1. OpenGGCM Simulation vs THEMIS Observations in an Dayside Event Wenhui Li and Joachim Raeder University of New Hampshire Marit Øieroset University of California, Berkeley THEMIS 2008 UCLA

2. 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 R E ● No evidence for Kelvin-Helmholtz waves nor diffusion at the local magnetopause ● Particle distributions suggest double-high latitude reconnection involving the same field lines

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

4. OpenGGCM Simulation vs THEMIS-A Observations NIMF CDPS MP

5. OpenGGCM Simulation vs THEMIS-E Observations NIMF CDPS M.P.

6. OpenGGCM Simulation vs THEMIS-C Observations NIMF CDPS M.P.

7. OpenGGCM Simulation vs THEMIS-D Observations NIMF CDPS M.P.

8. OpenGGCM Simulation vs THEMIS-B Observations M.P. NIMF

9. 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 R E along THEMIS track Simulation: ~ 1.3 R E CDPL Open layer IMF

10. How the cold dense plasma layer forms? 1.Double high-latitude reconnection captures magnetosheath plasma Solar Wind

11. 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 path Frozen-in field lines Magnetic nulls (Li et. al. 2005)

12. 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

13. 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