Transcript Slide 1

2
MI Coupling Physics: Issues, Strategies, Progress
3
Energization Regions
1
Dartmouth
Founded 1769
William Lotko1, Peter Damiano1, Mike Wiltberger2, John Lyon1,2, Slava Merkin3, Oliver Brambles1, Binzheng Zhang1, Katie Garcia3
A 1 RE spatial “gap” exists between the upper boundary of
TING (or TIEGCM) and the lower boundary of LFM.
Reconciled E mapping and parallel Joule dissipation with Knight relation in LFM
The gap is a primary site of plasma transport where
electromagnetic power is converted into field-aligned electron
streams, ion outflows and heat.
DMSP
Track
Comparisons
Modifications of the ionospheric conductivity by electron
precipitation are included in global MHD models via a “Knight
relation”; but other crucial physics is missing:
Global Electrodynamics
Developed and implemented empirical outflow model
with outflow flux indexed to EM power and electron
precipitation flowing into gap from LFM (S||  Fe||)
Validations of LFM Poynting fluxes with IridiumSuperDARN events (Melanson) and global statistical
results from DE, Astrid, Polar (Gagne)
Paschmann et al., ‘03
– Collisionless dissipation in the gap region;
The mediating transport processes occur on spatial
scales smaller than the grid sizes of the LFM and
TIEGCM global models.
Gap
E J d
 J i    J 2i
PGap  
Gap
E  J  d

SMC interval (in the sense of O’Brien et al, 2002)
  0
Data from  Korth et al. (2004)  Waters et al. (2004)
One-Fluid LFM Simulations
The “Gap”
Conductivity Modifications
Grid: 53x48x64  200 km  200 km
at ionosphere
Evans et al., ‘77
dh
Extract E and B at inner boundary
c
1
Pn 
u  J  B dh
sin I  n i 0
Effect of 
Calculate δB  B - Bdip (dipole field)
Calculate S = E x δB·bdip/μ0 , where  1-hour
with

J i    Ei  un  B0
 
c 
P
2
P
Map S from LFM inner boundary to ionosphere

Compare simulation PC, J and S at ionosphere with
2
H
SuperDARN-Iridium
 Weimer (2005)
 DMSP track data
Advance multifluid LFM (MFLFM)
1. Current-voltage relation in regions of downward fieldaligned current;
Develop model for particle energization
in Alfvénic regions (scale issues!)
Advance empirical outflow model
 Explore frequency dependence of
fluctuations at LFM inner boundary
2. Ion transport in downward-current and Alfvénic regions;
Develop polar wind outflow model
3. Collisionless Joule dissipation and electron energization in
Alfvénic regions – mainly cusp and auroral BPS regions;
Develop Alfvénic electron precipitation model
Collisionless
Dissipation
4. Ion outflow model in the polar cap (polar wind).
Priorities
Strategy
EM Power In  Ions Out
Full parallel transport model for gap
region (long term)
12
12
DC
Thermal
(Four transport models)
Alfvénic Electron
Energization
Alfvénic Ion Energization
via
Empirical “Causal” Relations
Poynting
Ion
Fluxes
Outflows
12
Olsson et al. ‘04
Abe et al. ‘03
Energy Flux
mW/m2
P Gap  
J 2i
Steady SW, IMF Bz < 0
Challenge: Develop models for subgrid processes using large-scale
variables from the global models as causal drivers.
Ionospheric Dissipation
1
PJ 
sin I
The Event
O+.
12
Mean Energy
Zheng et al. ‘05
r = 0.721
Strangeway et al. ‘05
r = 0.755
Alfvénic
Keiling et al. ‘03
keV
Observed
Statistical
Distributions
FO+ =
2.14x107·S||1.265
Superthermal
Lennartsson et al. ‘04
J||
A/m2
Gap Dissipation
– Ion parallel transport  outflowing ions, esp.
Progress
 = 0
Chaston et al. ‘03
S m  P Gap  PGap  PJ  Pn
– Conductivity depletion in downward current regions;
Issues
Power Flow Through the Gap
Poynting flux S||m
– Heat flux carried by upward accelerated electrons;
Alfvén Poynting Flux, mW/m2