# Presentation: 177483

## Extracted from talks by Janet Kozyra, Don Carpenter, Dennis Gallagher, Bob Clauer, Mike Liemohn, Stanislav Sazykin, Bill Burke, Stefano Orsini, and Pontus Brandt

- SummaryGlobal Models and Data:  Focus on Inner Magnetosphere

## Ring Current Issues

**Kinetic RC models** consistently reproduce the general behavior of the Dst* index using semi-empirical electric field models and observed near-Earth plasma sheet source populations.  In most cases,  overpredict the contribution to Dst* due to total RC energy as a result of uncertainties in the electric field model and/or uncertainties in the contribution of field-aligned and closure currents to Dst*. Do not yet include RC self-field.  Other non-ring current contributions to Dst* must be secondary.
**New Predictions**:
- Main & early recovery phase RC is asymmetric and dominantly a partial RC loop.  Ions move on open drift paths to the magnetopause making only one pass through the inner magnetosphere.  Dominant loss is  through flow-out on the dayside.
- RC characteristics are rapidly influenced by changes in the inner plasma sheet populations and in the convection electric field strength directly transmitted along open drift paths.  Following consequences:

## Rapid (as low as 1 hour) loss time-scales during main phase due to “flow-out” which are correlated with VBs  in the solar wind (related to magnetospheric convection strength) 
Two-phase decay -- transition from fast “flow-out” loss to slower “charge-exchange loss” as open drift paths are converted to closed ones in the early recovery phase
Composition changes in the RC driven by composition changes in the inner plasma sheet in response to changing magnetic activity.  Produce close correlation between Dst and composition changes in the ring current.
Preconditioning:  Pre-existing RC populations from previous activity are largely swept out of the magnetosphere by new activity.  Preconditioning by prior activity may enter through driving of the plasma sheet (RC source population) characteristics
Direct Injection Source?  CRRES sees evidence for upflowing ions directly injected into the ring current region.  Not understood how this contributes to the ring current formation?  Need much more information on global distribution, persistence, composition, pitch angle and energy characteristics of these events.  Can global ENA images contribute to this issue?

**Two-phase decay** -- transition from fast “flow-out” loss to slower “charge-exchange loss” as open drift paths are converted to closed ones in the early recovery phase
**Composition changes in the RC** driven by composition changes in the inner plasma sheet in response to changing magnetic activity.  Produce close correlation between Dst and composition changes in the ring current.
**Preconditioning**:  Pre-existing RC populations from previous activity are largely swept out of the magnetosphere by new activity.  Preconditioning by prior activity may enter through driving of the plasma sheet (RC source population) characteristics
**Direct Injection Source?**  CRRES sees evidence for upflowing ions directly injected into the ring current region.  Not understood how this contributes to the ring current formation?  Need much more information on global distribution, persistence, composition, pitch angle and energy characteristics of these events.  Can global ENA images contribute to this issue?

## Ring Current Issues

- Rapid variations in the near-Earth plasma sheet density means that low-density flux tubes will be convected into the inner magnetosphere behind very high density flux tubes.  This creates a situation in MHD that is unstable to the interchange instability.  Preliminary RCM results indicate that this configuration is only borderline unstable.  It is stabilized to this point either by differential particle drifts or numerical diffusion in the model.  Further investigation is needed.  (Sazykin)

## Interpretation of Indices (Focus here on Dst)

- Many signatures contribute to Dst
- MLT-UT maps constructed with ~20 ground magnetometers show MLT-dependence of signatures in addition to global-averaged information contained in Dst index
- Show evidence of contributions of current systems responding to solar wind pressure hits -- not what one would expect from Chapman-Ferraro current system -- not removed by standard pressure corrections
- Observations indicate that immediate and dramatic enhancements in global DP2 current system in response to pressure hits overwhelms other contributions for several hours after pressure hit
- Large-scale substorms produce clear substorm current wedges at mid-latitudes.  Also associated with near in time ring current enhancements.  How do these signatures impact Dst? Clearly show asymmetry of ring current enhancements
- MLT-resolved information will refine our understanding of the meaning of the Dst index
- Important for real-time prediction and monitoring -- model verificaton -- data ingestion, etc.

