1. Ring Current and Plasmasphere Accomplishments During the GEM IM/S Campaign Mike Liemohn GEM Workshop Tutorial June 27, 2006

2. IM/S Campaign: Outcomes and Questions How well do we understand the physics of the inner magnetosphere? –What are the physical questions remaining to understand the inner magnetosphere? –How far have we come since the beginning of the IM/S Campaign (1998)? What advances in observations are needed next? –Of these, which can be anticipated in current plans? –Which observations can be readily achieved, which are dependent on advances in experimental physics, and which cannot be currently foreseen as possible? What advances in modeling are needed next? –Are there important physical processes that are not yet included? –Can regional models be advanced independent of system-wide modeling? –What advances in numerical technique and processing power are needed?

3. Basic Definition: Plasmasphere Cold: Less than 1 eV, maybe up to 10 eV Dense: 100s-1000s cm -3, lower out near geos. Ionospheric: source is the subauroral ionosphere Mostly Protons: oft-quoted composition, 77% H +, 20% He +, and 3% O + E-field dominated: spatial extent governed by magnetospheric electric field time history Important: dominates the mass density of the inner magnetosphere

4. Basic Definition: Ring Current Hot: 1-400 keV Tenuous: quiet, 1 cm -3 ; active, 10s cm -3 Plasma sheet: source is near-Earth magnetotail, wherever that comes from Mostly Protons: During big storms, O + can dominate Complicated Drift: E-field, B-field, Gradient- curvature terms Important: Dominates the energy density of the inner magnetosphere

5. Ring Current Advances Storm-Time Ring Current Morphology –Partial ring current dominance during storms Connection/Feedback with Electric Field –The ionosphere matters Connection/Feedback with Magnetic Field –The B-field really is tweaked by currents Connection/Feedback with Plasma Sheet –Has anyone seen my source term? Connection/Feedback with Plasma Waves –Collisionless energy transfer

6. Ring Current Morphology The ring current is not a ring during storms Liemohn et al., JGR, 2001 From Don Mitchell

7. Ring Current-FAC-  Relationship A pressure peak requires FACs at each end to close the partial ring current, and the resulting potentials act to expel the pressure peak Liemohn and Brandt,AGU Mon v. 159, 2005

8. Electric Field Connection Partial ring current causes a potential well near midnight, changing the hot ion drift paths in the inner magnetosphere 8 UT 12 August 2000 Post- midnight enhance- ment Fok et al., SSR, 2003

9. Electric Field, Part 2: SAPS and Flow Channels SAPS: subauroral polarization stream –Enhanced outward E-field in dusk/evening sector causing faster-than-normal sunward flow Flow channels: narrow regions of injection –Enhanced westward E-field in localized sector of nightside causing fast injection Foster and Vo, JGR, 2002 Chen et al., JGR, 2003

10. Ganushkina et al., JGR, 2006 Magnetic Field Connection One-way connection: B- field influences on the ring current –Trends in the ring current energy content time series are best reproduced when B is stretched realistically and when convective & inductive E-fields are included Particle Tracing Model With Inductive-E Pulses

11. Zaharia et al., JGR, 2005 Magnetic Fields: 2-Way Coupling B-field found from RC result, then fed back to RC model Pressure (P  ) overall significantly smaller (half) in self-consistent (SC) case vs. dipole field; P || (not shown) not as affected Less plasma delivered close to Earth, but more structure Less filled flux tubes are able to drift closer to Earth

12. The Flip Side of Feeback: Effect of the Hot Ions on B X-Y plane pressures with 3-d B lines for a given latitude overdrawn Tail stretching –Pressure much higher near the Earth with kinetic code embedded –Hot ions near Earth alter the field and plasma in other areas With Kinetic CodeWithout Kinetic Code From Toth, Ridley, and De Zeeuw

13. Ebihara & Ejiri, JGR, 2000Liemohn and Ridley, JGR 2002 Plasma Sheet Connection Plasma sheet density controls the strength of the ring current Plasma sheet temperature also affects ring current intensity

14. Plasma Wave Connection Calculating the EMIC wave energy density self- consistently with the hot ions allows for nonlinear feedback between them –Scattering of ions depends on B w and  –Preference for field-aligned  Also a heat source for the thermal plasma Khazanov et al., JGR, 2006

15. What is Needed for Improvement Major Modeling Needs: –More fully develop self-consistency in the models –Continue to couple ring current models to other inner magnetospheric models and to global models –Better electron ring current loss lifetimes/diffusion coefficients –Algorithms for accurate hot plasma precipitation calculation Major Observational Needs: –Routine ion composition measurements at GEO –More reliable electron ring current measurements –Multi-spacecraft particle, field, and wave measurements in the ring current region –More/better ionospheric conductance measurements

