Post on 20-Dec-2015
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OpenGGCM Simulation vs THEMIS Observationsin an Dayside Event
Wenhui Li and Joachim RaederUniversity of New Hampshire
Marit ØierosetUniversity of California, Berkeley
THEMIS 2008 UCLA
THEMIS Observations on 06/03/2007(Øieroset et. al. 2008)
● Northward IMF with strong By
during ~15:25 -- ~17:00 UT
● THEMIS-B in the magnetosheath
● THEMIS-A, C, D and E detect a layer of nearly-stagnant magnetosheath plasma (T ~ 1 keV, N ~ 3-6 cm-3) attached to the magnetopause on closed field lines
● From TH-D to TH-A, magnetospheric ion and electron flux increases
● Thickness of the layer ~ 0.9 RE
● No evidence for Kelvin-Helmholtz waves nor diffusion at the local magnetopause
● Particle distributions suggest double-high latitude reconnection involving the same field lines
OpenGGCM Simulation vs THEMIS Observations
-- Thickness of the cold dense plasma layer
values on the line passing THA at 16:30 UT
~1.3
THEMIS: ~ 1.1 RE along THEMIS trackSimulation: ~ 1.3 RE
CDPL
Open layer
IMF
How the cold dense plasma layer forms?
1. Double high-latitude reconnection captures magnetosheath plasma
Solar Wind
How the cold dense plasma layer forms?
2. New closed flux tubes slowly convect around magnetopause toward nightside -- results in a balance of inflow and outflow at dayside magnetopause and form a cold dense plasma layer
Solar wind
An entry flow pathFrozen-in field lines
Magnetic nulls
(Li et. al. 2005)
Summary
● THEMIS observed cold dense plasma layer in dayside closed field attached to magnetopause
● The multi spacecrafts estimated the thickness of the cold dense plasma layer to be ~0.9 RE
● An OpenGGCM simulation reproduces the THEMIS observations
● Observations and simulation analysis indicate that double high-latitude reconnection causes the formation of this cold dense plasma layer