Showing papers on "Solar eclipse published in 2022"

New Observations of the IR Emission Corona from the 2019 July 2 Eclipse Flight of the Airborne Infrared Spectrometer

Abstract: The Airborne Infrared Spectrometer (AIR-Spec) was commissioned during the 2017 total solar eclipse, when it observed five infrared coronal emission lines from a Gulfstream V (GV) research jet owned by the National Science Foundation (NSF) and operated by the National Center for Atmospheric Research (NCAR). The second AIR-Spec research flight took place during the July 2, 2019 total solar eclipse across the South Pacific. The 2019 eclipse flight resulted in seven minutes of observations, during which the instrument measured all four of its target emission lines: S XI 1.393 $\mu$m, Si X 1.431 $\mu$m, S XI 1.921 $\mu$m, and Fe IX 2.853 $\mu$m. The 1.393 $\mu$m line was detected for the first time, and probable first detections were made of Si XI 1.934 $\mu$m and Fe X 1.947 $\mu$m. The 2017 AIR-Spec detection of Fe IX was confirmed and the first observations were made of the Fe IX line intensity as a function of solar radius. Telluric absorption features were used to calibrate the wavelength mapping, instrumental broadening, and throughput of the instrument. AIR-Spec underwent significant upgrades in preparation for the 2019 eclipse observation. The thermal background was reduced by a factor of 30, providing a 5.5x improvement in signal-to-noise ratio, and the post-processed pointing stability was improved by a factor of five to $<$10 arcsec rms. In addition, two imaging artifacts were identified and resolved, improving the spectral resolution and making the 2019 data easier to interpret.

Effects of Total Solar Eclipse on Ionospheric Total Electron Content over Antarctica on 2021 December 4

Abstract: The effects of a total solar eclipse that occurred on 2021 December 4 on ionospheric total electron content (TEC) over Antarctic stations were studied. The study was based on GPS data obtained over Antarctica on the day of the eclipse and the days before and after the eclipse over six GPS stations. The findings of this study show that a total solar eclipse lowers the amount of ionization reaching the Earth’s surface with TEC values dropping across the stations. Finally, the enhancement of ΔTEC is quite different from one station to another station. This may also be due to the effect of solar heating conditions and the density of the Sun as exerted over the stations with the Sun side over one station and the clouded part over the others.

A multi-instrumental and modeling analysis of the ionospheric responses to the solar eclipse on 14 December 2020 over the Brazilian region

Abstract: Abstract. This work presents an analysis of the ionospheric responses to the solar eclipse that occurred on 14 December 2020 over the Brazilian sector. This event partially covers the south of Brazil, providing an excellent opportunity to study the modifications in the peculiarities that occur in this sector, as the equatorial ionization anomaly (EIA). Therefore, we used the Digisonde data available in this period for two sites: Campo Grande (CG; 20.47∘ S, 54.60∘ W; dip ∼23∘ S) and Cachoeira Paulista (CXP; 22.70∘ S, 45.01∘ W; dip ∼35∘ S), assessing the E and F regions and Es layer behaviors. Additionally, a numerical model (MIRE, Portuguese acronym for E Region Ionospheric Model) is used to analyze the E layer dynamics modification around these times. The results show the F1 region disappearance and an apparent electronic density reduction in the E region during the solar eclipse. We also analyzed the total electron content (TEC) maps from the Global Navigation Satellite System (GNSS) that indicate a weakness in the EIA. On the other hand, we observe the rise of the Es layer electron density, which is related to the gravity waves strengthened during solar eclipse events. Finally, our results lead to a better understanding of the restructuring mechanisms in the ionosphere at low latitudes during the solar eclipse events, even though they only partially reached the studied regions.

Responses of the Very Low Frequency Transmitter Signals During the Solar Eclipse on December 26, 2019 Over a North–South Propagation Path

