Transcript Slide 1
M-I Coupling Physics: Issues, Strategy, Progress
Dartmouth
William Lotko, John Gagne, David Murr, John Lyon, Paul Melanson
The “Gap”
Issues
“Knight”
Dissipation
founded
1769
Cosponsored by NASA SECTP
EM Power In Ions Out
Empirical “Causal” Relations
A 2 RE spatial “gap” exists between the upper
boundary of TING and TIEGCM and the lower boundary
of LFM.
FO+ =
2.14x107·S||1.265
The gap is a primary site of plasma transport
where electromagnetic power is converted into fieldaligned electrons, ion outflows and heat.
r = 0.755
Modifications of the ionospheric conductivity by the
electron precipitation is included in global models via
the “Knight relation”; but other crucial physics is
missing;
Strangeway et al. ‘05
Progress
– 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.
Reconciled E mapping and collisionless Joule dissipation with Knight
relation in LFM
Conductivity Modifications
O +.
Developed and implemented empirical outflow model – O+ flux indexed to
EM power and electron precipitation flowing into gap from LFM (S|| Fe||)
The mediating transport processes occur on spatial
scales smaller than the grid sizes of the LFM and
TING/TIEGCM global models.
Initiated validation of LFM Poynting fluxes with global statistical results
from DE, Astrid, Polar and Iridium/SuperDARN events (Gagne thesis +
student poster by Melanson)
Evans et al., ‘77
Challenge: Develop models for subgrid processes using
the dependent, large-scale variables available from the
global models as causal drivers.
r = 0.721
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
Priorities
Energization Regions
Strategy
Zheng et al. ‘05
Implement multifluid LFM (!)
Global Effects of O+ Outflow
Implement CMW (2005) current-voltage relation in downward currents
(four transport models)
Include electron exodus from ionosphere conductivity depletion
1. Current-voltage relation in regions
of downward field-aligned current;
Accommodate upward electron energy flux into LFM
No
outflow
With
outflow
Advance empirical outflow model
2. Electron energization and
collisionless Joule dissipation in
Alfvénic regions – mainly cusp and
the auroral BPS regions;
Develop model for particle energization in Alfvénic regions
(scale issues!)
Need to explore frequency dependence of fluctuation spectrum at LFM
inner boundary
3. Ion transport in regions 1 and 2
above; and
Equatorial plane
Paschmann et al., ‘03
Parallel transport model for gap region (long term)
4. Ion outflow in the polar cap,
essentially a polar wind.
Alfvénic Electron
Where does the mass go?
Energization
Percent Change
in Mass Density
Ionospheric Parameters
(issues!)
1010 O+ / m2-s
Alfvénic Ion Energization
IMF
0
2
4
6
mW/m2
Energy Flux
T > 1 keV
> 0.5
Mean Energy
keV
n < 0.2/cm3
Northern
Outflow
P < 0.01 nPa
Chaston et al. ‘03
A/m2
J||
Alfvén Poynting Flux, mW/m2
IMF
12:00 UT
Keiling et al. ‘03
Lennartsson et al. ‘04
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