Eclipse Day Research Articles

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.

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

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.

Ionospheric responses on the 21 August 2017 solar eclipse by using three-dimensional GNSS tomography

In this study, we have investigated the ionospheric responses on the August 2017 solar eclipse event by using a three-dimensional tomography algorithm with the ground-based GNSS (Global Navigation Satellite System) total electron content observations around Northern America. This three-dimensional ionospheric electron density structure from the tomography can provide us more information regarding the density variations and propagations of disturbances. Results show that the ionospheric electron density depletion triggered by the solar eclipse started from the higher ionosphere and then extended to lower altitudes. The maximum electron density depletion is around 40% compared with the previous day of solar eclipse. After around 30 min of the totality, the electron density continuously returned to the normal level. We further conduct a procedure of Fourier analyses to derive the vertical phase and group velocities of the electron density propagations. Results show that the opposite directions of the vertical phase and group velocities around 220–240 km altitude imply the energy/oscillation source by the solar eclipse.Graphical

Impact of an annular solar eclipse on trace gases and meteorological parameters over Jaipur, Northwestern India

This study aimed to identify the impact of an annular solar eclipse i.e., 21 June 2020 on the variation of meteorological parameters along with trace gases using statistical analyses. The study site is located at Poornima University, Jaipur (26.7796°N, 75.8771°E), Rajasthan, India. The observational analysis indicates a rapid decrease in solar direct radiation (SDR) which varied between 706 and 79 W/m2 during the eclipse. SDR was reduced to 79 W/m2 at the maximum peak of the solar eclipse at 11:55 a.m. at the study location. The comparative analysis shows the variation of SDR during the solar eclipse day, the previous day, and the day after the event. A strong dip was observed in SDR during the annular eclipse day concerning before (734.31 W/m2) and after (734.375 W/m2) eclipse event. Furthermore, the impact of the solar eclipse on temperature (Ts) and Relative Humidity (RH) was analyzed over Jaipur. The statistical analyses demonstrate an apparent decrease in temperature of about 2°C while RH shows a slight increment (3.45%) during the solar eclipse event. The results show an inverse correlation between the solar eclipse and trace gases variations during the eclipse due to the changes in solar radiation, surface temperature, and variation in winds that might affect the photochemical processes.

Convergence Effects on the Ionosphere During and After the Annular Solar Eclipse on 21 June 2020

AbstractIn this study, we analyze the observations of the ionosondes at Wuhan (30.4°N, 114.4°E, 82.4% obscuration), Xiamen (24.2°N, 118.07°E, 97.8% obscuration), and Nanning (22.7°N, 109.25°E, 81.1% obscuration), as well as the total electron content (TEC) from the global ionosphere maps (GIMs) to examine the ionospheric behaviors in the F‐region on 21 June 2020 solar eclipse day. The observations show that a TEC enhancement occurred after the major depression near the center path of the solar eclipse, and it lasts to midnight on the solar eclipse day. Notes that the occurrence of the TEC enhancement is accompanied by the prominent TEC depletion in the southern side of the center path in the nighttime. The independent in situ electron density (Ne) observation from the Swarm‐B satellite and the calibrated TEC profile from the radio occultation technique onboard the FORMOSAT‐7/Constellation Observing System for Meteorology, Ionosphere, and Climate‐2 satellites also observed the long‐lasting enhancement in the F2 region near midnight. The solar eclipse‐induced convergence effects can result in the long‐lasting ionospheric perturbations, which may further cause the spread‐F in the nighttime.

