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

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b g b U

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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?