Ionospheric Response to a Solar Eclipse in the Equatorial Anomaly Region

Abstract

On October 24, 1995 a solar eclipse occurred with its path of totality passing over southern Asia, but the associated region of its partial eclipse covered almost all of Asia.It was therefore of interest to investigate how the ionosphere responded to this eclipse, especially because the region in cluded the equatorial anomaly region.For this purpose the authors col lected and processed ionosonde data from six stations in the region.These data reveal three effects that are coherent geographically in that they cover at least two of these six stations: (1) For the region with geomagnetic lati tudes higher than 20 degrees, the N increased slightly immediately folmax lowing the first contact for about 30 minutes.(2) In response to the eclipse, the largest depression occurring roughly 1112 hours after the maximum obscuration was observed at approximately 14 degrees geomagnetic lati tude even though the percent obscuration of the Sun at latitudes lower than 14 degrees was larger.(3) Around 6 hours after the maximum phase an other secondary depression in the Nmax was observed for geomagnetic lati tudes lower than 14 degrees.Physical mechanisms that may be responsible for causing these effects are proposed and examined in this paper.They are all related to eclipse-caused dynamic effects.