M-I Coupling Physics: Issues, Strategy, Progress William Lotko, David Murr, John Lyon, Paul Melanson, Mike Wiltberger
The mediating transport processes occur on spatial scales smaller than the grid sizes of the LFM and TING/TIEGCM global
2. Ion transport in downward-current and Alfvénic regions;
Progress
Energization Regions
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Evans et al., ‘77
Conductivity Modifications
Dartmouth
founded1769
CollisionlessDissipation
Alfvénic ElectronEnergization
Energy Flux
Mean Energy
J||
mW
/m2
keV
A/m
2
Alfvén Poynting Flux, mW/m2Chaston et al. ‘03
EM Power In Ions Out
Zheng et al. ‘05
Implement and advance multifluid LFM (MFLFM!)
Implement CMW (2005) current-voltage relation in downward current regions
Include electron exodus from ionosphere conductivity depletion
Accommodate upward electron energy flux into LFM
Where doesthe mass go?
Alfvénic Ion Energization
Lennartsson et al. ‘04Keiling et al. ‘03
A 1 RE spatial “gap” exists between the upper boundary of TING (or TIEGCM) and the lower boundary of LFM.
The gap is a primary site of plasma transport where electromagnetic power is converted into field-aligned electron streams, ion outflows and heat.
Modifications of the ionospheric conductivity by the electron precipitation are included global MHD models via a “Knight relation”; but other crucial physics is missing:
– Collisionless dissipation in the gap region;
– Heat flux carried by upward accelerated electrons;
– Conductivity depletion in downward current regions;
– Ion parallel transport outflowing ions, esp. O+.
Develop model for particle energization in Alfvénic regions (scale issues!)
Need to explore frequency dependence of fluctuation spectrum at LFM inner boundary
Full parallel transport model for gap region (long term)
Advance empirical outflow model
Issues Reconciled E mapping and collisionless Joule dissipation with Knight relation in LFM
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 Iridium/SuperDARN events (Melanson thesis) and global statistical results from DE, Astrid, Polar (Gagne thesis)
Priorities
3. Collisionless Joule dissipation and electron energization in Alfvénic regions – mainly cusp and auroral BPS regions;
Strategy(Four transport models)
1. Current-voltage relation in regions of downward field-aligned current;
4. Ion outflow model in the polar cap (polar wind).
The “Gap”
Empirical “Causal” Relations
r = 0.755
FO+ = 2.14x107·S||1.265
r = 0.721
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Cosponsored by NASA HTP
Challenge: Develop models for subgrid processes using dependent, large-scale variables available from the global models as causal drivers.
Effects onMI Coupling
(issues!)
North South
8.5 simulation hours
AVERAGE ION NUMBER FLUXES
LFM with H+ Outflow (8 hours of CISM “Long Run”)
compared with
Polar Perigee Data(6 months Austral Summer)
Oct 97 – Mar 98
Polar perigee
DUSK
2 1025 ions/s 3 1025 ions/s 2-3 1024 ions/sFLUENCE
Log (Flux, # / m2-s)
9 10 11 12 13 9 10 11 12
Log (Flux, # / m2-s)
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