Annular Solar Eclipse Research Articles

Multi‐Frequency SuperDARN HF Radar Observations of the Ionospheric Response to the October 2023 Annular Solar Eclipse

AbstractAn annular solar eclipse was visible on 14 October 2023 from 15:00–21:00 UT as its path traveled across North, Central, and South America. In this letter, we present the first multi‐frequency Super Dual Auroral Radar Network (SuperDARN) observations of the bottomside ionospheric response to a solar eclipse using a novel experimental mode designed for the October 2023 annular eclipse. We compare our results from the mid‐latitude Christmas Valley East radar with measurements of the vertical electron density profile from the nearby Boulder Digisonde, finding the changes in 1‐ and 2‐hop ground scatter skip distance are well correlated with the ‐layer density response, which lags the peak obscuration by 30 min. Changes in the line‐of‐sight Doppler shifts are better aligned with the time derivative of eclipse obscuration.

Annular solar eclipse effects observed over Mexico on October 14, 2023: a multi-instrument study

Annular solar eclipse effects observed over Mexico on October 14, 2023: a multi-instrument study

Main features of the geomagnetic effect of the October 14, 2023 annular solar eclipse in the Americas

The purpose of this paper is to investigate temporal variations in the northward, X, eastward, Y, and downward, Z, components of the geomagnetic field recorded during the October 14, 2023 annular solar eclipse, which main features include its annularity, the eclipse occurrence from local dawn to local dusk, its magnitude variation from 0.30 to 0.86, and the longest ever-observed path across the mainland of the Americas, covering latitudes from ∼65°N to 12°S. The analysis was made possible due to the data on temporal variations in the northward, X, eastward, Y, and downward, Z, components of the geomagnetic field collected at thirteen International Real-time Magnetic Observatory Network magnetometer stations (https://imag-data.bgs.ac.uk/GIN_V1/GINForms2). The solar eclipse acted to cause non-sinusoidal and quasi-sinusoidal perturbations having temporal durations of 180–240 min in all geomagnetic field components on a global scale (∼8000 km). The X-component experienced the largest perturbations attaining 10–20 nT, and the Z-component underwent the smallest disturbances. The quasi-sinusoidal perturbation amplitude did not exceed 5–6 nT, and the period most often showed variations within 15–40 min. The magnetic effect exhibited a tendency to increase with solar eclipse magnitude, while the magnitude of the effect has been shown to be significantly dependent on geographic coordinates, local time, ionospheric state, and the patterns of ionospheric currents as well. During the solar eclipse, the electron density depletion was estimated to be ∼0.10 to ∼0.40–0.60 when the eclipse obscuration Amax varied from 19% to 82%. The movement of the lunar shadow was accompanied by the generation of atmospheric gravity waves with period of ∼10–80 min and by electron density perturbations with amplitudes of the order of 0.01–0.03. The estimates made on the assumption that the magnetic effect is due to the ionospheric current disruptions show good agreement with the observations.

Effects of an annular solar eclipse on montane streamwater quality in New Mexico, USA

Effects of an annular solar eclipse on montane streamwater quality in New Mexico, USA

Impact of the annular solar eclipse on December 26, 2019 on the foraging visits of bees

Solar eclipse has remarkable effect on behavior of animals. South India experienced a 97% magnitude annular eclipse on December 26, 2019 during 08:04–11:04 h with the totality phase appeared during 09:25–09:30 h. We investigated whether the foraging activity of the bees was limited by the eclipse, what bees are affected most, and which part of the eclipse was critical for bee activities to understand how a group of insects that rely the Sun, the sunlight, and the sun rays for their navigation and vision behaves to the eclipse. We opted to watch the bees in their foraging ground, and selected the natural flower populations of Cleome rutidosperma, Hygrophila schulli, Mimosa pudica, and Urena sinuata—some of the bee-friendly plants—to record the visitor richness and visitation rate on the flowers on eclipse and non-eclipse days and during the hour of totality phase and partial phase of the eclipse. Fewer flower-visiting species were recorded on the eclipse day than on the non-eclipse days, but in the period of totality, very few bee species were active, and limited their activity to only one population of C. rutidosperma. Visits of honey bees and stingless bees were affected most, but not that badly of solitary bees and carpenter bees. Bees, particularly the social bees use Sun for navigation and deciphering information on forage sources to fellow workers. The eclipse, like for many other animals, might hamper bees’ orientation, vision, and flight.

