Extreme solar events and magnetic storms in October 2003 and...

1. Introduction

Figure 1

[2] Extreme development of solar processes at the end of October 2003 led to prominent magnetic storms on 29 and 30 October. Anomalous speeds of the solar wind reaching 2000 km s ^-1 were registered in this period. The value of the B_z component in some moments was -(40-50) nT. The estimates of the electric field of the solar wind showed that its magnitude also reached extreme values up to 40-50 mV m ^-1 [see, e.g., Panasyuk et al., 2004]. The extreme development of the processes on the Sun at the end of October 2003 and the further extreme development of auroral and geomagnetic disturbances led to a principal changes in the structure and dynamics of the magnetosphere and ionosphere in this period [Ivanov et al., 2005; Lopez et al., 2004; Panasyuk et al., 2004; Veselovsky et al., 2004; Webb and Allen, 2004; Woods et al., 2004; Zherebtsov et al., 2005]. The disturbances were covering the entire thickness of the ionosphere. The auroral processes typical for high latitudes shifted to middle latitudes where only limited experimental means for observation of auroral processes are available. Analysis of VLF signals is one of the methods of observations of disturbances at middle latitudes in the considered period of time. The VLF signal characteristics are very sensitive to variations in the ionospheric D region [see, e.g., Rishbeth and Garriott, 1969]. Therefore studies of the changes in VLF propagation conditions at space separated midlatitude paths (see Figure 1) provide a possibility to study the development of ionosphere-magnetosphere disturbances including the regions of injection of charged particle fluxes into the ionosphere in the regions where there is no means for registration of auroral events.

[3] The goal of this paper is studying of the variability of the electron concentration in the ionospheric D region after the solar flares on 28 and 29 October 2003 and the following development of magnetic storms on 29 and 30 October 2003 and also analysis of the shifts and dynamics of the boundaries of charged particle precipitation regions.