The ionospheric responses to the 11 August 1999 solar eclipse: observations and modeling

A total eclipse occurred on 11 August 1999 with its path of totality passing over central Europe in the latitude range 40–50 N. The ionospheric responses to this eclipse were measured by a wide ionosonde network. On the basis of the measurements of foE, foF1, and foF2 at sixteen ionosonde stations in Europe, we statistically analyze the variations of these parameters with a function of eclipse magnitude. To model the eclipse effects more accurately, a revised eclipse factor, FR , is constructed to describe the variations of solar radiation during the solar eclipse. Then we simulate the effect of this eclipse on the ionosphere with a midand low-latitude ionosphere theoretical model by using the revised eclipse factor during this eclipse. Simulations are highly consistent with the observations for the response in the E-region and F1-region. Both of them show that the maximum response of the mid-latitude ionosphere to the eclipse is found in the F1-region. Except the obvious ionospheric response at low altitudes below 500 km, calculations show that there is also a small response at high altitudes up to about 2000 km. In addition, calculations show that when the eclipse takes place in the Northern Hemisphere, a small ionospheric disturbance also appeared in the conjugate hemisphere.