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Inner Magnetospheric Shielding, Penetration Electric Field, and the Plasmasphere

1. GEM (Student) Tutorial June 23, 2002. Inner Magnetospheric Shielding, Penetration Electric Field, and the Plasmasphere. Jerry Goldstein, Rice University. 2. The Plasmasphere. Ionospheric outflow: Populates p’sphere. D. L. Carpenter (Stanford) “Whistler” wave studies (ground-based).

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Inner Magnetospheric Shielding, Penetration Electric Field, and the Plasmasphere

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  1. 1 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: 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 Convection 3 1. Generally sunward in the inner magnetosphere 2. Southward IMF

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

  5. Magnetospheric Convection 5 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. IMAGEExtreme Ultraviolet Imager (EUV) 6 MOVIE EUV data 6:43-10:04, 5/24 REMOTE MEASUREMENT TheExtreme 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”) 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. Plasma Tails 10 As Seen in the Ionosphere Space Weather Implications...

  11. 11 Shielding: the plasmasheet, Westward currents

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

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

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

  17. 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. 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. 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. 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. Geomagnetic Variation of Plasmapause 21 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 Plasmapause 22 ISEE 1 (in situ) OGO 5 (in situ)

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

  24. 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 25 Overshielding: Shoulder PDC

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

  27. Ring-Current and the IM E-field 27 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.

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