quinn J. M., BosquedJ.-M., Cornilleau-Wehrlin N., Fazakerly A.,Marklund G., NewellP., Janhunen P., Rauch J.-L., Kadokura A., Taguchi M.

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

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

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

  5. Cluster/DMSP conjunction ovt s/c1 2001-04-28 1900-1940 Syowa S hemisphereMLT ~20Geomagnetically quiet3kV aurora~200W/m ~15km Plasma sheet boundary layerLow latitude boundary layer

  6. s/c1 2001-04-28 1915:30 UT -70 s/c 1 s/c 2,3 +2.5 min Auroral arc GMlat s/c 4 +3.5 min DMSP F14 +3.5min -80 85 GMlong 92 Ground mapping

  7. Region I DMSP F14 observations

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

  9. s/c3 spacecraft large scale

  10. s/c1..4 large scale

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

  12. sc1..4, small scale II Vps F SII SSII BCS

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

  14. zoom Aurora vs Magnetopause densityB

  15. Aurora E B S|| F

  16. zoom Aurora vs Magnetopause densityB

  17. Magnetopause E B S|| F

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

  19. Conclusions • 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) • Aurora vs Magnetopause infer E|| from Eperp

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