MI Coupling Physics: Issues, Strategies, Progress William Lotko 1, Peter Damiano 1, Mike Wiltberger...
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MI Coupling Physics: Issues, Strategies, Progress William Lotko 1 , Peter Damiano 1 , Mike Wiltberger 2 , John Lyon 1,2 , Slava Merkin 3 , Oliver Brambles 1 , Binzheng Zhang 1 , Katie Garcia 3 Dartmouth Founded 1769 The Event Steady SW, IMF B z < 0 SMC interval (in the sense of O’Brien et al, 2002) Data from Korth et al. (2004) Waters et al. (2004) One-Fluid LFM Simulations Grid: 53x48x64 200 km 200 km at ionosphere Extract E and B at inner boundary Calculate δB B - B dip (dipole field) Calculate S = E x δB·b dip /μ 0 , where 1-hour Map S from LFM inner boundary to ionosphere Compare simulation PC , J and S at ionosphere with SuperDARN-Iridium Weimer (2005) DMSP track data The mediating transport processes occur on spatial scales smaller than the grid sizes of the LFM and TIEGCM global models. Energization Regions Paschmann et al., ‘03 Evans et al., ‘77 Conductivity Modifications A 1 R E 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 electron precipitation are included in 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 + . Issues Challenge: Develop models for subgrid processes using large-scale variables from the global models as causal drivers. The “Gap” Collisionless Dissipation EM Power In Ions Out Zheng et al. ‘05 Strategy (Four transport models) 1. Current-voltage relation in regions of downward field- aligned current; 2. Ion transport in downward-current and Alfvénic regions; 3. Collisionless Joule dissipation and electron energization in Alfvénic regions – mainly cusp and auroral BPS regions; 4. Ion outflow model in the polar cap (polar wind). Empirical “Causal” Relations r = 0.755 F O+ = 2.14x10 7 ·S || 1.265 r = 0.721 Strangeway et al. ‘05 Advance multifluid LFM (MFLFM) Advance empirical outflow model Develop polar wind outflow model Develop Alfvénic electron precipitation model Prioriti es DMSP Track Comparisons Ion Outflows Lennartsson et al. ‘04 12 Abe et al. ‘03 12 Superthermal Thermal Poynting Fluxes DC 12 Keiling et al. ‘03 Alfvénic Olsson et al. ‘04 12 Observed Statistical Distributions Develop model for particle energization in Alfvénic regions (scale issues!) Explore frequency dependence of fluctuations at LFM inner boundary Full parallel transport model for gap region (long term) Progress Reconciled E mapping and parallel Joule dissipation with Knight relation in LFM Power Flow Through the Gap Gap Dissipation Poynting flux S ||m G ap G ap m J n S P P P P G ap G ap P E J d G ap G ap 2 i i P E Jd J J 2 2 P H c P Ionospheric Dissipation 2 1 sin i J c J P dh I 0 1 sin n n i P u J B dh I 0 i i n J E u B with Effect of Global Electrodynamics = 0 0 2 3 Alfvénic Ion Energization via Validations of LFM Poynting fluxes with Iridium-SuperDARN events (Melanson) and global statistical results from DE, Astrid, Polar (Gagne) Chaston et al. ‘03 Alfvénic Electron Energization Alfvén Poynting Flux, mW/m 2 Energy Flux Mean Energy mW/m 2 keV A/m 2 J || 1 Developed and implemented empirical outflow model with outflow flux indexed to EM power and electron precipitation flowing into gap from LFM (S || F e|| )
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Transcript of MI Coupling Physics: Issues, Strategies, Progress William Lotko 1, Peter Damiano 1, Mike Wiltberger...
MI Coupling Physics: Issues, Strategies, Progress William Lotko1, Peter Damiano1, Mike Wiltberger2, John Lyon1,2, Slava Merkin3, Oliver Brambles1, Binzheng Zhang1, Katie Garcia3
DartmouthFounded 1769
The Event
Steady SW, IMF Bz < 0
SMC interval (in the sense of O’Brien et al, 2002)
Data from Korth et al. (2004) Waters et al. (2004)
One-Fluid LFM Simulations
Grid: 53x48x64 200 km 200 km
at ionosphere
Extract E and B at inner boundary
Calculate δB B - Bdip (dipole field)
Calculate S = E x δB·bdip/μ0 , where 1-hour
Map S from LFM inner boundary to ionosphere
Compare simulation PC, J and S at ionosphere with
SuperDARN-Iridium Weimer (2005) DMSP track data
The mediating transport processes occur on spatial scales smaller than the grid sizes of the LFM and TIEGCM global models.
Energization Regions
Pas
chm
ann
et a
l., ‘0
3
Evans et al., ‘77
Conductivity Modifications
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 electron precipitation are included in 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+.
Issues
Challenge: Develop models for subgrid processes using large-scale variables from the global models as causal drivers.
The “Gap”
CollisionlessDissipation
EM Power In Ions Out
Zheng et al. ‘05
Strategy(Four transport models)
1. Current-voltage relation in regions of downward field- aligned current;
2. Ion transport in downward-current and Alfvénic regions;
3. Collisionless Joule dissipation and electron energization in Alfvénic regions – mainly cusp and auroral BPS regions;
4. Ion outflow model in the polar cap (polar wind).
Empirical “Causal” Relations
r = 0.755
FO+ = 2.14x107·S||1.265
r = 0.721
Str
ange
way
et a
l. ‘0
5Advance multifluid LFM (MFLFM)
Advance empirical outflow model
Develop polar wind outflow model
Develop Alfvénic electron precipitation model
Priorities
DMSPTrack
Comparisons
Ion
Outflows
Lennartsson et al. ‘04
12Abe et al. ‘03
12
Superthermal
Thermal
Poynting
Fluxes
DC
12
Keiling et al. ‘03
Alfvénic
Olsson et al. ‘04
12
Observed
Statistical
Distributions
Develop model for particle energization in Alfvénic regions (scale issues!)
Explore frequency dependence of fluctuations at LFM inner boundary
Full parallel transport model for gap region (long term)
Progress
Reconciled E mapping and parallel Joule dissipation with Knight relation in LFM
Power Flow Through the Gap
Gap Dissipation
Poynting flux S||m
Gap Gapm J nS P P P P
Gap GapP E J d
Gap Gap
2i i
P E J d
J J
2 2P H
cP
Ionospheric Dissipation
21sin
iJ
c
JP dh
I
0
1sinn n iP u J B dhI
0i i nJ E u B M
with
Effect of
Global Electrodynamics
= 0
0
2
3
Alfvénic Ion Energization
via
Validations of LFM Poynting fluxes with Iridium-SuperDARN events (Melanson) and global statistical results from DE, Astrid, Polar (Gagne)
Ch
ast
on
et
al. ‘
03
Alfvénic ElectronEnergization
Alfvén Poynting Flux, mW/m2
Energy Flux
Mean Energy
mW
/m2
keV
A
/m2
J||
1
Developed and implemented empirical outflow model with outflow flux indexed to EM power and electron precipitation flowing into gap from LFM (S|| Fe||)
