Solar-eclipse-induced perturbations at mid-latitude during the 21 August 2017 event

Abstract. A study of the response of some ionospheric parameters and their relationship in describing the behaviour of ionospheric mechanisms during the solar eclipse of 21 August 2017 is presented. Mid-latitude stations located along the eclipse path and with data available from the Global Ionospheric radio Observatory (GIRO) database were selected. The percentage of obscuration at these stations ranges between 63 % and 100 %. A decrease in electron density during the eclipse is attributed to a reduction in solar radiation and natural gas heating. The maximum magnitude of the eclipse consistently coincided with a hmF2 increase and with a lagged maximum decrease in NmF2 at the stations investigated. The results revealed that the horizontal neutral wind flow is as a consequence of the changes in the thermospheric and diffusion processes. The unusual increase and decrease in the shape and thickness parameters during the eclipse period relative to the control days points to the perturbation caused by the solar eclipse. The relationships of the bottomside ionosphere and the F2 layer parameters with respect to the scale height are shown in the present work as viable parameters for probing the topside ionosphere during the eclipse. Furthermore, this study shows that in addition to traditional ways of analysing the thermospheric composition and neutral wind flow, proper relation of standardized NmF2 and hmF2 can be conveniently used to describe the mechanisms.