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Global geomagnetic response to the sharp magnetosphere compression and IMF variations on October 29, 2003
Solovyev S.I., Moiseyev A.V., Mullayarov V.A., Du A., Engebretson M., Newitt L.R.,
Analysis results of the geomagnetic response during ~30 min after SC of the magnetic storm at 0611:30 UT on October 29, 2003 by using the global station chain are presented. The interaction of a shock with the Earth's magnetosphere is accompanied by the increase of the dynamic solar wind pressure (Pd) and by the rise of negative IMF Bz to ~-30 nT with the following change up to positive values ~+10 nT at 0617 UT. At the instant of the northward turning of the IMF Bz the sharp decrease of IMF By from +2 to -38 nT is observed. The comparison with VLF-emission data at Yakutsk (L=3.3) is shown that ~15 s before the positive preliminary impulse (PI) onset, detected almost in all time sectors and at all latitudes, the wide-band VLF-emission impulse is observed with the shift of the initial spectrum to higher frequencies. The estimation of the propagation Alfven's velocity of a hydromagnetic impulse at L less/equal 4 gives Va~880 km/s. The main impulse (MI) of SC during the first 5 min is characterized by the sharp intensification of the westward electrojet in the midnight-morning sector with maximum change of H-component of geomagnetic field equal to 2000 nT at latitudes 65-70 degs and the eastward electrojet in the postnoon sector with maximum change of H-component equal to 700 nT at latitudes less/equal 65 deg. The northward turning of IMF Bz led to the new global intensification of the westward electrojet including the postnoon sector at latitudes more/equal 70 deg. The expansion of the westward electrojet in the premidnight to the pole to latitudes ~80 deg with the velocity up to ~5 km/s and to the east with the velocity ~6-13 km/s. It is supposed that the geomagnetic response of electric currents to SC at the first 5 min is related to the rise of Pd, magnetospheric convection and DP2 current system strengthening. The following intensification of the westward electrojet and its expansion in azimuth is the result of IMF Bz and By variations and the MHD-wave generation. The work was supported by RFBR grant 03-05-39011-GFEN.