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

AbstractHere, the impact of the 26 December 2019 solar eclipse on the equatorial and low latitude ionosphere has been investigated using ground and space‐based observations over Indian and Southeast Asian longitudes. The high‐resolution Ionosonde observations at Tirunelveli, GPS Total Electron Content (TEC) observations from a chain of GPS receivers along and across the eclipse path, TIMED‐SABER, and Ionospheric Connection Explorer (ICON) satellites were utilized to investigate the eclipse‐induced variations in electron density and thermospheric cooling. We noticed a tremendous increase and decrease in the base height of the F‐layer, resembling the nighttime Pre‐Reversal Enhancement (PRE). Near the eclipse maximum, a strong blanketing sporadic E layer was observed at Tirunelveli with a top frequency of ∼18 MHz for 1 hr and 26 min. Satellite traces (STs) and “U” shaped ionograms were noticed for the first time over Tirunelveli during eclipse maximum and end phases. The “STs” and “U” shaped traces indicate the presence of short‐period gravity waves or TID type of wave perturbations over the Indian region. A maximum of ∼5–7 TECU (30%–40%) decrease in TEC is observed on the eclipse day for iisc, hyde, and tiru stations. Periodogram analyses of TEC data showed the presence of wavelike structures with periodicities of 18–24 min for different stations. Simultaneous observations from the ICON satellite showed an increase and decrease in hmF2 and NmF2 which matches well with the ionosonde observations from Tirunelveli. The temperature profiles from TIMED‐SABER and ICON satellites showed a reduction and enhancement in the lower and upper E regions respectively.

Investigation of gravity wave characteristics in the equatorial ionosphere during the passage of the 15 January 2010 solar eclipse over Tirunelveli

Solar eclipses are known to produce gravity wave disturbances in the atmosphere–ionosphere system in addition to density reduction due to temporary changes in solar radiation. The magnetic equator is ideally located to investigate these waves and their coupling to the equatorial ionosphere due to its unique geometry. Accordingly, the response of the equatorial ionosphere to a rare Annular Solar Eclipse (ASE) observed on 15 January 2010 is investigated using high-resolution observations from Canadian Advanced Digital Ionosonde (CADI) located at Tirunelveli which is a magnetic equator and on the eclipse totality path in India. In addition, simultaneous observations of GPS TEC from Tirunelveli, electron density profiles from Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC), and Equatorial Electrojet (EEJ) strength were analysed. The real height analysis has been performed on the ionosonde data using POLynomial ANalysis (POLAN). The isoheight/isofrequency analysis has been performed using real height on eclipse and control days. The results indicate a reduction of ∼33% in the lower ionosphere whereas no change has been noticed close to the F layer peak on the eclipse day. The isoheight analysis further indicates the presence of gravity waves with dominant periods in the range of 5–30 min. Further analyses have been performed on the altitude variation of dominant waves and their amplitudes/phases using ionosonde to identify whether they are generated in situ or propagated from below. The altitude variation of group and phase velocities showed opposite propagation indicating that they were propagated from the below. In addition, the simultaneous presence of gravity waves in the fmin, TEC, and EEJ strength on eclipse day supports our finding that these waves were propagated from the lower atmosphere.

Decrement of Secondary Gamma Radiation Flux during Solar Eclipses on January 4, 2011 and December 26, 2019 at Udaipur, India

Abstract: The solar eclipses at Udaipur (270 43’ 12.00”N, 750 28’ 48.01”E), India were experimentally observed on January 4, 2011 and December 26, 2019 using a ground-based NaI (Tl) scintillation detector. For the solar eclipse on January 4, 2011, the data files were stored in a computer for a thirty-minute duration from 14.30 IST to 15.00 IST on pre-eclipse normal days as well as on post-eclipse normal days and also on partial eclipse day (January 4, 2011). For solar eclipse on December 26, 2019, cadences of data were collected for three hours from 8 AM to 11 AM on pre-eclipse normal days as well as on post-eclipse normal days and also on eclipse day (December 26, 2019). The analyzed data revealed significant decrement of secondary gamma radiation flux (SGR) on solar eclipse day (January 4, 2011) of about 10 % and on solar eclipse day (December 26, 2019) of about 17 % in the counts of SGR flux on comparison to average counts of normal days. We interpret such decrement of SGR flux on the basis of obstruction effect produced by the Moon during solar eclipses. Keywords: Solar eclipse, Cosmic radiation, Solar radiation, Secondary gamma radiation, Obstruction effect by the Moon.