Solar bird banding: Notes on changes in avian behavior while mist-netting during an eclipse

Solar eclipses present rare celestial events that can elicit unique behavioral responses in animals, yet comprehensive studies on these phenomena, particularly concerning bird behavior, remain limited. This study, conducted at the Red Butte Canyon Research Natural Area in Utah during the annular solar eclipse on October 14, 2023, aimed to document and analyze avian activity using bird banding data. Leveraging 11 years of banding records, we observed a surprising positive peak in bird captures, indicating increased activity during the eclipse, challenging conventional expectations of decreased activity during peak totality. The unexpected, record-breaking captures on the eclipse day at this location, which also surpassed the average trend in captures over time for 18 other banding days in mid-October, highlights the complexity of bird behavior during celestial events. This study marks the first known published effort to conduct bird banding during a solar eclipse. Quantitative analyses, including species composition and capture trends, contribute to a nuanced understanding of avian responses to the eclipse. This study underscores the importance of empirical research in unraveling the intricacies of how birds navigate and adapt to unique environmental conditions created by solar eclipses.

Study of the response of the upper atmosphere during the annular solar eclipse on October 14, 2023

A solar eclipse is a fascinating event that gives a unique opportunity to study the ionospheric characteristics in a controlled blockage of solar radiation. We present the upper atmosphere’s response, mostly F-layer, during the annular eclipse on October 14, 2023. This eclipse was mostly visible from the North and South American regions with a maximum obscuration of around 91%. We study the response of the ionospheric Total Electron Content (TEC) and the critical frequency of the F2 layer (f0F2) for three consecutive days (October 13 to 15, 2023) using ground and space-based techniques. We present the ionospheric response for a large area that covers the path of the solar eclipse of latitude and longitude range from 50°N to 10°S and 30°W to 150°W. For the ground-based observation, we use fifty-five International GNSS Service (IGS) stations and eleven Global Ionospheric Radio Observatory (GIRO) Digisonde stations that cover the annular and partial solar eclipse and are in the close vicinity of the annularity belt. We compute the vertical TEC (VTEC) and f0F2 from this database and check their temporal and spatial variations. It is found that the VTEC, as computed from the IGS stations, mostly shows decrements during the partial blockage of the sun by the lunar disc. The VTEC, as computed from the GIRO database, also shows a decreasing trend but with comparatively more oscillating in nature. The f0F2 shows a similar decreasing trend due to the solar eclipse. For space-based observation, we use the Swarm satellite data for the tracks that have gone through the annularity belt. Also, a spatiotemporal study is executed using the Global Ionospheric Map (GIM) database. For both cases, the VTEC shows a prominent depletion. We investigate the variation in the percentage change in VTEC as a function of obscuration and observe a positive correlation between them. We also compute the time difference between the maximum eclipse and the maximum TEC modulation to investigate the response time profiles of the ionosphere at different receiving stations. All the methods give satisfactory and consistent outcomes that corroborate the physical mechanism of ionospheric variabilities due to the effect of the solar eclipse. We check the geomagnetic condition to eliminate the scope of contamination and observe that their values are normal during the study.

The dynamic effects of solar eclipses of October 25, 2022, and October 14, 2023, on GPS-derived total electron content

This study analyzes total electron content (TEC) variations during two solar eclipse events that occurred on October 25, 2022, and October 14, 2023. The solar eclipse of October 25, 2022, was a partial solar eclipse, while the eclipse of October 14, 2023, was an annular solar eclipse. For this study, the data of eight International GNSS Service (IGS) stations from different eclipse coverage zones are used to analyze TEC variations. It is found that the stations located in the maximum eclipse cover zone exhibited notable decreases in TEC values. The minimum variation of about 11.76% in TEC values is observed at the station situating in about 20 percent eclipse cover zone, while it varies from 22% to 38% at the stations falling in about 60 percent eclipse cover zone. The highest variation in TEC values of about 44% is found at the stations in about 80 percent eclipse cover zone. The time of occurrence of maximum depletion in TEC values at each station is in line with their longitudinal sequence. Atmospheric gravity waves (AGWs) are also observed by performing wavelet analysis on TEC data. The global TEC maps visualize and confirm observed TEC variations, providing spatial and temporal insights into the ionospheric response. This analysis highlights the influence of station location and eclipse coverage on the magnitude and spatial distribution of TEC variations.

