Impact of the 15 January 2010 annular solar eclipse on the equatorial and low latitude ionosphere over the Indian region

Abstract

a b s t r a c tThe annular solar eclipse of 15 January 2010 over southern India was studied with a multi-instrument network consisting of magnetometer, ionosonde and GPS receivers. The presence of a counter electrojet (weakened or westward zonal electric field) during the eclipse and adjacent days suggests the strong gravitational tidal effect associated with the exceptional Sun-Moon-Earth alignment around the eclipse day. With a strong backup of magnetometer recordings on the day of eclipse, its adjacent days and the normal electrojet day, it is argued that the regular eastward electric field for the whole day at the equator was not just weakened, but actually was flipped for several hours by the influence of enhanced lunar tides. The effect of flipping the electric field was clearly seen in the equatorial ionosonde data and through the large array of GPS receivers that produced the total electron content (TEC) data. The main impact of flipping the electric field was poor feeding of equatorial ionization anomaly (EIA) due to the severely weakened fountain effect on the eclipse day, with the regular anomaly crest shifting towards the equator. The equatorial ionosonde profile was also showing an enhanced F2 region peak in spite of a reduced vertical TEC. While the plasma density depletion at the lower F region altitude over the equator was due to the temporary lack of photo-ionization, the reductions in high altitude plasma density beyond the equator were caused by the electrodynamics taking place around the eclipse. The important finding of this analysis is that the electrodynamical consequences on the low latitude ionosphere were mainly due to the combination of eclipse and lunar tides which were far more significant and influenced the EIA density rather than eclipse alone. Based on these findings, it is argued that the prevailing lunar tidal impact also needs to be taken into account while seeking to understand the electrodynamical impact of the solar eclipse on the low latitude ionosphere.

Ionospheric Effects During the Total Solar Eclipse Over Southeast Asia‐Pacific on 9 March 2016: Part 1. Vertical Movement of Plasma Layer and Reduction in Electron Plasma Density

“…Such equatorial fountain disruption can happen if a strong westward electric field develops at the geomagnetic equator, which might be a realistic possibility considering a number of past solar eclipse studies that have reported cases of counter‐electrojet current when the eclipse totality trajectory traversed over the geomagnetic equator (e.g. Cheng et al, ; Panda et al, ; St.‐Maurice et al, ; Tomas et al, , ; Vyas & Sunda, ). The presence of westward electric field along the wake of the eclipse totality would also be consistent with the downward ionospheric drift velocity observed on 9 March 2016 over Guam during the last half of the solar eclipse (cf.…”

Signatures of Equatorial Plasma Bubbles and Ionospheric Scintillations from Magnetometer and GNSS Observations in the Indian Longitudes during the Space Weather Events of Early September 2017

“…The proxy equatorial electrojet (EEJ) strength to the EEJ current in the ionospheric E-layer was calculated by subtracting the local midnight baseline values from the magnetometer H variation at equatorial TIR and the off-equatorial ABG observatory, and then finding the difference between them, as shown in Equation (1). This approach was previously proposed by Nair et al [53], and thereafter used by many researchers as a proxy to understand the characteristics of transmitted fields and the state of the equatorial ionosphere, especially during the daytime [2,54,55].…”

Coordinated Ground‐Based and Space‐Borne Observations of Ionospheric Response to the Annular Solar Eclipse on 26 December 2019

“…Several studies have indicated that an eclipse could induce rapid motion of low-pressure systems and cause significant wind convergence, triggering a local neutral wind dynamo that flows in a direction opposite to the normal daytime solar quiet (SQ) current system, and this feature has been termed a counter-SQ current pattern (Choudhary et al, 2011;St.-Maurice et al, 2011). Under these conditions, when the low-pressure system center (maximum obscuration) approaches the magnetic equator, the equatorial electrojet (EEJ) will be largely weakened and sometimes even a full-blown counter electrojet (CEJ) could be developed after the pass of maximum obscuration, a signature that fundamentally depends on competition between local and global dynamos (Cheng et al, 1992;Panda et al, 2015;Tomás et al, 2007Tomás et al, , 2008Vyas & Sunda, 2012). In the December 2019 eclipse event under study, the annular eclipse center crossed the magnetic equator in the early morning over Indian sector (see Figure 8a).…”