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Rapid response of the plasmasphere to changes in the IMF: Global plasmapause electric field measurements by IMAGE EUV. J. Goldstein (1) , R. A. Wolf(1), B. R. Sandel(2), T. Forrester (2), D. L. Gallagher (3), P. H. Reiff (1) , - PowerPoint PPT Presentation
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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.
QuickTime™ and a decompressor
are needed to see this picture.
MOVIE
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.
MOVIE MOVIE
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
QuickTime™ and a decompressor
are needed to see this picture.
MOVIE
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
QuickTime™ and a decompressor
are needed to see this picture.
MOVIE
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
MOVIE
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