## Coupling Processes

- The fundamental importance of the penetration electric field for the dynamical behavior of the ring current, thermal plasma and global ionosphere is becoming increasingly apparent.  It’s role in geoeffectiveness is not completely understood.
- Self-consistent magnetic field has important consequences.  Penetration fields persist for longer periods because stretched field configuration inhibits the re-establishment of shielding by the ring current. Not previously appreciated.  (Sazykin)
- New information (observations and models) indicates that the ring current is highly asymmetric and on dominantly on open drift paths during the main and recovery phase.  This implies a strong partial ring current loop with currents closing through the ionosphere.  Important to understand the details of the current closure.  New effort underway to combine AMIE specification of conductivities with FACs from ring current model to get realistic current closures

- Penetration electric fields

## This current closure (in combination with ionospheric conductivity gradients) results in strong and persistent  penetration electric fields.  DMSP observed up to 60 kV penetration potentials extending equatorward of the auroral electron boundary
Large portion of the penetration potential concentrated in small-scale structures called SAID events which create high-speed flow channels in the ionosphere.  Roughly a degree MLAT wide and a couple hours in MLT
Influence of penetration fields can extend all the way to the equatorial ionosphere on short time scales
Has global consequences to ionospheric stability -- triggers growth of equatorial bubles, related also to deep depletions ofequatorial F-region, etc.
Overshielding can develop near the inner edge of the ring current (seen on CRRES) -- effects on ionospheric potential have been observed on DMSP 
Changes in the global electric field potential pattern due to closure of the partial ring current through the ionosphere resemble statistically modified patterns demonstrated to create shoulders in the plasmaspheric distribution 

- Large portion of the penetration potential concentrated in small-scale structures called SAID events which create high-speed flow channels in the ionosphere.  Roughly a degree MLAT wide and a couple hours in MLT
- Influence of penetration fields can extend all the way to the equatorial ionosphere on short time scales
- Has global consequences to ionospheric stability -- triggers growth of equatorial bubles, related also to deep depletions ofequatorial F-region, etc.
- Overshielding can develop near the inner edge of the ring current (seen on CRRES) -- effects on ionospheric potential have been observed on DMSP
- Changes in the global electric field potential pattern due to closure of the partial ring current through the ionosphere resemble statistically modified patterns demonstrated to create shoulders in the plasmaspheric distribution

- Coupling Processes

- Penetration electric fields

## Plasmasphere Issues

- Reasons for variability in the plasmaspheric density structure are still not understood. Structuring is observed on all scale sizes down to L values as low as L~2
- Large and highly structured electric fields are also observed throughout these regions and are correlated with the presence of ring current ions.  Role of these fields in the structuring is not understood.
- Losses of plasmaspheric plasma to the underlying regions appear to occur and are also not understood.
- What is the dynamical behavior that forms density bite-outs (voids)?  How are they formed and why do they persist (some for up to 40 hours).
- Features already being observed in global images are:  corotating plasmaspheric shoulder, voids (density bite-outs). Have not seen detached plasma regions yet.
- How do induction fields from substorms modify this picture

## What new data shows & how it can be used to explore new issues -- Ring Current

- Can finer-scale structures (in the ring current?  in the plasmasphere?) indeed be resolved by global images?  Are other methods needed to observe and characterize smaller-scale structures and their dynamical behavior
- New statistical ring current models based upon AMPTE and CRRES show strong trapped component in the period preceeding an event.  This component disappears during main phase and is replaced by population on open drift paths.  In recovery, phase trapped component again dominates -- in agreement with model predictions
- New global observations with HENA show evidence of dayside outflow of ring current ions.  After northward turning of IMF, dayside population of ring current is re-established. -- outflow predicted by global ring current model for this event.
- Caution:  Pitch angle characteristics can dramatically impact which populations show up strongly in ENA images.  Highly trapped distributions show weaker signatures because remain in regions of low neutral density.  Mirroring particles produce strong ENA signatures.

