A comprehensive experimental study of the ionospheric response to the solar eclipse of March 9, 1997

We present the results of a comprehensive synchronous experimental study of the ionospheric response to the solar eclipse of March 9, 1997, by vertica l, oblique Doppler and oblique sounding in a region spanning similar to 80% of the eclipse lifetime (phi = 34-62 degrees N, lambda = 82-151 degrees E) . The Tomsk and Yakutsk ionospheric stations, as well as ELW-, LW-, MW-, an d SW-band radio paths of small, medium, and large lengths, were used. Durin g the solar eclipse, we revealed characteristic features of the behavior of the critical frequency and the lower boundary of the ionospheric F2 region , the effective heights at fixed plasma frequencies, as well as the Doppler frequency shift f(D) (MW-SW bands) and amplitude (ELW, LW, and SW bands) o f the signal. We show that the ionospheric relaxation time in the E-F regio ns is 6-17 min, and that the travel velocity of the lunar shadow is similar to0.7-1.0 km s(-1).