Enhancement of Secondary Gamma Radiation Flux Energies in the Energy Region from 1400 Kev to 1500 Kev during Lunar Eclipse on June 16, 2011 at Udaipur, India

Abstract: The lunar eclipse at Udaipur (270 43’ 12.00” N, 750 28’ 48.01” E), India was experimentally observed on June 16, 2011 using ground-based NaI (Tl) scintillation detector. Cadences of data were collected at intervals of half an hour. The analyzed data revealed a significant enhancement in the energy region from 1400 keV to 1500 keV of secondary gamma radiation flux (SGRF) on comparison to pre- and after lunar eclipse days. On June 16, we observed additional peaks in the energy spectrum of SGR flux in the energy region extending from 1461.010 keV to 1472.536 keV during the progress of lunar eclipse. We interpret such enhancement of SGR flux energies on the basis of combined phenomenon of gravitational lensing effect of Sun and Earth as well as the Sun’s magnetic field and the interplanetary magnetic field. Due to such combined effect, primary cosmic and solar radiations bend and may cause strong hitting on the less air surface of the Moon, resulting into emission of secondary particle flux mostly gamma radiation, high energy photo electrons, hard X -radiation, muons, protons and neutrons which may be regarded as back scattering from the Moon surface. Energy of backscattered secondary flux is large enough that it gives such enhancement in the energy region from 1400 keV to 1500 keV during lunar eclipse observation. Also, due to combined gravitational effect, cosmic radiation bent and impinged deep inside the atmosphere of Earth, producing a large shower of secondary radiation particles. These collective effects may give such enhancement of secondary gamma radiation flux energies. Keywords: Lunar eclipse, Solar magnetic field, Interplanetary magnetic field, Gravitational lensing, Bending of primary cosmic and solar radiations.

GPS observations of ionospheric TEC variations over Nepal during 22 July 2009 solar eclipse

As the study of ionospheric behavior during various solar activities is an important task, various studies of ionospheric changes during eclipse events have been widely performed in the different regions of the globe. This paper investigates the ionospheric responses to the solar eclipse on 22 July 2009 over Nepal using the total electron content (TEC) measured by dual-frequency Global Positioning System (GPS) receivers. The time-averaged Vertical TEC (vTEC) of ten GPS stations from Nepal is analyzed and it is found that the value of ionospheric TEC decreases due to the reduction of ionizing radiation. In addition, the deviation in the TEC value on eclipse day from the mean vTEC value of the top five quietest days is found to lie in the range ~1–5 TECu at those regions which were associated with the partial eclipse shadow. On the other hand, the region with the total eclipse (BRN2 and RMTE) faced ~6–7 TECu on average reduction in the TEC value. Considering that the eclipse of 22 July 2009 occurred just at sunrise in the Nepalese zone, a maximum reduction of about 5 TECu is very significant. Higher deviation in TEC is therefore linked with the path of totality and the obscuration rate. This study reveals that the ionospheric TEC over Nepal was altered by wave-like energy and momentum transport, as well as obscuration of the solar disc due to the partial and total solar eclipse. Furthermore, the cross-correlation results presented similar type signatures of the eclipse-induced ionospheric modification over Nepal. This research work serves a crucial future reference for the comparative study of change of ionospheric TEC variability over the Nepal region during Eclipse events

TESS Revisits WASP-12: Updated Orbital Decay Rate and Constraints on Atmospheric Variability

