# Presentation: 358597

## The Geoeffectiveness of Solar Cycle 23 as inferred from a Physics-Based Storm Model 

- LWS Grant NAG5-13512
- _Principal Investigator:_
- Vania K. Jordanova
- Institute for the Study of Earth, Oceans, and Space Physics Department
- University of New Hampshire
- Goal: Investigate the effect of varying solar activity as reflected in near-Earth interplanetary conditions on energetic particle dynamics and how large geomagnetic storms form

## Working towards a realistic ring current model: High resolution electric field

- Proton ring current energy density in the equatorial plane during the main phase of the 10 January 1997 storm from our physics-based RAM model coupled with the two electric field models: (top) MACEP, and (bottom) Volland-Stern

**Working towards a realistic ring current model: High resolution electric field**

- Electric potentials during the 10 January 1997 storm mapped to the equatorial plane:
-   a) From the high resolution MACEP model we developed on the basis of the ionospheric AMIE model adding a penetration electric field (driven by partial ring current closure in the ionosphere)
-   b) From the Kp-dependent Volland-Stern model

## We studied the role of the spatial and temporal variability of the convection electric field on ring current development during the 10 January 1997 geomagnetic storm
  • we compared ring current simulations from our kinetic RAM model using (1) the Kp-dependent Volland-Stern model and (2) the high spatial and temporal resolution MACEP model; both electric field models predict strongest fields during the main phase of the storm, however:
	- Volland-Stern model is symmetric about dawn/dusk by definition 
	- MACEP model is more complex and exhibits variable east-west symmetry and spatial irregularities
  • although both convection models predicted a very asymmetric local time distribution of ring current energy density during the main and early recovery phase of the storm, its peak was located during the main phase near dusk using Volland-Stern model, while it was located near midnight when the MACEP model was used and in better agreement with recent ENA observations from IMAGE
  • in both models the energy density peak was located near dusk during the early recovery and the ring current became symmetric during the late recovery phase
  • ring current injection was larger, penetrating to lower L shells, and the Dst index significantly better reproduced using MACEP rather than using Volland-Stern model
  • we concluded that an inner magnetospheric electric field model with increased spatial and temporal specification during the main phase reproduced significantly better the ring current evolution during the January 1997 storm.
Future work: we will use the high resolution model to simulate ring current dynamics during the large geomagnetic storms of 31 March and 21 October 2001.

-   • we compared ring current simulations from our **kinetic RAM model** using (1) the Kp-dependent Volland-Stern model and (2) the high spatial and temporal resolution MACEP model; both electric field models predict strongest fields during the main phase of the storm, however:
- 	- **Volland-Stern** model is **symmetric** about dawn/dusk by definition
- 	- **MACEP** model is more **complex** and exhibits variable east-west symmetry and spatial irregularities
-   • although both convection models predicted a very asymmetric local time distribution of **ring current energy density** during the main and early recovery phase of the storm, its peak was located during the main phase near dusk using Volland-Stern model, while it was located near **midnight **when the **MACEP** model was used and in better agreement with recent ENA observations from IMAGE
-   • in both models the energy density peak was located near dusk during the early recovery and the ring current became symmetric during the late recovery phase
-   • ring current **injection** was larger, penetrating to lower L shells, and the **Dst **index significantly better reproduced using MACEP rather than using Volland-Stern model
-   • we concluded that an inner magnetospheric electric field model with increased spatial and temporal specification during the main phase **reproduced significantly better** the ring current evolution during the January 1997 storm.
- Future work: we will use the high resolution model to simulate ring current dynamics during the large geomagnetic storms of 31 March and 21 October 2001.

**Effects of Inner Magnetospheric Convection: ****January 10, 1997**

## Solar cycle variation of the radiation belts:Observations and radial diffusion simulation

- The 100 keV **electron flux** variations at **L=3** from NOAA observations (left) compared with simulations (right) :
- a) the 27-day averaged flux from 1979 to 2003; the dashed blue curve is the 13-month smoothed **solar F10.7 flux**
- b) the 27-day averaged flux from 1992 to 1995 when **semiannual** variations are apparent
- c) daily averaged electron fluxes during 1993 when **recurrent** variations with periods of both 13.5 and 27 days are apparent

-  A significant flux variation with solar cycle was detected even **deep in the inner magnetosphere**; the outer belt shifted **inward** during the **solar active **period and outward during the solar quiet period.
-  Although the numerical simulation overestimated the flux magnitude, it reproduced qualitatively the solar cycle and semiannual variations, and some recurrent variations of the **inner portion** of the outer belt, suggesting that radial diffusion is a major controlling parameter for the long-term variations.
-  The simulation did not reproduce the variation of the **outer portion** of the outer belt, suggesting further physical processes should be considered.