HR: 14:00h
AN: SM23D-01 INVITED     [Abstracts]
TI: Storm-time Distortion of the Near Magnetosphere as Revealed by Data-Based Models
AU: * Sitnov, M I
EM: sitnov@umd.edu
AF: Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742-3511, United States
AU: Tsyganenko, N A
EM: Nikolai.Tsyganenko@gsfc.nasa.gov
AF: Universities Space Research Association, Code 674, Space Weather Laboratory, NASA Goggard Space Flight Center, Greenbelt, MD 20771, United States
AB: An overview will be given of recent progress in the empirical modeling of the geomagnetic field, focused on the storm-time reconfiguration of the inner magnetosphere. Data-based modeling still remains one of primary techniques for representing and forecasting the structure and dynamics of the inner magnetosphere, an extremely hard task for the first-principle approaches. The storm-time evolution of the inner geomagnetic field was quantitatively modeled by Tsyganenko, Singer, and Kasper [2003], where it was shown for the first time that a global dramatic distortion of the magnetic field during strong storms could penetrate as deep as to only R ~ 3R_E. The dynamical aspects of storm-time magnetic field distortions were further elaborated in the TS05 model [Tsyganenko and Sitnov, 2005]. It was shown, in particular, that the magnetospheric response to the solar wind loading is drastically different for major current systems (ring, tail, and field-aligned currents), with the fastest response for field-aligned currents and the slowest for the symmetrical ring current. Finally, to resolve the complex spatial structure of storm-time magnetic field distortions Tsyganenko and Sitnov [2007] elaborated a new model with a high-resolution extensible approximation for the field of equatorial currents combined with a flexible field-aligned current module. The new model was fitted to a new database of space magnetometer data from Geotail, Polar, Cluster, IMP-8, and Goes-8,-9,-10, and -12, as well as concurrent solar wind and IMF data, spanning more than a decade (1995-2005). The new high-resolution magnetic field modeling revealed many interesting effects that were conjectured earlier based on other (largely indirect) methods, such as the pile-up of the magnetic flux near the magnetopause for northward IMF and the strong erosion/depression of the dayside field during intervals of southward IMF. It also revealed a dramatic difference between the global configurations of equatorial electric current systems at different phases of a storm. During the main phase, the current distribution has an interesting, highly deformed ‘hook-like' shape, which has virtually nothing to do with a traditional notion of a closed ring current. In contrast, at the recovery phase the model reveals an almost completely axisymmetric smooth pattern, without any distinct boundary between the ring and tail currents. We will also discuss the use of the empirical dynamical models of the geomagnetic field for calculations of the inductive storm-time electric fields in the inner magnetosphere [Ukhorskiy et al., 2006].
DE: 2740 Magnetospheric configuration and dynamics
DE: 2744 Magnetotail
DE: 2753 Numerical modeling
DE: 2788 Magnetic storms and substorms (7954)
DE: 2794 Instruments and techniques
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly