7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Ionospheric total electron content variation along the annularity path during
June 21, 2020, annular solar eclipse
1Ajeet K Maurya
Department of physics, Babasaheb Bhimrao Ambedkar University, Lucknow Indiae-mail (speaker): ajeet.iig@gmail.com

Solar eclipses are being studied since several decade but
still considered an important event due to theiruniqueness to understand several unknown problems
related to the radio wave propagation and ionosphericvariation in the sudden absence of ionizing radiation. In
this paper we focused on the low and equatorial latitude
ionospheric response to the annular eclipse of 21 June
2021. The eclipse took place on the day of the Junesolstice and covering long path starting from Africa to
Asia with maximum eclipse over Indian region. The
special focused in this work is to understand local timedependence of solar eclipse effect along the annularity
path, which is not studied earlier. The analysis followed
ground based and space born global navigational satellite
system (GNSS) derived total electron content (TEC) dataof the 06 International GNSS service (IGS) stations, 06
GNSS stations operated by IIRS, ISRO, India,
FORMOSAT-7/COSMIC-2 (F7/C2) data and Global
Ionosphere Maps (GIMs) data, which were utilized
during the eclipse. The main focus to understand TEC
along annularity path, thus entire path divided on four
major regions: Africa, Arab, India and Taiwan. Over theAfrica and Arab regions eclipse occurred during earlymorning time, over Indian region eclipse happened
during noon time, while over Taiwan region, it was lateafternoon or evening local time. The GNSS station lying
nearly same eclipse magnitude/obscuration are chosen in
the current work. In order to understand dynamicalvariation of eclipse, two PRNs 06 & 19 covering eclipse
duration were analyzed. The average change in VTEC oneclipse day with reference to the normal days, for both
PRNs during three different time of the day, varies as~4.5-1.5 TECu during morning (Africa & Arab),~4.5-1.5 TECu (India) during noon time, and~7.5-3TECu during evening time (Taiwan). For thosestations, where PRN06 pass close to maximum eclipse, it
dominates over PRN19.

The change in the vertical electron density profile asobtained from COSMIC-2 profile showed significant
decrease over the altitude range of 100-350km, withmaximum decrease over Taiwan region (~40%), whileclosely similar decrease over Africa, and minimum
decrease over Indian region. Further, the TEC variation
using GIM maps showed maximum change (in terms ofnegative anomaly) over Africa and Taiwan region,
whereas over Indian region less negative anomaly
reported. All three methods, showed maximum decreaseover Taiwan region similar to the previous reports on thesame eclipse, but intriguing result in this work is slightly
similar decrease over Africa region during morning time.
We suggest effect of background density, eclipse inducechange in photo-chemical process and eclipse inducedchange in equatorial fountain effect collectively
producing considerably TEC reduction during morning
time as seen in the present case.

References[1] Aa, E., Zhang, S.-R., Erickson, P. J.,Goncharenko, L.
P., Coster, A. J.,Jonah, O. F., et al. (2020). Coordinatedground-based and space-borne observations ofionospheric response to the annular solar eclipse on 26
December 2019, Journal of Geophysical Research: Space
Physics,125,e2020JA028296.
https://doi.org/10.1029/2020JA028296[2] Huang, F., Li, Q., Shen, X., Xiong, C., Yan, R., hang,
S.‐R., et al. (2020). Ionospheric responses at low
latitudes to the annular solar eclipse on 21 June 2020,
Journal of Geophysical Research: Space Physics, 125,e2020JA028483, https://doi.org/10.1029/2020JA02848