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

THEMIS Observations on 06/03/2007(Øieroset et. al. 2008)

OpenGGCM Simulation vs THEMIS-A Observations

NIMF CDPS MP

OpenGGCM Simulation vs THEMIS-E Observations

NIMF CDPS M.P.

OpenGGCM Simulation vs THEMIS-C Observations

NIMF CDPS M.P.

OpenGGCM Simulation vs THEMIS-D Observations

NIMF CDPS M.P.

OpenGGCM Simulation vs THEMIS-B Observations

M.P. NIMF

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

Additional Information

A comprehensive study of magnetosphere under northward IMF conditions using OpenGGCM simulations can been found in:

Solar wind plasma entry into the magnetosphere under northward IMF conditions

Li et. al. 2008, JGR, newly published