1. Storm-Time Dynamics of the Inner Magnetosphere: Observations of Sources and Transport Michelle F. Thomsen Los Alamos National Laboratory 27 June 2003

2. Outline Introduction importance of the plasma sheet why geosynchronous orbit What observations tell us about plasma sheet properties What observations tell us about plasma sheet transport What observations tell us about plasma sheet losses

3. The inner magnetosphere is bathed in the plasma sheet. The plasma sheet is the source population for the ring current and the radiation belts. Importance of the plasma sheet

4. Plasma Sheet Enhancements -> Storm-Time Ring Current n psh Dst

5. Storm-Time Ring Current: Relation to Plasma Sheet From Thomsen et al., Geophys. Res. Lett., 25, 3481, 1998. SW Electric FieldPlasma Sheet DensityBoth

6. Why geosynchronous orbit? Gateway to the inner magnetosphere: Near the dynamic boundary between the inner and outer magnetosphere (the inner edge of the plasma sheet) Perfect location to monitor the plasma sheet material that is delivered into the inner magnetosphere Provides window on many relevant phenomena Well-populated with satellites over a long period of time (ATS, GEOS-2, GOES, LANL, etc.)

7. Current Geosynchronous Configuration

8. Objective: What can be learned about inner magnetospheric dynamics by observations at the geosynchronous gateway? nature of the plasma sheet transport losses

9. What observations tell us about plasma-sheet properties Variability Composition Relationship to solar wind properties Superdense intervals

10. Plasma-sheet variability: Minutes to hours Hot-Ion Density (cm -3 )

11. Plasma-sheet variability: Day to Day

12. Plasma Sheet Variability With Activity Kp Log(-Dst)

13. Plasma-sheet variability: Over a solar cycle

14. Overview: Plasma Sheet Sources

15. Inferred plasma sheet composition: Solar Cycle Variation

16. Relation to Solar Wind Properties

17. Relation to Solar Wind Properties [Borovsky et al., 1998]

18. Cold, dense plasma sheet under northward IMF From Terasawa et al., GRL, p. 935, 1997 (see also Oieroset et al., 2003)

19. Cold, dense plasma sheet: Source of superdense near-Earth plasma sheet? (after Borovsky et al., 1997)

20. Superdense near-Earth plasma sheet: Northward IMF + Interplanetary Shock (from Thomsen et al., 2003)

21. Superdense plasma sheet: Northward IMF origin 30 events (from Thomsen et al., 2003)

22. Solar Wind Contributions to the Plasma Sheet B z <0 B z B z >0 B z >0 -> B z <0

23. Alfvén boundaries Bursty convection enhancements Propagation of convection enhancements What observations tell us about plasma-sheet transport

24. Overview: Plasma Sheet Transport Convection +Gradient/Curvature Drift

25. Plasma Sheet Transport: Ion Drift Trajectories separatrix

26. Plasma Sheet Transport: Electron Drift Separatrices

27. Kp-Dependent Convection Geosynchronous Ion Fluxes (1997) [after H. Korth et al., 1999]

28. Kp-parameterization of convection Volland-Stern electric potential: Maynard and Chen (OGO 3,5) [JGR, p. 1009, 1975]:

29. Kp-Dependent Convection Geosynchronous Electron Fluxes (1997) [after H. Korth et al., 1999]

30. Kp-Dependent Convection Geosynchronous Electron Fluxes (1997) [after H. Korth et al., 1999]

31. Alfvén Boundaries => Upper Cutoff Energy Electron Alfven Energy (eV)

32. Electron Plasma Sheet Upper Cutoff Energy

33. Kp-Dependence of Upper Cutoff

34. Electron Plasma Sheet Upper Cutoff Energy convection enhancement

35. Bursty Convection Enhancements (Compare with direct E observations from CRRES and Polar: Wygant et al., 1998; Rowland and Wygant, 1998; Keiling et al., 2001)

36. Propagation of Convection Enhancements

38. What observations tell us about plasma-sheet losses Electrons Drift loss (“flow-through”) Precipitation Ions Drift loss Precipitation Charge exchange with exospheric neutrals

39. Plasma-Sheet Losses: Flow-Through

40. Plasma-Sheet Losses: Electron Precipitation (diffuse aurora)

41. Plasma-Sheet Losses: Charge-Exchange Proton Flux (10.6 keV) 1998 Kp After H. Korth et al., 2002

42. (T  h /T ||h ) - 1 n n /n e After Gary et al., JGR, 23603, 1994 increasing cold ion density Plasma-Sheet Losses: Ion Precipitation (proton aurora) Drainage Plume Hot ions drift through plume -> Enhanced precipitation?

43. Plasma Sheet Losses: Ion Precipitation Multiple-Satellite Observations 1991-080 1994-084 LANL-97A LANL-02A

44. Summary The plasma sheet is the source of dynamically important populations in the inner magnetosphere. It is highly variable, on widely different time scales, and its properties vary with geomagnetic activity. The solar wind is a likely source of plasma sheet material, possibly entering the magnetosphere via different mechanisms for northward and southward IMF. The ionosphere is also a likely source of plasma sheet material, especially at higher geomagnetic activity and F10.7. A combination of convection and gradient/curvature drift explains the gross morphology of the near-Earth plasma sheet surprisingly well. In practice the convection is rarely steady, apparently often delivering plasma- sheet material into the inner magnetosphere by bursts. The convection enhancements extend over several R e and propagate sunward from the near-midnight region. Once material is delivered to the inner magnetosphere, it is subject to losses by drift to the magnetopause, charge-exchange, and precipitation. Evidence for all these processes can be found at geosynchronous orbit.