Abstract: During the solar eclipse, the perturbation of ionospheric D layer changes the characteristics of the Earth’s Ionospheric Waveguide (EIWG) on which the very low frequency (VLF, 3–30 kHz) wave propagation depends. Therefore, the amplitude and phase of the VLF signal transmitted through the waveguide will be abnormal. In this article, based on the VLF transmitter signals observed in Suizhou (31.57°N, 113.32°E) during the total solar eclipse on December 26, 2019 and the days before and after, the variation characteristics of VLF transmitter signals along the north–south propagation path are analyzed in detail. Responses of the amplitude and phase of the signal during the solar eclipse are closely related to the solar obscuring rate. There is a positive correlation between the signal fluctuation and the solar obscuring rate, and the peak time of the two has a delay of ~5 min. By adopting the amplitude and phase of the observed signals and performing the Long Wavelength Propagation Capability (LWPC) propagation simulations, the electron density of the ionosphere over the propagation path is calculated. The results show that the electron density profile above the path during the solar eclipse changes significantly. The electron density decreases with a maximum drop of ~53.5% at the 70 km height, and the reflection height of the signal increases correspondingly. The obtained results are useful to better understand the propagation characteristics of VLF transmitter waves and the corresponding response features of the ionospheric D layer to solar radiation flux variations, especially during the solar eclipse.

Enhancement of Electron Density in the Ionospheric <i>F</i> ₂ Layer Near the First Contact of the Total Solar Eclipse on 21 August 2017

Abstract: It can be expected that a moon shadow of solar eclipse can largely reduce the ionospheric electron density (Ne) during the obscuration. However, in this study, the total electron content (TEC) from the ground-based Global Navigation Satellite System receivers recorded a significant Ne enhancement over the continental United States (CONUS) near the first contact of the total solar eclipse on 21 August 2017. The ionosonde observations of the F2-layer peak density (NmF2) and its height (hmF2) over Idaho National Lab (43.81°N, 112.68°W, 99.6% obscuration), ID, and Boulder (40°N, 105.3°W, 93.1% obscuration), CO, verified the unexpected early enhancement. The ionospheric Ne starts to enhance at ∼1520 UT (before the obscuration) and increases by ∼25% to ∼80% at ∼1600 UT (near the first contact) in the F2 layer. The early enhancement reveals the ascension of the F2 layer that tilted east over the CONUS.

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

Abstract: In 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.

Temperature response to the June 2020 solar eclipse observed by FORMOSAT-7/COSMIC2 in the Tibet sector

Abstract: Abstract This study explores the response of atmospheric temperature to the annular solar eclipse at the summer solstice on 21 June 2020. The radio occultation (RO) technique of the FORMOSAT-7/COSMIC2 (F7/C2) mission observes the temperature in the troposphere and stratosphere. The RO observations show that the temperature decreases significantly (near 4 to 8 °C) between 5 and 8 km altitudes over the Tibetan Plateau area within the 80% obscuration during the eclipse. The tropopause temperature increases by ~ 2 to 5 °C over the same area. By contrast, the tropopause temperature decreases by ~ 4° to 5 °C over the Indian Ocean. The F7/C2 RO technique captured not only the sudden tropospheric cooling and stratospheric warming over Tibet during the eclipse but also the possible response over the Indian Ocean away from the greatest eclipse.

COCONUT, a Novel Fast-converging MHD Model for Solar Corona Simulations. II. Assessing the Impact of the Input Magnetic Map on Space-weather Forecasting at Minimum of Activity

Abstract: This paper is dedicated to the new implicit unstructured coronal code COCONUT, which aims at providing fast and accurate inputs for space-weather forecasting as an alternative to empirical models. We use all 20 available magnetic maps of the solar photosphere covering the date of 2019 July 2, which corresponds to a solar eclipse on Earth. We use the same standard preprocessing on all maps, then perform coronal MHD simulations with the same numerical and physical parameters. We conclude by quantifying the performance of each map using three indicators from remote-sensing observations: white-light total solar eclipse images for the streamers’ edges, EUV synoptic maps for coronal holes, and white-light coronagraph images for the heliospheric current sheet. We discuss the performance of space-weather forecasting and show that the choice of the input magnetic map has a strong impact. We find performances between 24% and 85% for the streamers’ edges, 24%–88% for the coronal hole boundaries, and a mean deviation between 4° and 12° for the heliospheric current sheet position. We find that the HMI runs perform better on all indicators, with GONG-ADAPT being the second-best choice. HMI runs perform better for the streamers’ edges, and GONG-ADAPT for polar coronal holes, HMI synchronic for equatorial coronal holes, and the streamer belt. We especially illustrate the importance of the filling of the poles. This demonstrates that the solar poles have to be taken into account even for ecliptic plane previsions.

