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

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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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