1. GEM (Student) Tutorial Jerry Goldstein, Rice University1
GEM (Student) Tutorial
June 23, 2002
Inner Magnetospheric Shielding, Penetration Electric Field, and the Plasmasphere
Jerry Goldstein, Rice University

2. 2 The Plasmasphere Ionospheric outflow: Plasmapause:
Populates p’sphere
D. L. Carpenter (Stanford)
“Whistler” wave studies
(ground-based)
Plasmapause:
boundary where dense, cold plasma ends
M-I Coupling: WG-1+2:
Ionospheric outflow
Wednesday 10:30-noon
Chairs: Lotko, Moore, Peterson
Chappell et al., OGO data

3. Magnetospheric Convection3
1. Generally sunward in the inner magnetosphere
2. Southward IMF

4. Magnetospheric Convection corotation (refilling) and4
Explain sharp ppause:
Boundary between
corotation (refilling) and
convection

5. 5 Magnetospheric Convection Plasmapause:
Density gradient marking outer boundary of plasmasphere--does not need to coincide with the instantaneous boundary between convection and co-rotation, because time scale for p’sphere response is slower than time scale of convection variations.
Plasmapause
Conv/corot boundary
WARNING: This is a highly oversimplified picture!
In reality, convection is usually very nonuniform and time-dependent
M-I Coupling: WG-2:
M’spheric convection
Tuesday 3:30-5:30pm
Chair: Ray Greenwald

6. The Extreme Ultraviolet (EUV) imager looks at the plasmasphere via
IMAGE Extreme Ultraviolet Imager (EUV) 6
MOVIE
EUV data 6:43-10:04, 5/24
REMOTE MEASUREMENT
The Extreme Ultraviolet (EUV) imager looks at the plasmasphere via

7. 7 Measuring the Plasmasphere IMAGE EUV in situ Cross-Phase
(ground magnetometer)
IM/S: WG-1:
Plasmaspheric structure
Monday 3:30-5:30pm (observations)
Chair: Dennis Gallagher
Tuesday 10:30-noon (techniques)
Chairs: Moldwin, Chi

8. Plasma Tails (“Plumes”) plasmaspheric tails (“plumes”)8
MI Coupling: WG-1:
plasmaspheric tails (“plumes”)
Monday 10:40-noon
Chair: Tom Moore

9. Plasma Tails 9
“Detached” plasma
The Duskside Bulge?

10. As Seen in the Ionosphere Space Weather Implications...
Plasma Tails 10
As Seen in the Ionosphere
Space Weather Implications...

11. 11
Shielding:
the plasmasheet,
Westward currents

12. Convection increase due to dawn-dusk E--> creates partial RC12
Shielding:
Convection increase due to dawn-dusk E--> creates partial RC

13. Partial RC closes in ionosphere via field-aligned currents13
Shielding:
Partial RC closes in ionosphere via field-aligned currents

14. Field-aligned currents create zonal charging.14
Shielding:
Field-aligned currents create zonal charging.

15. 15
Shielding:
Zonal charging creates potential drop across IM, creating dusk-dawn E that opposes/cancels dawn-dusk convection E

16. E-shielding exactly cancels E-convection
IM Shielding 16
Instead of this...
E-shielding exactly cancels E-convection
You get this...

17. E-shielding exactly cancels E-convection
IM Shielding 17
Shielding: 15 min - 1 hr
Thus, changes in Solar-wind/IMF conditions that occur more rapidly than the shielding time-scale allow convection field to penetrate past the shielding layer.
Perfect shielding might not occur even if conditions are steady, however. (See Dick Wolf’s tutorial.)
E-shielding exactly cancels E-convection

18. E-shielding exactly cancels E-convection
Penetration E-Fields 18
E-conv UP:
Sunward IM
plasma flow
E-conv DOWN
Tailward IM
plasma flow
E-shielding exactly cancels E-convection

19. E-shielding exactly cancels E-convection
Penetration E-Fields 19
E-conv UP:
Sunward IM
plasma flow
E-conv DOWN
Tailward IM
plasma flow
E-shielding exactly cancels E-convection

20. E-shielding exactly cancels E-convection
Penetration E-Fields 20
E-conv UP:
Sunward IM
plasma flow
E-conv DOWN
Tailward IM
plasma flow
E-shielding exactly cancels E-convection

21. 21 Geomagnetic Variation of Plasmapause Size/Shape of Plasmasphere
Depends on strength of convection
Swd IMF
Well-Shielded
Example: Plasmaspheric Erosion following sudden turn to southward IMF.

22. Geomagnetic (Kp) Variation of Plasmapause22
ISEE 1 (in situ)
OGO 5 (in situ)

23. Geomagnetic Variation of Plasmapause During/After Strong Convection23
IMAGE EUV data
Aug 11, 2000:
During/After Strong Convection
July 9, 2000:
Quiet

24. Chairs: Goldstein, Liemohn
IM E-Fields 24
IM/S: Tutorial:
I.M. E-fields
Monday 9:15-10am
Dick Wolf
IM/S: WG-1:
Near-Earth E-fields
Monday 1:30-3pm
Chairs: Goldstein, Liemohn

25. Simulated Penetration E-Fields Overshielding: Shoulder25
Overshielding: Shoulder
PDC

26. Simulated Penetration E-Fields Overshielding: Shoulder26
Overshielding: Shoulder
Penetration E needed to explain shoulder (and other meso-scale plasmaspheric structure).

27. Ring-Current and the IM E-field27
Penetration E needed to explain observed ring-current (RC) distribution.
IMAGE HENA
27-39 keV
CRCM Model, 32 keV
IM/S: WG-1:
RC/PS coupling (observations)
Tuesday 1:30-3pm
Chairs: C:son Brandt, Gallagher
RC/PS coupling (modeling)
Tuesday 3:30-5:30pm
Chairs: Liemohn, Reynolds

28. Conclusions 28
The plasmasphere is the torus of cold, dense, co-rotating plasma surrounding the Earth out to 3-5 RE, and is populated by ionospheric outflow.
The plasmapause is the outer boundary of the plasmasphere, but does not need to coincide with the instantaneous boundary between convection and co-rotation (the “last closed equipotential” or LCE), because the time scale for plasmaspheric response is slower than the time scale of convection variations.
Plasmaspheric tails form during periods of high activity (Kp high, or Dst low), and extend all the way down to the ionosphere. (They can therefore affect Earth communications.)
The inner magnetosphere tries to shield itself from the convection E-fields, but the buildup of an effective shielding layer takes time. If the convection strength varies faster than the shielding time scale (somewhere between 15 minutes and an hour), E-fields can penetrate past the shielding layer, and into the inner magnetosphere.
Penetration E-fields can affect both plasmaspheric populations (forming meso-scale structure such as tails, shoulders and/or bite-outs), and ring current distributions.