## Time sequences of global images powerful tool for examing new dynamical issues:
conversion of asymmetric to symmetric ring current configurations -- conversion of open to closed drift trajectories -- how this relates to phases of the storm 
nature of flows of ring current ions to the dayside magnetopause and contribution to loss during the main phase
composition changes sweeping through the ring current region from the nightside plasma sheet as magnetic activity varies
interplay between substorm modification of the near-earth plasma sheet populations and enhanced convection in ring current build-up
To make progress on open issues need from global observations:
information on the global electric field pattern and its evolution  during events
MLT-resolved composition, energy and density of the near-Earth plasma sheet (ring current source population) and its variation during magnetic activity 

- conversion of asymmetric to symmetric ring current configurations -- conversion of open to closed drift trajectories -- how this relates to phases of the storm
- nature of flows of ring current ions to the dayside magnetopause and contribution to loss during the main phase
- composition changes sweeping through the ring current region from the nightside plasma sheet as magnetic activity varies
- interplay between substorm modification of the near-earth plasma sheet populations and enhanced convection in ring current build-up
- To make progress on open issues need from global observations:
- information on the global electric field pattern and its evolution  during events
- MLT-resolved composition, energy and density of the near-Earth plasma sheet (ring current source population) and its variation during magnetic activity

- What new data shows & how it can be used to explore new issues -- Ring Current

## Information on global distribution of ionospheric populations directly injection into the ring current region
Evolution of global plasmaspheric configuration including small-scale density structures (to specify environment for plasma waves, Coulomb losses, etc.)
Contributions of Global Models
Enable interpretation of physical processes driving the observed global dynamics
Supply initial guess to support
ENA inversion (especially related to small-scale structures)
Estimation of global electric field evolution from global images

- Evolution of global plasmaspheric configuration including small-scale density structures (to specify environment for plasma waves, Coulomb losses, etc.)
- Contributions of Global Models
- Enable interpretation of physical processes driving the observed global dynamics
- Supply initial guess to support
- ENA inversion (especially related to small-scale structures)
- Estimation of global electric field evolution from global images

- What new data shows & how it can be used to explore new issues -- Ring Current

## Much can be added to the observational picture and many questions answered by global images which show the longitudinal extent of plasmaspheric structures, their dynamic behavior and their relationship to other elements (like the ring current, global electric field pattern, etc.).
New features and their dynamical behavior being identified in the global images already.  
  shoulder in plasmaspheric boundary that corotates following formation.  Preliminary results indicate it may be related to a transient feature in the global electric field pattern (resembling that produced by the ring current penetration electric field)
Evidence for finger-type structures, voids is density
Clear that need to understand more about 
plasmasphere-ring current  interactions 
plasmasphere - superthermal electron interactions
consequences for ionospheric sources and losses

- New features and their dynamical behavior being identified in the global images already.
-   shoulder in plasmaspheric boundary that corotates following formation.  Preliminary results indicate it may be related to a transient feature in the global electric field pattern (resembling that produced by the ring current penetration electric field)
- Evidence for finger-type structures, voids is density
- Clear that need to understand more about
- plasmasphere-ring current  interactions
- plasmasphere - superthermal electron interactions
- consequences for ionospheric sources and losses

- What new data shows & how it can be used to explore new issues:  Plasmasphere

## What new data shows & how it can be used to explore new issues:  Global Electric Fields

- RCM contributed much to our understanding of penetration electric fields -- recently validated extensively by comparing DMSP potentials and CRRES observations against the model results in the magnetosphere and underlying ionosphere for the June 1991 storm interval -- uses statistical patterns of conductivity and for RC source populations  -- need to test understanding against observations that are more represenatitve of selected events
- Preliminary investigations using AMIE specifications of the conductivity and calculated field-aligned currents from a data-driven ring current model show interesting features
- In particular, can these models reproduce the small-scale and intense features (SAIDs) that are superposed on the larger-scale and weaker penetration electric fields

**GLOBAL ELECTRIC FIELD (including PENETRATION FIELD)**

## How do these more complex global convection patterns impact the location in MLT and extent of open drift paths from the magnetotail that supply the ring current source population during storms.   There are MLT-dependent populations observed at geosynchronous orbit with differing energy, composition and density characteristics which may have interesting impacts on the ring current formation
Can global imaging sequences of plasmasphere and/or ring current provide information on the penetration fields from their impact on the global configuration of the plasmasphere and ring current? 
ENA images through determination of the average energy of the ring current versus local time may be able to provide an estimate of the potential drop in the cross-tail field.  Work continues on this.

- Can global imaging sequences of plasmasphere and/or ring current provide information on the penetration fields from their impact on the global configuration of the plasmasphere and ring current?
- ENA images through determination of the average energy of the ring current versus local time may be able to provide an estimate of the potential drop in the cross-tail field.  Work continues on this.

- What new data shows & how it can be used to explore new issues:  Global Electric Fields