Physics
Scientific paper
May 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm..sm22b09t&link_type=abstract
American Geophysical Union, Spring Meeting 2001, abstract #SM22B-09
Physics
2708 Current Systems (2409), 2730 Magnetosphere--Inner, 2740 Magnetospheric Configuration And Dynamics, 2753 Numerical Modeling
Scientific paper
This paper presents first results of an effort to develop an advanced model of the Earth's inner and near magnetosphere, based on large sets of spacecraft data and on new methods to represent the variable and complex geospace magnetic field structure. The model magnetopause size and shape are controlled by the solar wind pressure and the geodipole tilt angle. The magnetospheric field sources are represented by (i) symmetrical and partial ring currents, whose strength and size are functions of the corrected Dst-index, (ii) a flexible tilt-dependent cross-tail current sheet, parameterized by the solar wind pressure, IMF, and Dst, (iii) Region 1 and 2 Birkeland currents with a variable strength and geometry, depending on the solar wind input and the dipole tilt angle, and (iv) an IMF-controlled interconnection field, making it possible to model open magnetospheric configurations. The modeling database included 5-min average magnetospheric field data, taken in a wide range of altitudes and latitudes by the ISTP spacecraft POLAR (1996-99) and GEOTAIL (1994-99), as well as by earlier missions ISEE-1/2 (1984-87), AMPTE/CCE (1984-88), AMPTE/IRM (1984-86), CRRES (1990-91), and DE-1 (1984-90). In order to include in the model the effects of the delayed response of the magnetosphere to changes in the interplanetary medium, each data record was tagged by a "tail" of the 5-min average IMF, solar wind, and Dst-field data, covering a 2-hour interval, preceding a given magnetospheric observation. The solar wind and IMF data were provided by IMP 8 and WIND spacecraft, and the Dst-field data were compiled from a high-resolution SYM index of Kyoto WDC. First fitting runs yielded quite reasonable results, both in terms of the general response of the magnetospheric configuration to the external input, and with respect to variations of the individual field sources. In particular, the model revealed a significant increase of the partial ring current with growing ěrt Dstěrt, resulting in a strong duskside depression of B in the inner magnetosphere during storms. That fact was known from observations since long ago; however, none of the previous geomagnetic field models reproduced the dawn-dusk asymmetry. These results and challenges for the future data-based modeling studies will be discussed.
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