Statistics – Computation
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufmsm41a0334t&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #SM41A-0334
Statistics
Computation
0500 Computational Geophysics (3200, 3252, 7833), 2730 Magnetosphere: Inner, 2740 Magnetospheric Configuration And Dynamics, 7954 Magnetic Storms (2788), 7959 Models
Scientific paper
Modeling the storm-time inner magnetosphere is central to space weather science. At the same time, it is particularly difficult using the first principle approaches because of significant non-MHD effects. A complementary approach may be data-based modeling, including empirical models of the magnetospheric magnetic field. Until recently these models were limited in their spatial resolution because they were constructed of a limited number of special modules representing major magnetospheric current systems. A new approach, based on a high- resolution extensible approximation for the field of equatorial currents and making use of large sets of spacecraft data that became available in recent years, is shown to dramatically improve the resolution of empirical geomagnetic field models [Tsyganenko and Sitnov, 2007]. However, increasing the spatial resolution may limit the resolution in time, because to get a good image one needs a long enough exposure, providing sufficiently dense coverage of the magnetosphere by the data points. We show that the problem can be resolved using the nearest-neighbor approach, in which the spatial structure of each new state of the magnetosphere is described by fitting the empirical model with a local subset of the basic set of data. This subset includes both the actual data available for the given state of the magnetosphere and data for other states (e.g., similar phases of other storms), neighboring the present state in the space of global parameters, such as Sym-H index, solar wind electric field, and their time derivatives. The new dynamical model reveals important spatio-temporal features of magnetospheric storms, such as the peak density of the ring current in the postmidnight sector during the main phase, consistent with IMAGE data [Brandt et al., 2002] and maximum depression of the equatorial magnetic field in the premidnight sector, consistent with earlier results [Ohtani et al., 2007]. It also predicts new effects, such as the strong erosion of the dayside part of the ring current at the early main phase and its enhancement near the Sym-H minimum in a broad area in the evening sector extending from the geostationary orbit to the magnetopause and adjacent to the plume region of the plasmasphere.
Sitnov Mikhail I.
Tsyganenko Nikolai A.
Ukhorskiy Aleksandr Y.
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