Monitoring the ionospheric conditions during the annular solar eclipse December 2019: A case study

This study investigates the ionospheric response to the December 26, 2019 annular solar eclipse over the southern tip of the Asia region, focusing on Malaysia, Sumatra, and Singapore. Utilizing data from GPS stations and ionosondes along the eclipse path, variations in Total Electron Content (TEC) and ionospheric foF2 parameters were analysed to assess the eclipse's impact. Results indicate a slight northward depletion of TEC, possibly linked to the Equatorial Ionization Anomaly (EIA), with up to −30% of depletions observed across all sites. Time delays in TEC and foF2 parameter responses suggest the influence of recombination and photochemical processes. Differences in depletion percentages between TEC and foF2 parameters may stem from production rate reductions during the eclipse. Post-sunset enhancements in TEC and foF2 parameters suggest the formation of ionospheric plasma blobs associated with Travelling Ionospheric Disturbances (TIDs) during the eclipse. While consistent with trends observed in prior studies, the study's findings highlight regional variations in ionospheric effects. This study enhances our understanding of ionospheric dynamics during solar eclipses and paves the way for further exploration in this area.

Observations of the Polarized Solar Corona During the Annular Eclipse of 14 October 2023

We present results of a dual eclipse expedition to observe the solar corona from two sites during the annular solar eclipse of 14 October 2023 using a novel coronagraph designed to be accessible for amateurs and students to build and deploy. The coronagraph (CATEcor) builds on the standardized eclipse observing equipment developed for the Citizen CATE 2024 experiment. The observing sites were selected for likelihood of clear observations, for historic relevance (near the Climax site in the Colorado Rocky Mountains), and for centrality to the annular eclipse path (atop Sandia Peak above Albuquerque, New Mexico). The novel portion of CATEcor is an external occulter assembly that slips over the front of a conventional dioptric telescope, forming a shaded-truss externally occulted coronagraph. CATEcor is specifically designed to be easily constructed in a garage or “makerspace” environment. We successfully observed some bright features in the solar corona to an altitude of approximately 2.25 R⊙ during the annular phases of the eclipse. Future improvements to the design, in progress now, will reduce both stray light and image artifacts; our objective is to develop a design that can be operated successfully by amateur astronomers at sufficient altitude even without the darkened skies of a partial or annular eclipse.

D-region ionospheric disturbances due to the December 2019 solar eclipse observed using multi-station VLF radio network

We present the low-latitude D-region (60–90 km) ionospheric disturbances due to the December 2019 annular solar eclipse observed using the multi-station Very Low Frequency (VLF) radio network in West Bengal, India. VLF signals from communication transmitters were received from ten places using low-cost VLF radio receivers. The receivers were capable of recording the amplitudes of VLF signals mainly from the transmitters VTX, India at 18.2 kHz and NWC, Australia at 19.8 kHz. During the solar eclipse, the VTX signal experienced considerable positive, negative, and mixed-type amplitude variations depending on the propagation lengths between the transmitter and receivers, whereas the NWC signal displayed a relatively small amplitude response. We have also found that the highest VLF signal disturbances in each propagation path occurred after the time when the solar obscuration was maximum over the entire path. We used the observations of the VTX signal to formulate the relationship between solar obscuration and D-region electron density reduction during the solar eclipse. On the basis of this, we presented the electron density distribution of the D-region ionosphere during the solar eclipse across the Indian subcontinent. This study shows a useful method for integrating VLF observations and simulations to estimate the D-region electron density distribution over a vast area during a solar eclipse.

