Tail substorm dynamics captured by HENA

1
Tail substorm dynamics captured by HENA

• HENA observes ENAs coming from 12 Re in the
  magnetotail.
• The observed tail propagates Earthward at
  substorm dipolarization.
• Correlated with auroral substorm onset.
• So far observed for 4 October 2000 and 19
  September 2000 storm.

SUN
DUSK
DAWN
Accelerated ions reach lower altitudes. Auroral
onset
Dipolarization Ions accelerated earthward
evacuating plasmasheet densities
Plasmasheet starts refilling. Edge moving out.
Plasmasheet restored.
Ions drifting in from nightside filling the
plasmasheet
2
Supporting measurements

• The GOES satellite sees dipolarization when tail
  starts propagating Earthward
• The LANL geosynchronous sees particle injection

GOES
3
Equatorial ion distributions
4 OCT 2000 MAINPHASE
Sun contamination
Dipolarization and injections reach geosynchronou
s. Auroral onset.
Injection complete
Stretched tail field. Dense plasmasheet
Ions drifts earthward in dipolarization
E-field faster than they can be replenished from
tail convection field
Flux increase due to conservation of adiabatic
invariance