Ionospheric total electron content response to solar eclipses

Abstract

Abstract. On October 24, 1995, and March 9, 1997, two solar eclipse events occur. It is therefore of interest to investigate how the ionosphere responded to the eclipses. Five global positioning system (GPS) ground-based receivers are specifically designed to observe large-scale ionospheric variations over the geomagnetic equatorial, equatorial anomaly crest, and midlatitude regions. Two-dimensional images of ionospheric total electron content (TEC) during the two eclipse periods are constructed. The deviations in the TEC images on eclipse days from those on reference days show that during the eclipse days the ionosphere experienced some large-scale changes. Four features of the TEC deviations, pre-ascension (PA), major depression (MD), sunset ascension (SA), and secondary depression (SD) have been observed. A detailed study shows that in geomagnetic low latitudes, PAs are possibly related to the locations of the equatorial anomaly crest. The latitudinal location, amplitude, and occurrence time of MDs suggest that the fountain effect is essential. SAs and SDs occurring in geomagnetic equatorial and low latitudes and appearing respectively before/around and after local sunset indicate that the prereversal enhancement plays an important role.

Ionospheric response over Europe during the solar eclipse of March 20, 2015

“…5). The observed TEC depletion is higher than those reported earlier for the 1999 and 2005 eclipses by Jakowski et al ( , 2008 and also others (Tsai & Liu 1999;Rashid et al 2006). Jakowski et al (2008) found TEC reduction of up to several TEC units and the total plasma depletion of about 40% during the eclipse on August 11, 1999 and about 30% during the eclipse on October 3, 2005.…”

“…This explanation is only valid if the background ionosphere behaves regularly, i.e., external forces of non-eclipse origin can be ignored. In other cases, the delay times may range up to 120 min as reported by Tsai & Liu (1999) when studying the solar eclipses on October 24, 1995 and March 9, 1997 at low latitudes. Furthermore, Afraimovich et al (2002) reported very short response times of only a few minutes.…”

“…The observations indicate that a number of competitive processes are initiated by an eclipse often enhanced by dynamic forces associated with large-scale geophysical conditions not directly impacted by the solar eclipse. Thus, the ionospheric depletion signatures may be heavily disturbed by electrodynamic forces in equatorial regions (e.g., Cheng et al 1992;Tsai & Liu 1999) and by space weather effects, such as particle precipitation, at high latitudes (e.g., Rashid et al 2006;Pitout et al 2013). As reported by Chimonas & Hines (1970) and others, the rapidly moving cooling spot can act as a continuous source of travelling ionospheric disturbance (TID) like gravity waves (e.g., Liu et al 1998;Altadill et al 2001;Jakowski et al 2008).…”

“…However, gravity waves are only visible if the wave amplitude is large enough and the ray path geometry does not cancel out the wave signatures in the integral (Davis & Da Rosa 1970;Jakowski et al 1983Jakowski et al , 2001Tsai & Liu 1999;Rashid et al 2006). Moreover, the geomagnetic activity influences the generation mechanism of these TIDs.…”

Using the IRI, the MAGIC model, and the co-located ground-based GPS receivers to study ionospheric solar eclipse and storm signatures on July 22, 2009

“…Ionospheric eclipse observations make a worthwhile contribution to study transient properties due to decreasing in the ionizing radiation from the Sun. Scientists have been using the total electron content (TEC) derived from ground-based receivers of the global positioning system (GPS) to monitor the source-response relation between the ambient rates of production, chemical loss, and motion of ionization (see papers listed in Afraimovich et al, 1998;Tsai and Liu, 1999;Jakowski et al, 2002;Le et al, 2009).…”