HR: 10:55h
AN: SA12A-03 INVITED     [Abstracts]
TI: How the Ring Current Couples to the Radiation Belts and the Ionosphere
AU: * Brandt, P C
EM: pontus.brandt@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd. , Laurel, MD 20723 United States
AU: Zheng, Y
EM: yihua.zheng@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd. , Laurel, MD 20723 United States
AU: Ukhorskiy, A
EM: aleksandr.ukhorskiy@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd. , Laurel, MD 20723 United States
AU: Mitchell, D G
EM: donald.mitchell@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd. , Laurel, MD 20723 United States
AB: The plasma pressure in the ring current is associated with electrical currents that leads to global effects in the ionosphere/thermosphere and radiation belts. Two recent results of global data-model comparisons will be presented.

1. The ring current strongly affects the loss of radiation belt electrons. A single-particle code has been developed at The Johns Hopkins Unversity Applied Physics Laboratory (JHU/APL). It models the electron transport, conserving only the third adiabatic invariant, in a realistic, time-varying magnetic field. The Tsyganenko and Sitnov [2005] magnetic field model is used to compute the induction electric fields resulting from solar wind pressure variations. We find that during the mainphase of a geomagnetic storm, the strong local-time asymmetry of the magnetic field, due to the asymmetric partial ring current, together with the pressure-induced electric field fluctuations, lead to stochastic motion of MeV electrons in the vicinity of the magnetopause. The model shows that electrons around geosynchronous orbit are completely lost through the magnetopause due to this effect. We will investigate, solar wind, and radiation belt electron measurements together with global ring current data obtained by IMAGE/HENA in the mainphase of geomagnetic storms to find out if these model results are consistent with data.
2. The ring current and ionospheric conductance control the electric fields of the inner magnetopshere. Dawn-dusk penetration, or undershielding, electric fields occur in the ionosphere due to dawn-dusk interplanetary electric field (IEF) that increase faster than the ring current-ionosphere circuit has time to set up shielding electric fields. On the low-latitude dayside ionosphere, the resulting eastward electric fields can lift plasma and cause storm-enhanced densities (SED) in the F-region. In turn, when the SEDs are transported through Earth's rotation to the dusk terminator, the sub-auroral polarization stream (SAPS) electric field deviates the flow of SEDs poleward and sunward into narrow tongues of enhaced densities that correlate well with the location of the plasmaspheric plume. The Comprehensive Ring Current Model (CRCM) at JHU/APL reproduces both SAPS and undershielding electric fields. We will present some insights to the evolution and physics of the global sub-auroral electric fields by comparing model results with Ion Drift Meter (IDM) on board the Defense Meteorological Satellite Program (DMSP), IMAGE/HENA, IMAGE/EUV, SuperDARN, Millstone Hill, and Jicamarca radar data.
   DE: 2712 Electric fields (2411)
   DE: 2721 Field-aligned currents and current systems (2409)
   DE: 2730 Magnetosphere: inner
   DE: 2774 Radiation belts
   DE: 2778 Ring current
   SC: SPA-Aeronomy [SA]
   MN: Fall Meeting 2005