Dynamics of the auroral oval during geomagnetic disturbances observed by oblique sounding of the ionosphere in the Eurasian longitudinal sector

V. P. Uryadov and A. A. Ponyatov
Radiophysical Research Institute, Nizhny Novgorod, Russia

G. G. Vertogradov and V. G. Vertogradov
Rostov-on-Don State University, Rostov on Don, Russia

V. I. Kurkin and S. N. Ponomarchuk
Institute of Solar-Terrestrial Physics, Irkutsk, Russia

Abstract

[1]  Results of the experimental studies of features of HF signals propagation during the period of geomagnetic disturbances at oblique sounding paths in the Eurasian longitudinal sector from England to Magadan are presented. Joint analysis of the vertical and oblique sounding of the ionosphere and satellite data showed that appearance of additional signals during magnetic disturbances can be due to the refraction of radio waves in the region of the auroral oval and the main ionosphere trough and also to the scatter on small-scale field-aligned irregularities in the vicinity of the equatorial boundary of the auroral oval. On the basis of calculations and comparison to the experimental data of the oblique sounding of the midlatitude ionosphere, the side spread signals recorded at Inskip (England) to Rostov on Don path are identified as signals scattered at small-scale field-aligned irregularities, their location positioning to the southern boundary of the auroral oval. The perspective of use of the Russian and global network of linearly frequency modulated ionosondes for studying the dynamics of the midlatitude ionospheric trough and auroral oval in the Eurasian longitudinal sector poorly equipped by observational means during magnetic disturbances is described.

Received 27 July 2004; revised 14 April 2005; accepted 2 May 2005; published 20 September 2005.

Keywords: Electron collision frequency; Attenuation of HF radiowaves; Physics of the lower ionosphere.

Index Terms: 2407 Ionosphere: Auroral ionosphere; 2487 Ionosphere: Wave propagation; 2494 Ionosphere: Instruments and techniques.