MHD Model

1
MHD Model Iridium Birkeland Currents Comparison

• Birkeland currents from Iridium are globally
  distributed map to entire simulation volume
• Field aligned current is a direct MHD variable
  that is conserved across the high-to-low altitude
  mapping
• Comparison reveals specific ways that models need
  to be improved
• Results direct future modeling development

2
Iridium LFM-MHD Model Comparison

• Equatorward currents are missing in model
  missing physics
• Difference between low and high resolution
  numerical diffusion
• Nightside currents missing errors in modeled
  ionospheric conductivity

3
IMAGE-Iridium Inter-comparison

• Establish correlation of indirect remote sensing
  results with direct but global-scale in-situ
  observations
• Aurora indicate physical processes but the
  correspondence is not direct
• ? Occurrence of high latitude dayside aurora is
  governed by the Knight relation Korth et al.,
  2004.
• ? A northward IMF case particle energy input
  is only 1/8th of the total for northward IMF
  Poynting flux 45GW, particles 6 GW aurora do
  not show where the Poynting flux is.
• Ion pressure is almost certainly the source of
  Region 2. How well we understand the ring
  current and inner magnetosphere is well tested by
  comparing IMAGE/HENA Region 2 currents against
  Iridium results
• ? IMAGE/HENA currents are 10x too low and in
  the wrong place (by 6 hours) unless a realistic
  magnetic field is used Brandt et al., 2004.

4

• Particle and Poynting flux not coincident
• Precipitation power 6 GW
• Poynting flux 45 GW 7.5x particle

16 July 2000 1700-1800 UT
Iridum/DMSP
IMAGE/FUV -DMSP