Ionospheric observations of the solar eclipse on Oct. 24, 1995 at Chung-Li

The main purpose of this paper is to illustrate the usefulness of ionosonde observations in the study of the effects due to the transit of a solar eclipse. A sequence of ionograms were obtained during the eclipse on October 24, 1995 by the Chung-Li Digisonde (situated at 24.9°N, 121.5°E, 35.2°N magnetic dip). With fuzzy classification techniques being used, an algorithm was devised to automatically scale digital ionograms. In corresponding time, significant depletions of foE and foF1 were observed and were indicative of a response to the eclipse effect. Furthermore, a search for the production of atmospheric gravity waves (AGW) induced by the solar eclipse was investigated using the iso-frequency virtual height profiles with time. Time-frequency spectral analysis using the Wigner-Ville distribution was applied to obtain an AGW with a period of 18.5 min in the F1- and the lower part of the F2-layers. The induced AGW began at the start of the solar eclipse and ended a couple of hours after the completion of the eclipse. In contrast, the iso-frequency profiles with time were also spectrally analyzed with the maximum entropy method (MEM).