Abstract After observing WASP-12 in the second year of the primary mission, the Transiting Exoplanet Survey Satellite (TESS) revisited the system in late 2021 during its extended mission. In this paper, we incorporate the new TESS photometry into a reanalysis of the transits, secondary eclipses, and phase curve. We also present a new K s -band occultation observation of WASP-12b obtained with the Palomar/Wide-field Infrared Camera instrument. The latest TESS photometry spans three consecutive months, quadrupling the total length of the TESS WASP-12 light curve and extending the overall time baseline by almost two years. Based on the full set of available transit and occultation timings, we find that the orbital period is shrinking at a rate of −29.81 ± 0.94 ms yr−1. The additional data also increase the measurement precision of the transit depth, orbital parameters, and phase-curve amplitudes. We obtain a secondary eclipse depth of 466 ± 35 ppm, a 2σ upper limit on the nightside brightness of 70 ppm, and a marginal 6.°2 ± 2.°8 eastward offset between the dayside hotspot and the substellar point. The voluminous TESS data set allows us to assess the level of atmospheric variability on timescales of days, months, and years. We do not detect any statistically significant modulations in the secondary eclipse depth or day–night brightness contrast. Likewise, our measured K s -band occultation depth of 2810 ± 390 ppm is consistent with most ∼2.2 μm observations in the literature.

Impact of 21 June 2020 Annular Solar Eclipse on Meteorological Parameters, O3 and CO at a High Mountain Site in Taiwan

The annular solar eclipse observed on 21 June 2020 over Taiwan provided a rare opportunity to follow the responses of various meteorological parameters and trace gases to the solar eclipse. For the first time, the impact of the solar eclipse on solar radiation, air temperature (T), relative humidity (RH), atmospheric pressure (P), wind speed (WS), and trace gases (ozone and carbon monoxide) is delineated at the Lulin Atmospheric Background Station (LABS; 23.47°N, 120.87°E; 2,862 m MSL) in Taiwan. Over the Taiwan region, the solar eclipse began at 14:49 local time (LT; UTC+8), reached maximum obscuration at 16:13 LT, and finished at 17:24 LT. Compared to the control period (average of 13–20 June 2020), the weather parameters and trace gases show pronounced changes on the day of the eclipse (21 June 2020). A significant decrease in UV-B and solar irradiance at LABS was observed during the peak phase of the solar eclipse due to the occultation of the Sun by the Moon. On the eclipse day, the T decreased significantly (~4°C) after 17 minutes of maximum solar darkening. Due to the cloudiness and low temperatures on the day of the eclipse, 100% RH was apparent during the period of the eclipse at LABS. We also noticed a steady decline in WS just after the onset of the eclipse at LABS. Interestingly, a marked decline in ozone and carbon monoxide was seen during the eclipse day at LABS. Ozone was reduced by about 10 ppb (40%), with a delay of about 2 hours from the peak phase of the eclipse. Overall, our results show the impact of the solar eclipse on high altitude measurements for the first time, and further this work provides a useful new contribution to the literature examining solar eclipse-induced atmospheric changes.

Effect of total lunar eclipse of 27th July 2018 on the D-region ionosphere by using VLF observations

• Total Lunar Eclipse of 27 July 2018 is investigated for its impact on lower ionosphere. • Change in D-region electron density is inferred from VLF observations and modeling. • Nighttime lower ionospheric density during the Total Lunar Eclipse was found to decrease. In this report, an effort for the first time has been made to investigate the effect of the total Lunar Eclipse that occurred on 27th July 2018 (the longest lunar eclipse in the 21st century) on the D-region ionosphere. Very Low Frequency (VLF) navigational transmitter signals recorded at Prayagraj (formally Allahabad) station in India is the primary dataset used. The signals from two VLF transmitters: NWC (19.8 kHz) from Australia, and JJI (22.2 kHz) from Japan, have been utilized. When compared to unperturbed night, NWC signal amplitude showed an anomalous decrease of ∼0.86 dB, while JJI amplitude showed an anomalous increase ∼0.26 dB during the lunar eclipse. The Wait’s lower ionospheric parameters: reflection height ( H’ ) and sharpness factor ( β ) are estimated by using a rather coarse method of modeling of VLF signals anomalies on eclipse day, which comes out to be H’ = 85.25 km & β = 0.689 km −1 and H’ = 84.59 km & β = 0.683 km −1 respectively for NWC and JJI path. Using wait parameters, the electron density ( N e ) profile is estimated and this showed a decrease in N e during eclipse time with reference to the nighttime ambient values. The N e values for the NWC path, showed relatively higher decrease compared to the JJI path. The plausible reasons for observed N e decrease on lunar eclipse night could be due to the reflected lunar Lyman‐α and X-ray’s radiation which may contribute to the nighttime ionization is blocked during the lunar eclipse, thereby decreasing the nighttime lower ionospheric N e .

