Solar Extreme Events of 2003:
Fundamental Science and Applied Aspects

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Geosynchronous magnetopause crossings and solar wind conditions on October 29-31, 2003
Suvorova A., Thomsen M., Skoug R., Dmitriev A., Chao J.-K.,

Comparative analysis of the solar wind conditions and magnetopause dynamics was performed for extremely disturbed event on October 29-31, 2003. It was found that ACE and Geotail upstream monitors provided very close data on the IMF, but plasma measurements on satellites SOHO, ACE and Geotail are very ambiguous. The solar wind velocity was estimated using time lag for propagation of such solar wind structures as interplanetary shock, Alfven waves and tangential discontinuities from point L1 to the Earth. The best correspondence of the velocity estimation was obtained with the ACE SWEPAM measurements, which displayed very fast (up to 2000 km/s) solar wind. Numerous geosynchronous magnetopause crossings (GMCs) were identified using magnetic field data from two GOES satellites and plasma data from four LANL satellites. We can distinguish 4 long-time intervals when several geosynchronous satellites observed magnetosheath intervals in a wide range of local time: ~6-9UT 29 October; from ~10UT 29 October to 4UT 30 October; from ~11UT 30 October to ~8UT 31 October; and 4) 11-14UT 31 October. The magnetopause dawn-dusk asymmetry was revealed on the main phase and in maximum of two great geomagnetic storms on October 29 and 30. The asymmetry can be represented as a shifting of the magnetopause toward the dusk on a distance of ~0.4 Re. Strong magnetospheric compression at 00-04 UT 30 October caused global magnetospheric pulsations with large amplitude estimated in the noon sector of about 0.26~0.6 Re. Extremely high solar wind pressure also caused numerous GMCs in the dawn and dusk sectors. Using magnetopause models we estimated the solar wind dynamic pressure required for the observed GMCs, that was revealed much larger than calculations from the plasma data of the upstream monitors. The understated values of the observed solar wind pressure was attributed to the solar wind density underestimation in the space plasma experiments under strongly disturbed solar wind conditions. The extremely high solar wind speed (more than 1000 km/s) and very intensive fluxes (more than 10 (cm2 s sr)-1) of high-energy solar energetic particles (>30 MeV protons) were considered as possible phenomena responsible for distortions in the experimental data the solar wind plasma parameters.

Skobeltsyn Institute of Nuclear Physics, Moscow State University, 2004