geospace gap: issues, strategy, progress cosponsored by nasa htp lotko - gap region introduction...
Post on 20-Dec-2015
214 views
TRANSCRIPT
Geospace Gap: Issues, Strategy, Progress Cosponsored by NASA HTP
Lotko - Gap region introduction
Lotko - Outflow simulations
Melanson - LFM/SuperDARN/Iridium comparisons
Murr - GEM Challenge on MI coupling
Lyon - Development of Multifluid LFM
Wang - Development of CMIT and TING/TIEGCM
Merkin - Proposed studies using multifluid LFM/RCM
Lotko - Proposed studies using multifluid CMIT
Geospace Gap: Issues, Strategy, Progress
A 1-2 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 electrons, ion outflows and heat.
Modifications of the ionospheric conductivity by the electron precipitation are included in global MHD 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+.
The mediating transport processes occur on spatial scales smaller than the grid sizes of the LFM and TING/TIEGCM global
Issues
Challenge: Develop models for subgrid processes using dependent, large-scale variables available from the global models as causal drivers.
The Geospace: Issues, Strategy, Progress
Plasma Redistribution
Foster et al. ‘05
The Geospace: Issues, Strategy, Progress
Ring Current & Plasma Sheet Composition
Nose et al. ‘05
Simulated O+/H+ Outflow into Magnetosphere
Winglee et al. ‘02
The Geospace: Issues, Strategy, Progress
Geospace Gap: Issues, Strategy, Progress
Pa
sch
ma
nn
e
t a
l., ‘0
3
Geospace Gap: Issues, Strategy, Progress
Evans et al., ‘77
Conductivity Modifications
Geospace Gap: Issues, Strategy, Progress
Cavity formation on bottomside is more efficient than at F-region peak
Bottomside gradient steepens
Doe et al. ‘95
Simulated Time Variation of Ne Profile in Downward Current Region
Geospace Gap: Issues, Strategy, Progress
“Knight” Dissipation
1. Current-voltage relation in regions of downward field-aligned current†;
2. Collisionless Joule dissipation and electron energization in Alfvénic regions – mainly cusp and auroral BPS regions;
3. Ion transport in regions 1 and 3;
4. Ion outflow model in the polar cap (polar wind).
Kei
ling
et a
l. ‘0
3
Lenn
arts
son
et a
l. ‘0
4
Geospace Gap: Issues, Strategy, Progress
Zheng et al. ‘05
Cusp & Auroral-Polar Cap Boundary Region
EM Power IN Ions OUT
Geospace Gap: Issues, Strategy, Progress
Alfvénic ElectronEnergization
Energy Flux
Mean Energy
J||
mW
/m2
keV
A/m
2
Alfvén Poynting Flux, mW/m2Chaston et al. ‘03
Empiricalapproach?
LFM’s large gridannihilates most of the relevant Alfvénic powernear its inner boundary
Geospace Gap: Issues, Strategy, Progress
Empirical approach to ionospheric outflow
r = 0.755
FO+ = 2.14x107·S||1.265
r = 0.721
Strangeway et al. ‘05
Geospace Gap: Issues, Strategy, Progress
Outflows in cusp and
auroral polar cap boundary
OUTFLOW ALGORITHM
Geospace Gap: Issues, Strategy, Progress
Greatest change in lobes and inner magnetosphere
Magnetopause appears more variable8
101
0 O+ / m
2-s
10
0246
NorthernOutflow
Equatorial plane
Global Effects of O+ Outflow IMF
With outflow
No outflow
Geospace Gap: Issues, Strategy, Progress
Where does the mass go?
T > 1 keV
> 0.5
n < 0.2/cm3
P < 0.01 nPa
Ionospheric effects?
Geospace Gap: Issues, Strategy, Progress
Geospace Gap: Issues, Strategy, Progress
PathwaysTo
Upwelling
Strangeway et al. ‘05
Geospace Gap: Issues, Strategy, Progress
, 2
,,
2 2
( )
ˆ
1 1 1ˆ ˆ
( ) ( ) ( ) ( ) ( ( )) ( )
e nn e
O
nQ Ln n
t
VB
V P Pn m n m
n e n N n O n N n N n O
D
Dt
L e
V
V
E BV b
b g b U
E
Geospace Gap: Issues, Strategy, Progress
Where does the mass go?
T > 1 keV
> 0.5
n < 0.2/cm3
P < 0.01 nPa
Ionospheric effects?