Atmospheric response to the annular solar eclipse of 26 December 2019 over Cochin, India

• Atmospheric response to annular solar eclipse of December 2019. • Drastic reduction in incoming solar radiation and variations in meteorological variables. • Mean PBL and Tropopause Heights were reduced by 50% and 5.5%. • Detected the presence of internal gravity waves with periodicities of 40–60 min. • Study useful for radiative transfer calculation and also for testing numerical models. The rapid response of the atmosphere to the reduction in solar radiation during the annular solar eclipse on 26th December 2019 with maximum obscurity of 91.16% over Cochin, located in the southwest peninsular India, has been investigated. A suite of instruments encompassing an advanced VHF wind profiling Radar operating at 205 MHz, GPS radiosonde, and automatic weather station was employed to record the temporal and vertical variations in various meteorological parameters. Compared to the corresponding values averaged for two control days neighboring the eclipse day, the temperature, relative humidity, net radiation, pressure and wind speed at the surface were altered by −4.0 °C, +39.6%, −383.0 Wm −2 , +0.62 mb, and −2.6 ms −1 , respectively. The corresponding percentage variations are −13.6%, +71.0%, −67.0%, +0.06%, and −99.0% during the maximum phase of the eclipse, and approached close to the control-day values within about 2 h. Multiple temperature inversions as large as 1 °C were observed up to a height of about 7.3 km. The heights of mean planetary boundary layer (PBL) and tropopause were decreased by about 355 m (−50%) and 900 m (−5.5%), respectively during the peak of obscuration. Meanwhile, the vertical profiles of both the horizontal and vertical wind velocities demonstrate substantial reduction. The vertical wind dispersion, which characterizes the fluctuations in vertical air motion, was reduced by 34% in the PBL compared to its corresponding values on the control days. Subsequently, wavelet spectral analysis of the vertical wind yields a quasi-periodic oscillation indicating the presence of internal gravity waves with periodicities of 40–60 min in the lower altitudes up to 3 km during the eclipse day. Besides reporting the characteristic variations in various atmospheric parameters, the present study reveals the height-time variations in the vertical winds, a vital parameter of significance in the studies of convection, turbulence, and atmospheric waves.

Observations and analysis of the impact of annular eclipse on 10 MHz short-wave signal in Sanya area on June 21, 2020

This paper takes the annular solar eclipse that occurred in China on June 21, 2020, as the background and conducts tests and analysis of shortwave timing sky wave signals. The test group continuously tested the signal field strength data from June 20, 2020, to June 23, 2020. The results show that the shortwave signal field strength on June 21, the day of the annular eclipse, is significantly weaker than that on two other days—before and during the annular eclipse—and there are three obvious jumps in the field strength value. (1) The first jump occurs more than one hour before the annular eclipse, and then, the field strength has an oscillatory attenuation. Between the first jump and the second jump, the overall change trend of the field strength value is an oscillatory decline one. (2) About 25 min before the beginning of the eclipse, the second jump of the field strength occurs; from the second jump to the third jump, that is, before the occurrence of the beginning of the eclipse and the transition phase from the beginning to the middle of the eclipse, the value of the field strength has an oscillatory increase. (3) During the period of 8:00–8:10, the field strength shows a third jump. Although the field strength oscillates after the third jump, it has no obvious increasing or decreasing trend. Based on the results of previous studies on the annular eclipse on that day and the analysis of the theoretical model of radio wave propagation, this paper preliminarily considers that the change in signal field strength is supposed to be caused by the impact of the outbreak of the annular eclipse on the ionosphere. When the annular eclipse occurred, the sunlight reaching the ground is blocked by the Moon, and the ionization degree of electrons in the ionosphere is reduced, resulting in an increase in the penetration factor, and the overall performance of the shortwave signal reaching the ground is weakened.