Variation in Total Electron Content Over Ethiopia During the Solar Eclipse Events

AbstractThis work studies variations of ionospheric total electron content (TEC) during four distinct solar eclipse events over the Ethiopia region. Dual‐frequency global positioning system (GPS) data obtained from UNAVCO over Addis Ababa (9.036°N, 38.76°E) and Bahir Dar (11.6°N, 37.34°E) stations are used to examine the ionospheric variability during two annular solar eclipses on 15 January 2010 and 1 September 2016, a partial solar eclipse on 4 January 2011, and a hybrid solar eclipse (the eclipse path starts out as annular but later changes to total) on 3 November 2013. The results show a significant decrease in TEC values during the occurrence of the solar eclipses. Specifically, the TEC values are reduced to −20% and −10% during the annular eclipse on 15 January 2010, −33% and −38% during the partial solar eclipse on 4 January 2011, −26% and −24% during the annular solar eclipse on 1 September 2016, over the Addis Ababa and Bahir Dar stations, respectively. There is only minimal change in TEC of −8% and −9% at Addis Ababa and Bahir stations, respectively, during the 3 November 2013 solar eclipse even if the obstruction rate is high over the study area. Furthermore, the study shows that the spatial gradient of TEC reduction varies at different locations, which is attributed to the distinct amount of reduction in solar radiation reaching the Earth's surface, resulting in reduced photo‐ionization. Overall, this study provides insightful information about the behavior of the ionospheric TEC during solar eclipses over Ethiopia and emphasizes the use of dual‐frequency GPS data in tracking the variations of the TEC.

Annular Solar Eclipse Day at the Solar Eclipse Village in Uvalde County, Texas: Personal Insights

Annular Solar Eclipse Day at the Solar Eclipse Village in Uvalde County, Texas: Personal Insights

The October 2023 Annular Solar Eclipse at Angelo State University: Creating a Memorable Viewing Event for the Entire Community

The October 2023 Annular Solar Eclipse at Angelo State University: Creating a Memorable Viewing Event for the Entire Community

2‐D Total Electron Content and 3‐D Ionospheric Electron Density Variations During the 14 October 2023 Annular Solar Eclipse

AbstractThis study investigates the ionospheric total electron content (TEC) responses in the 2‐D spatial domain and electron density variations in the 3‐D spatial domain during the annular solar eclipse on 14 October 2023, using ground‐based Global Navigation Satellite System (GNSS) observations, a novel TEC‐based ionospheric data assimilation system (TIDAS), ionosonde measurements, and satellite in situ data. The main results are summarized as follows: (a) The 2‐D TEC responses exhibited distinct latitudinal differences. The mid‐latitude ionosphere exhibited a more substantial TEC decrease of 25%–40% along with an extended recovery time of 3–4 hr. In contrast, the equatorial and low‐latitude ionosphere experienced a smaller TEC reduction of 10%–25% and a faster recovery time of 20–50 min. The minimal eclipse effect was observed near the northern equatorial ionization anomaly crest region. (b) The ionospheric electron density variations during the eclipse were effectively reconstructed by TIDAS data assimilation in the 3‐D domain, providing important altitude information with validity. (c) The ionospheric electron density variations showed a notable altitude‐dependent feature. The eclipse led to a substantial electron density reduction of 30%–50%, with the maximum depletion occurring around the ionospheric F2‐layer peak height (hmF2) of 250–350 km. The post‐eclipse recovery of electron density exhibited a relatively slower pace near the F2‐layer peak height than that at lower and higher altitudes.

Astrophotography of the October 14th, 2023, Annular Solar Eclipse

Astrophotography of the October 14th, 2023, Annular Solar Eclipse

The 2023 Annular Solar Eclipse in South Texas: Community Engagement and Personal Insights

The 2023 Annular Solar Eclipse in South Texas: Community Engagement and Personal Insights

Examining the effects of a pre-noon annular Solar Eclipse on equatorial electrodynamics: Evidence for a subsequent post-noon enhancement in plasma density

