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Dynamics and Structure of SubAuroral Polarization Streams

Evgeny MishinBoston College ISR

MIT Haystack Observatory November 7, 2005

With contributions from & thanks to Bill Burke

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OUTLINE

• Prompt SAPS response to the substorm onset and solar wind oscillations: DMSP and ISR

• SAPS-wave structures: The benchmark of RC injections

• Plasma waves and heating/acceleration in the ring current- plasmasphere overlap

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Solar wind & IMF oscillations[Mishin et al., 2002]

Sept 25, 1998

12-min oscillations

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A stormtime substorm

The substorm onset at 08:18 UT

21.0 MLT& 66 MLat

dipolarization

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Response to the substorm onset

SAPS 15.5 MLT

Before

after

SAPS

Onset: 0818 UT

21.0 MLT & L~6

SAPS: 0830 UT

15.5 MLT & L~3

L~3 & MLT~5.5

in 12 min

VR~ 30 km/s

Vϕ~ 15 km/s

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Solar wind- & IMF-driven SAPS- modulation

~12-min oscillations

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Structured SAPS

PS equatorial boundary

Onset at ~0350 UT

Nov 6, 2001

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Strong SAPSWS: The benchmark of RC injections

DMSP F14, April 6, 2000

[Mishin et al., 2004]

RC ions

“Strong”

oscillations ≥ mean

Density troughs

ions

electrons

SAPSWS:

Meso-scale Alfven wave

Electron temperature

Ion temperature

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RC-injection events: Waves CRRES & DMSP, June 5, 1991

Plas

ma

Shee

t bou

ndar

y

Ions

Ele

ctro

ns

NOSEL H R

UHR

Suprathermal electrons &

ions

Alfvenwave-

structure

SAPSWS

Density trough

SAPSWS maps to

the wave structure observed by

CRRES at 17 MLTinner edge

[Mishin & Burke, 2005]

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Alfve’n waves in RC- plasmasphere overlap: Current-convective instability

|| ||' /( )ek J enω ω= − g

[Volkov& Maltsev, 1986]

(Static approximation)

|| ||' /( )e Dk J en k Uω ω ⊥= − −g gTransverse motion of

RC cloud favors generation of

short-scale modes

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SAPSWS evolution after substorm injections June 5, 1991 [Mishin and Burke, 2005]

Density troughs

ions

electrons

substorm onsets

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Electron Heating

Collisional heating rate

WantedHeating source of plasmaspheric electrons at

the RC’s inner edge

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Diamagnetic current LH instability

diamagnetic current

LaBelle& Treumann [1988]

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Plasma heating/acceleration: LH collapse

LH collapse threshold

near RC’s inner edge

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SUMMARY (“RC/SAPS”)

•Substorm injections quickly affect already existing SAPS.

•SAPS wave-structures (SAPSWS) follow injections of RC particles and are generated by the current-convective instability at the forefront.

•Precipitating ion & electron fluxes, elevated electron temperatures, and highly-structured density troughs accompany the SAPSWS.

•The energy source for the electron heating/acceleration equatorward of the SAPSWS is likely the LH turbulence driven by the diamagnetic current at the RC inner edge.

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Trough & elevated Te

trou

gh

trou

gh

Foster et al [1994]

Elevated Te is due to heattransport from the plasmasphere

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Plasmaspheric plasma heating/acceleration near the RC’s inner edge

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Elevated Te and density troughs

Hot electrons pump N2 vibrational levels.

CT rate coefficient increases, and fast recombination of NO+

leads to plasma depletion.

Tro

ugh

dept

h

Topside ionosphere

Charge Transfer

*2 ( )O N V NO N+ ++ → +

400 km

105

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Density trough

Scenario of the high-Te related density trough