Differential Impact of an Eclipse on Photosynthetic Performance of Trees with Different Degrees of Shade Tolerance

Solar eclipses represent a natural and unexpected event for plants that can potentially affect photosynthetic performance at the individual level. This effect, however, has seldom been evaluated. Here, we measured the impact of a total solar eclipse on the photosynthetic rate of different tree species—located in the Bosque Fray Jorge National Park, Chile—with varying degrees of shade tolerance. Specifically, we assessed whether the rapid and progressive light limitation facilitated by a solar eclipse would negatively impact the photosynthetic responses of these tree species and whether their photosynthetic performance would have a greater decrease when the percentage of eclipse shadow was higher, particularly in the less shade-tolerant species. To accomplish this, we compared daily changes in the photosynthetic rates of three tree species during a control (non-eclipse) vs. an eclipse day that occurred on 2 July 2019. Overall, tree species showed differences between a non-eclipse and eclipse day in the daily dynamics of their photosynthetic performance, with this trend being most evident at the peak of the solar eclipse. Additionally, each species showed a different pattern of de-epoxidation in accordance with its degree of shade tolerance. Our results suggest that solar eclipses negatively affect the photosynthesis of the studied Chilean tree species, which may be related to energy dissipation capacity via the de-epoxidation of xanthophyll pigments. This effect was more evident in shade-intolerant species, indicating that eclipses can present different consequences for the overall performance of various plant species.

Nighttime Ionosphere Perturbed by the Annular Solar Eclipse on June 21, 2020

AbstractThis study analyzed the total electron content (TEC) observed by 337 ground‐based Global Navigation Satellite System (GNSS) receivers over China and South Asia, the critical frequency of the ionospheric F2 layer (foF2) and its height (hmF2) recorded by the ionosonde at Puer (22.7°N, 101.05°E, 72% obscuration), Yunnan province, during and after the annular solar eclipse on June 21, 2020. The observations show that the eclipse induced not only a daytime major depression but also nighttime perturbations in the ionosphere. The TEC perturbed intermittently from noon to midnight between 85° and 125°E on the eclipse day. The positive and negative changes of the prereversal enhancement respectively occur in the nearby longitudinal sectors of 100°and 115°E. The TEC perturbations behave as a terminator wave that propagates in a northwestward direction after sunset.

Investigation of ionospheric losses for the ‘O+ + O2 → O2 + + O’ reaction during the solar eclipse

In this study, the response of the loss terms for the ‘O+ + O2 → O2 + + O’ reactive reaction, which is an important charge transfer process in the upper ionosphere, to the partial solar eclipse on March 29, 2006 over Kharkov city located in the European mid-latitude was analyzed together with the reference days of 28 and 30 March. The measurement data were obtained from the Kharkov incoherent scatter radar. The loss terms for O+ + O2 reaction increased at the time of maximum covering and changed inversely proportional to the ionospheric height. The maximum loss terms were obtained at heights of 252, 303 and 353 km on the eclipse day, while it was seen at the 399 km on March 30. For the four altitudes, the maximum and minimum (except 353 and 399 km) values on the eclipse day were seen at different time intervals. The important finding of this analysis is that the solar eclipse effect on the loss terms gives different results at the upper and lower heights and the complexity of the ionospheric behaviour with the increase in altitude. Another important result of this analysis reveals that the effect of solar eclipse on ionospheric loss terms is greater on the day after the eclipse compared to the day before the eclipse. The results of this study show that eclipse-induced mechanisms such as electric field, neutral wind changes, lunar tides, atmospheric gravity waves (AGWs) and diffusion can continue to impact the ionosphere during and after the solar eclipse.