Accuracy of eclipse records in the Anglo-Saxon Chronicle

Abstract: From a comparison with calculation of the dates and descriptions of the allusions to lunar and solar eclipses recorded in the Anglo-Saxon Chronicle, we confirm the identifications of the eclipses given by Swanton in his 1996 translation and annotation. The details of the analysis on which this is based are given in the supplementary material published as an appendix in the on-line edition of the Journal.

Sky Brightness Evaluation at Concordia Station, Dome C, Antarctica, for Ground-Based Observations of the Solar Corona

Abstract: The evaluation of sky characteristics plays a fundamental role for many astrophysical experiments and ground-based observations. In solar physics, the main requirement for such observations is a very low sky brightness value, less than 10-6 of the solar disk brightness ( B⊙ ). Few places match such a requirement for ground-based, out-of-eclipse coronagraphic measurements. One of these places is, for instance, the Mauna Loa Observatory ( ≈3400m a.s.l.). Another candidate coronagraphic site is the Dome C plateau in Antarctica. In this article, we show the first results of the sky brightness measurements at Dome C with the Extreme Solar Coronagraphy Antarctic Program Experiment (ESCAPE) at the Italian-French Concordia Station, on Dome C, Antarctica ( ≈3300m a.s.l.) during the 34th and 35th summer Campaigns of the Italian Piano Nazionale Ricerche Antartiche (PNRA). The sky brightness measurements were carried out with the internally occulted Antarctic coronagraph AntarctiCor. In optimal atmospheric conditions the sky brightness of Dome C has reached values of the order of 1.0 - 0.7×10-6B⊙ .

In the Shadow of the 1919 Total Solar Eclipse: The Two British Expeditions and the Politics of Invisibility **

Abstract: This paper addresses the legendary total solar eclipse of 29 May 1919. Two British teams confirmed the light bending prediction by Albert Einstein: Charles R. Davidson and Andrew C. C. Crommelin in Sobral, Brazil and Arthur S. Eddington and Edwin T. Cottingham on the African island of Príncipe, then part of the Portuguese empire.

Variations in radiation, total ozone and illumination during the solar eclipse of 20 May 1966 at New Delhi

Abstract: A study has been made of the variations of solar and atmospheric radiation. total ozone content during the solar eclipse on 20 May 1966 with the help of available instruments at Radiation Laboratory. New Delhi. Variations in the values of the natural illumination derived from measurements of solar radiation on this day have also been studied and discussed.

Analyses of historical solar eclipse records in Hokkaido Island in the 18–19th centuries

Abstract: Abstract Solar eclipses have been recorded throughout history and across various ethnic groups. Their records have benefitted scientific discussions on multiple topics. These astronomical spectacles have also been recorded in the Japanese archipelago, but little has been known of the historical observations in the northern end: Hokkaido Island (known as Ezo Island until 1869). Here, we analysed three such early eclipse accounts from Hokkaido Island, both philologically and astronomically. We first analysed Tokunai Mogami's eclipse account written in 1786 January, which has been associated with the earliest eclipse record in Hokkaido Island. Our analysis showed that this eclipse was a deep partial solar eclipse outside the annular totality path of a hybrid eclipse, whereas it had previously been associated with an annular solar eclipse. This eclipse was also witnessed in the Ryukyu Kingdom, probably as a deep partial eclipse. We also located eclipse sketches in Kan’ichiro Mozume's diary and confirmed the local visibility of the annular eclipse in Otaru in 1872 June. We further analysed John Batchelor's eclipse folklore and identified the reported eclipse with a total solar eclipse in 1824 June. This folklore reported “tongues of fire and lightning” from the side of the “black dead sun.” This description is morphologically consistent with that of solar coronal streamers around the solar minima. This eclipse is chronologically located around the minimum of Solar Cycles 6/7 and contrasts the Dalton Minimum with the Maunder Minimum, for which coronal streamers were reportedly missing, according to visual observations.

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

Abstract: Here, 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.

