IssuesA 2 RE spatial “gap” exists between the upper boundary of TING and TIEGCM and the lower boundary of LFM.

The gap is a primary site of plasma transport where electromagnetic power is converted into field-aligned electrons, ion outflows and heat.

Modifications of the ionospheric conductivity by the electron precipitation is included in global models via the “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+.

M-I Coupling Physics: Issues, Strategy, Progress William Lotko, John Gagne, David Murr, John Lyon, Paul Melanson

Alfvénic Electron

Energization

Energization Regions

Ionospheric Parameters(issues!)

Where does the mass go? Percent Changein Mass Density

The mediating transport processes occur on spatial scales smaller than the grid sizes of the LFM and TING/TIEGCM global models.

Challenge: Develop models for subgrid processes using the dependent, large-scale variables available from the global models as causal drivers.

Strategy(four transport models)

1. Current-voltage relation in regions of downward field-aligned current;

2. Electron energization and collisionless Joule dissipation in Alfvénic regions – mainly cusp and the auroral BPS regions;

3. Ion transport in regions 1 and 2 above; and

4. Ion outflow in the polar cap, essentially a polar wind.

Progress

Reconciled E mapping and collisionless Joule dissipation with Knight relation in LFM

Developed and implemented empirical outflow model – O+ flux indexed to EM power and electron precipitation flowing into gap from LFM (S|| Fe||)

Initiated validation of LFM Poynting fluxes with global statistical results from DE, Astrid, Polar and Iridium/SuperDARN events (Gagne thesis + student poster by Melanson)

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Conductivity Modifications

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Energy Flux

Mean Energy

J||

mW

/m2

keV

A/m

2

Alfvén Poynting Flux, mW/m2

Alfvénic Ion Energization

“Knight”Dissipation

EM Power In Ions Out

Priorities

Implement multifluid LFM (!)

Implement CMW (2005) current-voltage relation in downward currents

Include electron exodus from ionosphere conductivity depletion Accommodate upward electron energy flux into LFM

Advance empirical outflow model

Develop model for particle energization in Alfvénic regions (scale issues!)

Need to explore frequency dependence of fluctuation spectrum at LFM inner boundary

Parallel transport model for gap region (long term)

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Keiling et al. ‘03 Lennartsson et al. ‘04

Zheng et al. ‘05

Equatorial plane

Global Effects of O+ Outflow IMF

Empirical “Causal” Relations

Strangeway et al. ‘05

r = 0.755

FO+ = 2.14x107·S||1.265

r = 0.721

12:00 UT

IMF 0 2 4 10

1010 O+ / m2-s

6 8

NorthernOutflow

With outflow

No outflow

T > 1 keV

> 0.5

n < 0.2/cm3

P < 0.01 nPa

Chaston, C.C., J. W. Bonnell, C. W. Carlson, J. P. McFadden, R. E. Ergun, and R. J. Strangeway, Properties of small-scale Alfvén waves and accelerated electrons from FAST, J. Geophys. Res. 108(A4), 8003, doi:10.1029/2002JA009420, 2003 Cran-McGreehin, A.P., and A.N. Wright, Current-voltage relationship in downward field-aligned current region, J. Geophys. Res. 110, A10S10, doi:10.1029/2004JA010870, 2005 Evans,

D.S., N. Maynard, J. Trøim, T. Jacobsen, and A. Egeland, A., Auroral vector electric field and particle comparisons 2. Electrodynamics of an arc, J. Geophys. Res. 82(16), 2235–2249, 1977 Keiling, A., J.R. Wygant, C.A. Cattell, F.S. Mozer, and C.T. Russell, The global morphology of wave Poynting flux: Powering the aurora, Science 299, 383-386, 2003 Lennartsson, O.W., and H.L. Collin, W.K. Peterson, Solar wind control of Earth’s H+

and O+ outflow rates in the 15-eV to 33-keV energy range, J. Geophys. Res. 109, A12212, doi:10.1029/2004JA010690, 2004 Paschmann, G., S. Haaland and R. Treumann, Auroral Plasma Physics, Kluwer Academic Publishers, Boston/Dordrecht/London, 2003 Strangeway, R.J., R. E. Ergun, Y.-J. Su, C. W. Carlson, and R. C. Elphic, Factors controlling ionospheric outflows as observed at intermediate altitudes, J. Geophys. Res. 110,

A03221, doi:10.1029/2004JA010829, 2005 Zheng, Y., T.E. Moore, F.S. Mozer, C.T. Russell and R.J. Strangeway, Polar study of ionospheric ion outflow versus energy input, J. Geophys. Res. 110, A07210, doi:10.1029/2004JA010995, 2005

Cosponsored by NASA SECTP

The “Gap”