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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,

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Presentation on theme: "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,"— Presentation transcript:

1 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.

2 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. MOVIE

3 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. MOVIE

4 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

5 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. BEFOREAFTER What are the associated E-fields?

6 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 MOVIE

7 Goal: Follow “radial” motion Plasmapause Tracking

8 Goal: Follow “radial” motion Velocity  plasmapause  0.1 RE uncertainty in the tracking.

9 Nightside Erosion: What are we measuring? nightside erosion

10 Electric Field Extraction First we calculate the velocity of a given point, using centered time differencing. Second-Order Finite-Difference Then we get Electric Field E= - v X B. (Assume dipole B)

11 Error Sources Two 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 R E, 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.

12 Convection and Nightside Erosion July 10, 2000

13 Convection and Nightside Erosion July 10, 2000

14 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

15 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, :16-5:376:28-7:50

16 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

17 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.

18 Convection and Nightside Erosion 1. Post-midnight E-concentration (PMEC) 2. Close correspondence with delayed IMF

19 June 2, 2001 (day 153) Nightside erosion 00:54-2:05 UT and 4:18-5:09 Plasmaspheric Erosion II: June 2, 2001 MOVIE

20 June 2, 2001 (day 153) 1. Post-midnight E-concentration (PMEC) Plasmaspheric Erosion II: June 2, 2001

21 June 2, 2001 (day 153) 1. Post-midnight E-concentration (PMEC) 2. Close correspondence with delayed IMF Plasmaspheric Erosion II: June 2, 2001

22 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

23 Overshielding (antisunward flow) Overshielding Shielding E-shielding exactly cancels E-convection E-conv decreases: Tailward plasma flow in inner msphere

24 Overshielding: MSM Electric Fields PMEC “dawnside eddy”

25 Overshielding: Plasmaspheric Shoulder Outward flow here Corotation to here

26 Undershielding Shielding Undershielding (sunward flow) E-shielding exactly cancels E-convection E-conv picks up: Sunward plasma flow in inner msphere 18:45

27 “Bite-out” Bite-out forms MSM density, day 78, 18:45MSM pot., day 78, 18:45 March 19, 2001 biteout Bite-out 18:45 PMEC

28 “Bite-out” Bite-out forms 00:35 MSM density, day 79, 00:30 EUV image, day 79, 00:35 drainag e tail March 20, 2001 (cont.) Bite-out

29 “Biteout” Bite-out forms 2:38 MSM density, day 79, 2:45 EUV image, day 79, 2:38 drainag e tail March 20, 2001 (cont.) Bite-out

30 EUV and the dawnside eddy “dawnside eddy”

31 MSM: IM Response, March 31, 2001 storm MOVIE

32 IM Response to March 31, 2001 storm

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36 MSM-EUV comparison MOVIE

37 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


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