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

Abstract

This paper studies the ionosphere's response to the annular solar eclipse on 26 December 2019, utilizing the following ground-based and space-borne measurements: Global Navigation Satellite System (GNSS) total electron content (TEC) data, spectral radiance data from the Sentinel-5P satellite, in situ electron density and/or temperature measurements from DMSP and Swarm satellites, and local magnetometer data. Analysis concentrated on ionospheric effects over low-latitude regions with respect to obscuration, local time, latitude, and altitude. The main results are as follows: (1) a local TEC reduction of ∼4-6 TECU (30-50%) was identified along the annular eclipse path, with larger depletion and longer recovery periods in the morning eclipse compared to midday. (2) The equatorial electrojet current was significantly weakened when the eclipse trajectory crossed the magnetic equator in the morning (India) sector, which contributed to large and prolonged TEC depletion therein. (3) At midday, equatorial ionization anomaly exhibited enhancements of 20-40% as well as poleward shifting of 3-4 • , likely triggered by modified neutral wind and electrodynamics patterns. (4) The behavior of equatorial ionospheric electron density showed considerable altitudinal differences in the topside, exhibiting ∼30% reduction around 500 km and ∼30% enhancement with 300-500 K Te reduction around 850 km, before the arrival of maximum eclipse. This may have been caused by the enhanced eastward electric field and equatorward neutral wind, and other possible factors are also discussed.

Ionosonde and GPS Total Electron Content Observations during the 26 December 2019 Annular Solar Eclipse over Indonesia

“…As a result of this siphoning, the area north of the eclipse trajectory was left with a greater deficit in TEC. Such a role of the fountain effect during a solar eclipse over low-latitude region is consistent with findings reported by Aa et al (2020).…”

“…The foF2 overshoot had a magnitude of 0.5-0.7 MHz above the baseline level. This overshoot might have been caused by an inward shift of the EIA crest position during the post-eclipse period, after an outward shift that happened earlier during the eclipse (Aa et al, 2020). The shift of the EIA crest back to its original position happened simultaneously with the local recovery of foF2 by the restored photoionization, causing foF2 to overshoot the baseline value.…”

“…In this paper, we investigated the ionospheric response to the 26 December 2019 annular solar eclipse event over the Indonesian sector using a combination of ionosonde and GNSS receiver observations, in conjunction with solar image analysis. The present work adds to existing analyses of this particular event performed independently by Aa et al (2020) and Barad et al (2022) over the Indian and Southeast Asian longitudes. Section 2 of this paper describes the methodology, Section 3 describes the observation results, Section 4 presents a discussion of the findings, and Section 5 presents the conclusion.…”

Multi‐Instrument Observations of the Ionospheric Response to the 26 December 2019 Solar Eclipse Over Indian and Southeast Asian Longitudes

“…Aa et al. (2020) and Silwal et al. (2021) have shown a TEC depletion of 20%–50% for the 26 December 2019 solar eclipse.…”

“…Co-ordinated campaigns were conducted using several scientific instruments across the eclipse path in addition to the modeling studies that produced many interesting aspects such as the passage of bow waves, TIDs, and reduction of E and F region density (Zhang et al, 2017). Aa et al (2020) have studied the ionospheric response to the 26 December 2019 solar eclipse using ground-based TEC, EEJ currents, and satellite-based density and temperature measurements. The following results are obtained in their analysis: (a) A reduction in TEC by 30%-50%, (b) significant weakening of EEJ currents over the magnetic equator along the path of annularity, and (c) the altitudinal variation of electron density using SWARM and DMSP satellites showed a considerable reduction in the topside ionosphere but enhancement in temperature at 850 km, (d) increase of 20%-40% in Equatorial Ionisation Anomaly (EIA) after the eclipse in the noon hours are attributed by the eclipse driven neutral winds and electrodynamics.…”