Ionospheric Observation Using Equatorial Atmosphere Radar (EAR) Kototabang for the 26 December 2019 Annular Solar Eclipse Research

Abstract: Solar eclipse passage can cause some change in the ionosphere, which makes it a valuable event to be studied using multi-instruments. On 26 December 2019, an annular solar eclipse passed in the vicinity of Equatorial Atmosphere Radar (EAR) at Kototabang station. We utilize the EAR's capability to detect field-aligned irregularities (FAI) to discover changes in the ionosphere during the eclipse. Other instruments also supported the EAR observation. The results of EAR observations show some appearance of FAI (strong echo power backscatter) at the altitude of ionospheric E layers (90–100 km) during the solar eclipse. Traces of strong sporadic E layers (with spread) were also observed on ionograms from the FMCW ionosonde at the exact location, confirming the EAR observation. The appearance of FAI and these sporadic E layers were likely to be related to the solar eclipse event. The results of several other studies also supported this hypothesis. On the eclipse day, we found that the ordinarily occurring FAI at 150 km altitude disappeared; meanwhile, on 25 and 27 December 2019, the 150 km altitude FAI was observed. We suspect that the absence of FAI at the height of 150 km was related to the solar eclipse phenomena. Another interesting finding is a spread echo backscatter around noon on 25 December 2019, one day before the eclipse.

Mesosphere and Lower Thermosphere changes associated with the July 2, 2019 total Eclipse in South America over the Andes Lidar Observatory, Cerro Pachon, Chile.

Abstract: This article presents the results of a week of observations around the 2 July 2019, total Chilean eclipse. The eclipse occurred between 19:22 and 21:46 UTC, with complete sun disc obscuration at 20:38–20:40 UTC (16:38–16:40 LT) over the Andes Lidar Observatory (ALO) at (30.3°S, 70.7°W). Observations were carried out using ALO instrumentation with the goal to observe possible eclipse-induced effects on the mesosphere and lower thermosphere region (MLT; 75–105 km altitude). To complement our data set, we have also utilized TIMED/SABER temperatures and ionosonde electron density measurements taken at the University of La Serena's Juan Soldado Observatory. Observed events include an unusual fast, bow-shaped gravity wave structure in airglow images, mesosphere temperature mapper brightness as well as in lidar temperature with 150 km horizontal wavelength 24 min observed period, and vertical wavelength of 25 km. Also, a strong zonal wind shear above 100 km in meteor radar scans as well as the occurrence of a sporadic E layer around 100 km from ionosonde measurements. Finally, variations in temperature and density and the presence of a descending sporadic sodium layer near 98 km were seen in lidar data. We discuss the effects of the eclipse in the MLT, which can shed light on a sparse set of measurements during this type of event. Our results point out several effects of eclipse-associated changes in the atmosphere below and above but not directly within the MLT.

Effects from the june 10, 2021 solar eclipse in the high-latitude ionosphere: results of gps observations

Abstract: Subject and Purpose. The unique natural phenomena which solar eclipses are can activate coupling between the subsystems of the Earth–atmosphere–ionosphere–magnetosphere system. Following an eclipse, disturbances may get induced in all the subsystems and their associated geophysical fields. It is important that a subsystem’s response does not depend on the phase of the eclipse alone, but also on the state of space weather and the observation site coordinates. The majority of solar eclipses occur at middle and low latitudes. The maximum phase of the June 10, 2021 annular eclipse was observed at high latitudes, including the North Pole. The highlatitude ionosphere is fundamentally different from the mid- and low-latitude ionosphere as it stays in a metastable state, such that any impact may be capable of activating subsystem coupling. The relevance of this study is conditioned by the diversity of the solar eclipse effects in the high-latitude ionosphere. The purpose of this work is to present observational results concerning variations in the total electron content (TEC) in the high-latitude ionosphere in the course of the June 10, 2021 solar eclipse. Methods and Methodology. An array of eleven terrestrial GPS receive stations and eight GPS satellites were used for the observations. Results. The effects from the solar eclipse were distinctly observable at all eleven reception sites and from all the eight satellites. On the average, i.e. with random fluctuations neglected, changes in illumination at ionospheric heights were followed by decreases in the TEC. All of the observation records demonstrated a decrease in the TEC at the early stage of the eclipse. Some 60 to 100 min later the TEC attained a minimum and then returned to virtually the initial value. The lowest observed magnitude of the TEC was 1.0–5.1 TEC units, while, on the average, it was found to be 2.7 ± 1.6 TEC units, or 35 ± 18%. The greatest decrease in the TEC lagged behind the maximum phase of the solar eclipse (lowest illumination at the heights of the ionosphere) by 5–30 min, or 15.7 ± 6.8 min on the average. A few TEC records obtained at different stations showed quasi-periodic variations with the periods ranging from 5 to 19 min and amplitudes of 1 to 12%. Conclusions. The annular eclipse of June 10, 2021 acted to significantly disturb the high-latitude ionosphere where aperiodic and quasi-periodic disturbances of the TEC took place.