On 26 December 2019, an annular solar eclipse occurred in the southern part of the Indian subcontinent, which falls within the Equatorial ElectroJet (EEJ) region. This presented an opportunity to study the effects of a high-obscuration annular solar eclipse (93.3%) and of the special tides that accompany an eclipse. Eclipses are known to affect the electrodynamics of the equatorial region and the distribution of plasma in the low-latitude ionosphere. On December 26, 2019, different phenomena were indeed seen over different time scales. Around the time of the eclipse, there was a depletion in the total electron content (TEC) of the ionosphere, as inferred from GNSS receiver systems placed along the eclipse path in and around the EEJ region. Magnetometer measurements indicated a weakening of the EEJ current in this area not just when the eclipse took place but for the rest of the day as well. Observations from a digital-ionosonde located in Trivandrum (8.52°N, 76.94°E; 0.33°N dip-latitude) revealed that the ionospheric F-layer moved downwards just after obscurity maximum. Shortly after the F region was observed to move back upward, a one-hour long strong blanketing sporadic E-layer was triggered even though there was only a weakening of the EEJ but no reversal in the associated magnetic perturbations. Simulations from our quasi-two dimensional model clearly show that though there was no Counter Electrojet, there was indeed a weakening of the zonal field on 26 December 2019 during the eclipse and the post-eclipse period. The overall weakening trend lasted until late afternoon. Other notable features were uncovered on a time scale of several hours after the passage of the eclipse. While the day-long weakening of the EEJ is consistent with special tides related to the lunar trajectory, we also observed unusually large amplitude undulations in both vertical-TEC and F2-region peak plasma density over a five-hour time scale, starting around 2:00 PM LT. These undulations were consistent with the zonal electric field variations reconstructed from the magnetometer data.

The Responses of Ozone to the Solar Eclipse on the 21st of June 2020 in the Mesosphere and Upper Stratosphere

Microwave Limb Sounder (MLS) observations showed an obvious variation of ozone concentration during the annular solar eclipse on 21 June 2020 in the mesosphere and upper stratosphere. Ozone concentration slightly reduced near 40 km in the regions of 24°N–36°N, and increased in low latitudes at 40 km. In the heights of 45–60 km, the increase in ozone concentration in most of the regions was obvious. The ozone increases and decreases were more obvious between 60–65 km, where enhancement took the leading role. The nighttime ozone variation was weaker than the daytime in most of the heights of 30–65 km. The variation of HO2 and CO is investigated to study the photochemical and dynamical causes of ozone variation. As HO2 decreased at 1 hPa and increased at 60–65 km, ozone variation shows a mostly reversed relationship to HO2 variation. CO increased at 32–39 km and decreased at 52–60 km, which was related to the upwelling at these heights. The dynamic processes also contributed to the decrease in ozone concentration at 40 km and increase at 50–60 km.

Three‐Dimensional Ionospheric Evolution and Asymmetry of the Electron Density Depletion Generated by the 21 June 2020 Annular Solar Eclipse

AbstractThe three‐dimensional computerized ionospheric tomography (3DCIT) technique has been used to reconstruct the ionospheric response to the 21 June 2020 annular solar eclipse and the results are evaluated by constellation observing system for meteorology, ionosphere, and climate observations. The 3DCIT‐derived electron density (Ne) difference between the eclipse and quiet days showed that the Ne depletion was between 200 and 550 km and the maximum magnitude was about −3.0 × 1011 el/m3 which was at 280 km in altitude. The contributions from below 250 and 350 km altitudes to Vertical Total Electron Content (VTEC) depletion were ∼30% and ∼60%, respectively. Significant asymmetry of Ne depletion with respect to the eclipse path was captured in 3DCIT results, and the deviation conditions between the Ne depletion central line and eclipse path varied at different altitudes. Simulations with the thermosphere‐ionosphere‐electrodynamics general circulation model generally showed consistent ionospheric variations with GNSS (Global Navigation Satellite System) VTEC and 3DCIT electron density. Furthermore, term analysis on the ion continuity equation indicates that the asymmetry of Ne depletion was mainly induced by the neutral wind disturbance which converged toward the eclipse region and caused opposite transport effects on both sides of the eclipse path. The thermospheric composition was also changed by disturbed neutral wind and impacted plasma production and loss rates, contributing to the Ne depletion asymmetry.