J. Goldstein(1), R. A. Wolf(1), B. R. Sandel(2), T. Forrester (2), D. L. Gallagher (3), P. H. Reiff(1),

(1) Department of Physics & Astronomy, Rice University, Houston, TX (2) Lunar & Planetary Laboratory, University of Arizona, Tucson, AZ (3) NASA Marshall Space Flight Center, Huntsville, AL

Rapid response of the plasmasphere to changes in the IMF: Global plasmapause

electric field measurements by IMAGE EUV.

July 10, 2000 (day 192)

Nightside erosion

5:16-5:37 UT and 6:28-7:50

Plasmaspheric Erosion: July 10, 2000

(ABOVE) EUV images from observed interval of

plasmaspheric erosion.

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July 10, 2000 (day 192)

Nightside erosion

5:16-5:37 UT and 6:28-7:50

Plasmaspheric Erosion

(ABOVE) EUV images from observed interval of

plasmaspheric erosion.

QuickTime™ and a decompressor

are needed to see this picture.QuickTime™ and aGIF decompressor

are needed to see this picture.

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July 10, 2000 (day 192)

Erosion of nightside plasmasphere

Erosion: 5:16-5:37 UT and 6:28-7:50

During the times indicated, the plasmasphere was observed to shrink visibly.

BEFORE AFTER

July 10, 2000 (day 192)

Erosion of nightside plasmasphere

Erosion: 5:16-5:37 UT and 6:28-7:50(ABOVE) The plasmapause shapes from the EUV images have been mapped down to the magnetic equatorial plane. The effect of erosion is evident in the difference between the

“BEFORE” and “AFTER” plots.

BEFORE AFTER

What are the associated E-fields?

July 10, 2000 (day 192)What are the

associated E-fields?

Nightside erosion

5:16-5:37 UT and 6:28-7:50

Plasmaspheric Erosion

(ABOVE) EUV images from observed interval of

plasmaspheric erosion.

• Need to track motion of the plasmapause

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Goal: Follow “radial” motion

Plasmapause Tracking

Plasmapause Tracking

Goal: Follow “radial” motion

Velocity plasmapause

0.1 RE uncertainty in the tracking.

Nightside Erosion: What are we measuring?

nightside erosion

Electric Field ExtractionFirst we calculate the

velocity of a given point, using centered time

differencing.

Second-Order Finite-Difference

dRdt

⎡ ⎣ ⎢

⎤ ⎦ ⎥ T2

=R(T3) −R(T1)

T3 −T1

Then we get Electric Field E=-v X B.

(Assume dipole B)

Error SourcesTwo error sources from “euv_imtool”(1) manual centering(2) manual “clicking” on the p’pause

(3) Error from shape tracking algorithm.

• If X ~ 0.1 RE, then V~V (comparable).

Total Error

These 3 errors add up to “positional” uncertainty of ~0.1 RE per 10 minutes. Unfortunately, this isn’t much smaller than the flows we wish to measure. The E-field measurements are

therefore noisy, until we can polish the extraction and shape tracking routines.

(ABOVE) Snapshot from “euv_imtool”, the U. Arizona IDL

code used to extract plasmapauses from the EUV data,

and map them down to the magnetic equator.

Convection and Nightside Erosion

July 10, 2000

Convection and Nightside Erosion

July 10, 2000

Convection and Nightside Erosion

(TOP PLOT) 2D plot of Westward E-field vs. MLT and

UT.

Enhanced dawn-to-dusk E-field is concentrated in the pre-dawn

sector

July 10, 2000

Convection and Nightside Erosion

(TOP PLOT) 2D plot of Westward E-field vs. MLT and

UT.

Enhanced dawn-to-dusk E-field is concentrated in the pre-dawn

sector, and occurs in two bursts.

July 10, 2000

5:16-5:376:28-7:50

Convection and Nightside Erosion

(BOTTOM PLOT) Geotail BZ IMF

There are two corresponding bursts of southward IMF, which

presumably triggered the convection.

The Geotail data has been time shifted by 6.5 minutes to account

for propagation, and an additional 30 minutes, which might be

“reconfiguration time.”

July 10, 2000

Convection and Nightside Erosion

July 10, 2000

sample here

The Eastward E-field [in units of mV/m X 10] is overlaid on the

time-shifted Geotail BZ IMF

_____________________________

The agreement between the two is quite good.

Convection and Nightside Erosion

1. Post-midnight E-concentration

(PMEC)

2. Close correspondence

with delayed IMF

June 2, 2001 (day 153)

Nightside erosion

00:54-2:05 UT and 4:18-5:09

Plasmaspheric Erosion II: June 2, 2001

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June 2, 2001 (day 153)

1. Post-midnight E-concentration

(PMEC)

Plasmaspheric Erosion II: June 2, 2001

June 2, 2001 (day 153)

1. Post-midnight E-concentration

(PMEC)

2. Close correspondence

with delayed IMF

Plasmaspheric Erosion II: June 2, 2001

Shielding

Overshielding (antisunward flow)

Undershielding (sunward flow)

E-shielding exactly

cancels E-convection

E-conv picks up:Sunward plasma flow

in inner msphere

E-conv decreases:Tailward plasma flow

in inner msphere

Penetration E-Fields: IM Shielding

Overshielding (antisunward flow)

Overshielding

ShieldingE-shielding

exactly cancels E-convection

E-conv decreases:Tailward plasma flow

in inner msphere

Overshielding: MSM Electric Fields

PMEC

“dawnside eddy”

Overshielding: Plasmaspheric Shoulder

Outward flow here

Corotation to here

Undershielding

ShieldingUndershielding (sunward flow)E-shielding

exactly cancels E-convection

E-conv picks up:Sunward plasma flow

in inner msphere

18:45

“Bite-out”

Bite-out forms

MSM density, day 78, 18:45 MSM pot., day 78, 18:45

March 19, 2001 biteout

Bite-out

18:45

PMEC

“Bite-out”

Bite-out forms

00:35

MSM density, day 79, 00:30

EUV image, day 79, 00:35

drainage tail

drainage tail

March 20, 2001 (cont.)

Bite-out

Bite-out

“Biteout”

Bite-out forms

2:38

MSM density, day 79, 2:45

EUV image, day 79, 2:38

drainage tail

drainage tail

March 20, 2001 (cont.)

Bite-out

Bite-out

EUV and the dawnside eddy

“dawnside eddy”

MSM: IM Response, March 31, 2001 storm

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IM Response to March 31, 2001 storm

IM Response to March 31, 2001 storm

IM Response to March 31, 2001 storm

IM Response to March 31, 2001 storm

MSM-EUV comparisonMOVIE

Conclusions

(1) EUV permits limited extraction of E-fields (or velocity fields).

(2) EUV E-fields, MSM simulations together: (a) rapid response of PS to IMF (b) PMEC leads to formation of shoulders, bite-outs