16. Plasmasphere Advances Global Morphology –The plasmapause is lumpy, and we know why Magnetic Field Effects –The plasmasphere is more than just an E-field history integrator Plasmaspheric Refilling –Diffusive equilibrium is not quite right Mass Density –ULF wave analysis comes of age

17. Global Morphology IMAGE EUV has shown the plasmasphere to be a lumpy and bumpy creature –Tracer of the time-history of inner mag. fields (mostly E, also B) Sandel et al., SSR, 2003

18. Plasmapause and the E-Field Electric field choice can greatly influence the shape and dynamics of the plasmapause Liemohn et al., JGR, 2004

19. Slide from Stan Sazykin, Rice U. Plasmapause and The B-Field Comparison of the RCM-computed plasmapause boundary –Magnetic Field: HV95 (left panel) and T03S (right panel) –Plasmasphere is orange, filled at start of simulation –Contour lines: flow lines for cold ( =0) particles –EUV-extracted plasmapause: blue symbols in each plot Hilmer-Voigt B-FieldT03s B-Field

20. Plasmaspheric Refilling Variable refilling rates –Slow-then-fast refilling –Different processes –Lawrence et al., JGR, 1999 Field-line distributions –Flat at the equator –Does not follow diffusive equilibrium –Reinisch et al., JGR, 2004

21. Plasmaspheric Mass Density Ground-based magnetometers and field-aligned wave propagation –Multiple stations can be used to extract mass density along a field line –These results: from the MEASURE mag chain Berube et al., GRL, 2005

22. Magnetoseismology Probing the mass density of the magnetosphere via plasma wave transit times Chi and Russell, GRL, 2005

23. What is Needed for Improvement Major Modeling Needs: –Inclusion of heavy ion species –Inclusion of temperature calculation –Better coupling with ring current and ionosphere –Inclusion in global models –Small-scale structure, subcorotation, and refilling still not well understood Major Observational Needs: –Routine derivation of TEC from LEO –Refinement of ULF-wave data analysis techniques –Establish global ground and space operational systems for making coordinated observations in time and space –Follow-on IMAGE-type suite of instruments

24. Ring Current Dynamics Role of Plasma Sheet Source Population Role of Driving E and B Fields Role of Loss Mechanisms Morphology of Storm Quantification of Interdependencies?

25. Plasmasphere Dynamics Subauroral Electric Fields on All Scales Storm-time Sources: Composition & Latitude & Longitude Losses Internal and External to Storm-Time Plasmapause Morphology of Storm Origin of Plasmaspheric Structures at all Scales?

26. Inner Magnetospheric Coupling: Ring Current and Plasmasphere Ring Current E and B Fields Plasmasphere Localized IM perturb. J , J || Heating Localized IM perturb. Conductivity Collisions, WPI catalyst

27. Inner Magnetospheric Coupling Ring Current Localized E and B Field Pertubations Plasmasphere Conductivity Collisions, WPI catalyst  E and  B Heating Radiation Belts Precip, J , J ||  E and  B Diagnostic tracers Precip. WPI catalyst BB Diagnostic tracers Plasma Waves, Seed Pop. Ionospheric Conductance and Dynamics Ionospheri c Outflow Plasma Sheet ULF Waves Large Scale E and B Fields Liemohn, JGR, 2006

28. A Complicated Flow Chart Liemohn and Khazanov, AGU Mon. 156, 2005

29. Culmination of the IM/S Campaign The Inner Magnetosphere/Storms Assessment Challenge (the IMSAC) –The final hurrah of the IM/S Campaign –Focus the community's efforts on a common goal –Choose a few specific events for intense study –Choose a few questions to direct the investigations

30. Purpose of the IMSAC Goal 1: To what accuracy can the current inner magnetospheric models predict the state of the fields and plasma? –Related question: What level of model sophistication is needed to get a certain level of accuracy in the result? Goal 2: What is the present consensus understanding of inner magnetospheric physics? –Related question: What is the full set of physics for a complete description?

31. Storm Selection Two storms for the plasmasphere and ring current: –April 22, 2001: cloud with southward IMF –October 21-23, 2001: sheath/cloud combo Two storms for the radiation belts: –October 21-23, 2001: large storm followed by a large RB enhancement –September 4-9, 2002: a series of storms with interestnig RB dynamics

32. Culmination of the IMSAC JGR-Space Special Section –Submission deadline was January 9th –17 manuscripts submitted Some in print/press, most still in review/revision Over half focused on ring current dynamics Please, keep submitting papers –Additional papers can still be linked to the special section in the online listing

33. Conclusions GEM IM/S Campaign was a success! –Focused community effort on plasmasphere and ring current issues –Understanding of magnetic storms is much better now –New questions are plentiful Still to do –Coupling processes between plasma populations –Self-consistent simulations still need improvement –Coupling to sub-auroral ionosphere –Coupling to outer magnetosphere –Understanding small-scale plasma/field structures