EFFECT OF THE SOLAR ECLIPSE OF 22 JULY 1990 AT MIDLATITUDE PATH OF HFPROPAGATION

Observational results obtained during the solar eclipse of 22 July 199 0 using the oblique sounding method for a midlatitude, Irkutsk to Nizh ny Novgorod path are presented. A chirp sounder with high time delay a nd frequency resolution was used in the measurements. The electron den sity profile for the mid-point of the path was restored using the redu ction method. It is shown that, during the solar eclipse with maximum obscuration similar to 70%, the electron density in the F-region decre ased by 6-8% compared with control day values. Travelling ionospheric disturbances caused by the eclipse-generated acoustic gravity waves we re detected. Strong variations in the difference group delays (Delta t au) between the high-angle and low-angle rays with a period similar to 40 minutes associated with the start and end of the eclipse, were fou nd. The vertical component of the disturbance speed determined from th e time delay oscillation, Delta tau, relative to the eclipse start for the ozone layer (near an altitude of 45 km) of the sub-ionospheric po int for the 1F2 mode reflection reaches a value similar to 230 m/s. (C ) 1998 Elsevier Science Ltd. All rights reserved.