EGS XXVII General Assembly

Nice, France, April 2001

AAuroral field-aligned uroral field-aligned accelerationacceleration

Cluster resultsCluster results

Vaivads A. and Cluster Auroral Team 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.

slide 2.

Outline

Cluster orbitCluster orbit 28 April 2001 DMSP/Cluster conjunction28 April 2001 DMSP/Cluster conjunction Aurora vs MagnetopauseAurora vs Magnetopause ConclusionsConclusions

slide 3.

Cluster on auroral field lines

Auroral acceleration

GeneratorOrbit in March

after Parks(1991)

Energy transportTemporal evolutionEquipotential line closure

Orbit in September

Generator E.j <0?particle flux?

slide 4.

How does equipotential lines close?

Mozer 2001 Janhunen et al., 2001

Cluster Cluster

FAST

Polar

DMSP

slide 5.

Cluster/DMSP conjunction

S hemisphereMLT ~20Geomagnetically quiet3kV aurora~200W/m ~15km

ovt s/c1 2001-04-28 1900-1940

Syowa

Plasma sheet boundary layerLow latitude boundary layer

slide 6.

Ground mapping

GMlong85 92

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

slide 7.

DMSP F14 observations

Region I

slide 8.

DMSP F14 observations

•Arc width ~10-15 km in ionosphere

•Inetgrated energy flux ~200 W/m. (max 20mW/m2)

•Acceleration potential ~3kV.

slide 9.

s/c3 spacecraft large scale

slide 10.

s/c1..4 large scale

slide 11.

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

EE

EE

EE

EE

VpsVps

slide 12.

sc1..4, small scale II

VpsVps

SSIIII

SSIIII

BBCSCS

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

slide 14.

Aurora vs Magnetopause

zoomdensity B

slide 15.

Aurora

EE

BB

SS||||

slide 16.

Aurora vs Magnetopause

zoom

density B

slide 17.

Magnetopause

EE

BB

SS||||

slide 18.

Aurora vs Magnetopause

•Can we infer E|| from measurements of Eperp

•OUTstanding small scales vs BIG scales

slide 19.

Conclusions

Cluster/DMSP conjunctionCluster/DMSP conjunctionenergy flux balanceenergy flux balance

DMSP ~220W/m / Cluster ~70-200W/mDMSP ~220W/m / Cluster ~70-200W/magreement with U-potentialagreement with U-potential

DMSP ~3kV / Cluster ~2-5kVDMSP ~3kV / Cluster ~2-5kVtop of the auroral cavitytop of the auroral cavityions or waves cannot power aurora (in this case)ions or waves cannot power aurora (in this case)

Aurora vs MagnetopauseAurora vs Magnetopauseinfer Einfer E|||| from E from Eperpperp