The equatorial ionospheric response over Tirunelveli to the 15 January 2010 annular solar eclipse: observations

Abstract

Abstract. In this paper we present a case study of the annular solar eclipse effects on the ionization of E and F regions of equatorial ionosphere over Tirunelveli [77.8 • E, 8.7 • N, dip 0.4 • N] by means of digital ionosonde on 15 January 2010. The maximum obscuration of the eclipse at this station was 84 % and it occurred in the afternoon. The E and F1 layers of the ionosphere showed very clear decrease in their electron concentrations, whereas the F2 layer did not show appreciable changes. A reduction of 30 % was observed in the foF1 during the maximum phase of the eclipse. During the beginning phase of the eclipse, an enhancement of 0.97 MHz was observed in the foF2 as compared to that of the control days. But the foF2 decreased gradually as the eclipse progressed and a decrease of 0.59 MHz was observed towards the end phase of the eclipse. Observed variations in the h F2 and hmF2 showed lower values than the control days, although hmF2 was found to increase a bit during the eclipse. Observed variability in the E, F1 and F2 layer ionospheric parameters on the eclipse day and their departure from the control days are discussed as the combined effect of annular eclipse and presence of counter equatorial electrojet (CEEJ).

Ionospheric vertical plasma drift and electron density response during total solar eclipses at equatorial/low latitude

“…The data from SPIDR are automatically scaled, and the data were validated for accuracy by comparing the diurnal morphology of the derived N m F 2 data from critical frequency (f o F 2 ) obtained from some of the stations under study against local time with the electron density profile at other stations [Chuo, 2013;Nayak et al, 2012;Adeniyi et al, 2007]. The results agree well with the known electron density profile.…”

“…Ionospheric response at low altitudes is governed mainly by photochemical processes so that the decrease of solar radiation during an eclipse is expected to decrease the electron production rate and hence the electron concentration [Nayak et al, 2012]. However, the F 2 layer behavior may be quite different as it is governed by photochemical processes as well as by electrodynamical and neutral forcing.…”

Ionospheric effects on the F region during the sunrise for the annular solar eclipse over Taiwan on 21 May 2012

“…The eclipse effect was larger at midday than in the morning and afternoon (Le et al, 2008Nayak et al, 2012), and high solar activity was more obvious than low solar activity (Nayak et al, 2012). In the present study, the event onset time was during the sunrise, and the F 1 and E layers were not formed during that period.…”

“…This was similarly observed in the temporal variation at the fixed frequency on the ground. The wave-like propagation could be triggered by the fast eastward-moving local neutral wind dynamo generated by a lower pressure system and the cold temperatures in the region of maximum obscuration (St. Maurice et al, 2011;Nayak et al, 2012).…”

“…By contrast, the F 2 layer remains ambiguous, showing various responses in various areas. Nayak et al (2012) studied the ionospheric response of the 15 January 2010 eclipse over an equatorial observation station, indicating that the electron density in the F 2 region decreased slightly, beginning at lower heights and extending to the layer peak at approximately noon. In addition, Jakowski et al (2008) studied the ionospheric behavior of the annular eclipse that occurred before noon on 3 October 2005 over Europe.…”