Height Dependency of Solar Eclipse Effects: The Ionospheric Perspective

Abstract

AbstractA reliable interpretation of solar eclipse effects on the geospace environment, and on the ionosphere in particular, necessitates a careful consideration of the so‐called eclipse geometry. A solar eclipse is a relatively rare astronomical phenomenon, which geometry is rather complex, specific for each event, and fast changing in time. The standard, most popular way to look at the eclipse geometry is via the two‐dimensional representation (map) of the solar obscuration on the Earth's surface, in which the path of eclipse totality is drawn together with isolines of the gradually‐decreasing eclipse magnitude farther away from this path. Such “surface maps” are widely used to readily explain some of the solar eclipse effects including, for example, the well‐known decrease in total ionization (due to the substantial decrease in solar irradiation), usually presented by the popular and easy to understand ionospheric characteristic of total electron content (TEC). However, many other effects, especially those taking place at higher altitudes, cannot be explained in this fashion. Instead, a more detailed description of the umbra (and penumbra), would be required. This paper addresses the issue of eclipse geometry effects on various ionospheric observations carried out during the total solar eclipse of 21 August 2017. In particular, GPS‐based TEC measurements were analyzed and eclipse effects on the ionosphere are interpreted with respect to the actual eclipse geometry at ionospheric heights. Whenever possible, a comparison was made with results from other eclipse events.