Showing papers on "Solar eclipse published in 2021"

Graphical evidence for the solar coronal structure during the Maunder minimum: comparative study of the total eclipse drawings in 1706 and 1715

Abstract: We discuss the significant implications of three eye-witness drawings of the total solar eclipse on 1706 May 12 in comparison with two on 1715 May 3, for our understanding of space climate change. These events took place just after what has been termed the “deep Maunder Minimum” but fall within the “extended Maunder Minimum” being in an interval when the sunspot numbers start to recover. Maria Clara Eimmert’s image in 1706 is particularly important because she was both a highly accomplished astronomical observer and an excellent artist: it was thought lost and was only re-discovered in 2012. Being the earliest coronal drawings of observational value yet identified, these drawings corroborate verbal accounts a corona without significant streamers, seen at totality of this and another eclipse event in 1652 during the Maunder Minimum. The graphical evidence implies that the coronal solar magnetic field was not lost but significantly weakened and the lack of coronal structure means there was little discernable open flux (either polar or at lower latitudes) even during the recovery phase of the Maunder Minimum. These observations provide evidence for a different state of oscillation of the solar dynamo, and hence behaviour of the Sun, in comparison with that during normal solar cycle minima (when a streamer belt between two polar coronal holes is visible) or near normal sunspot maxima (when coronal structure is caused by coronal holes at all latitudes) even to observers without a telescope.

The Color and Brightness of the F-corona Inferred from the 2019 July 2 Total Solar Eclipse

Abstract: Total solar eclipses (TSEs) provide a unique opportunity to quantify the properties of the K-corona (electrons), F-corona (dust) and E-corona (ions) continuously from the solar surface out to a few solar radii. We apply a novel inversion method to separate emission from the K- and F-corona continua using unpolarized total brightness (tB) observations from five 0.5 nm bandpasses acquired during the 2019 July 2 TSE between 529.5 nm and 788.4 nm. The wavelength dependence relative to the photosphere (i.e., color) of the F-corona itself is used to infer the tB of the K- and F-corona for each line-of-sight. We compare our K-corona emission results with the Mauna Loa Solar Observatory (MLSO) K-Cor polarized brightness (pB) observations from the day of the eclipse, and the forward modeled K-corona intensity from the Predictive Science Inc. (PSI) Magnetohydrodynamic (MHD) model prediction. Our results are generally consistent with previous work and match both the MLSO data and PSI-MHD predictions quite well, supporting the validity of our approach and of the PSI-MHD model. However, we find that the tB of the F-corona is higher than expected in the low corona, perhaps indicating that the F-corona is slightly polarized -- challenging the common assumption that the F-corona is entirely unpolarized.

Global Positioning System Observations of Ionospheric Total Electron Content Variations During the 15th January 2010 and 21st June 2020 Solar Eclipse

Abstract: The dual-frequency global positioning system (GPS) data acquired from the UNAVCO over different places of Nepal were processed to examine the eclipse-triggered consequences on total electron content (TEC) in response to the annular solar eclipse of 15th January 2010 and 21st June 2020. These occasions were exceptional since they occurred during solar minimum, additionally as in a magnetically quiet period. The eclipse phase coincided with the peak ionization-time at the equatorial and low latitude regions. The solar eclipse of 21 st June 2020 was an annular solar eclipse with a magnitude of 0.994. Nepal has witnessed a partial eclipse, starting at ∼10:53 NST (05:08 UT), reached the maximum at ∼12:40 NST (6:55 UT), and ended at ∼ 14:24 NST (8:39 UT) with the total duration of 3 h and 31 min. The annular solar eclipse of 15th January 2010 had the magnitude of 0.919 and Nepal has witnessed a partial eclipse starting at ∼12:24 NST (6:39 UT), reached the maximum at ∼ 14:10 NST (8:25 UT), and ended at ∼15:40 NST (9:55 UT). The eclipse effect occurs as a trough-like depression in the curve of TEC at all the GPS stations indicates the effect of sudden attenuation of solar extreme ultra-violet irradiation on decayed electron content in the ionosphere over the region. Moreover, the extent of the exhaustion in ionospheric TEC was studied by comparing the eclipse day TEC with mean diurnal ionospheric TEC of five quietest days of the month to investigate the eclipse effect on the electron density of the ionosphere over the stations. The study additionally reveals that the measure of the decrease in vertical value of total electron content is proportional to the obscuration of the lunar disc, that is closely associated with the electron production via the photoionization process. Observing the values of TEC during the eclipse day and comparing it with other quiet days, our study showed an apparent variation during the time of the eclipse, which agrees with previous studies on ionospheric responses to the eclipse as well as theoretical assumptions.

Conjugate ionospheric perturbation during the 2017 solar eclipse

Abstract: We report new findings of total electron content (TEC) perturbations in the southern hemisphere at conjugate locations to the northern eclipse on 21 August 2017. We identified a persistent conjugat...

Engaging the Public With the Great American Eclipse of 2017

Abstract: The August 21st 2017 Total Solar Eclipse public engagement program was arguably the largest, most complex, and most inclusive engagement program ever achieved by NASA. This was the first total solar eclipse to cross the continental United States since 1979 and the first one to cross from coast to coast since 1918. NASA worked with a broad set of organizations as well as states and cities to help support and promote events across the country before and during the event. It was much more than an event, though: it was an opportunity to engage over two billion people in the United States and throughout the world with rich STEM educational content, vivid imagery, safety messages, and citizen science opportunities. This amazing spectacle of nature is not the only such opportunity for the hemisphere. A total solar eclipse crossed Chile and Argentina in July 2019 and did so again in December 2020. The United States will have another chance to experience this in April 2024. With all the eclipse excitement in North and South America over a relatively short period of time, the public continues to hunger for more. NASA hopes to again help excite and inform the world of the next opportunity for the Sun’s corona to shine.

Ionospheric Response over Nepal during the 26 December 2019 Solar Eclipse

Abstract: On 26 th December 2019, during morning hours, an annular solar eclipse having a magnitude of 0.96 with a 118 km wide antumbra occurred and lasted for 3 minutes and 40 seconds at the point of maximum eclipse. The partial eclipse was visible in most of Asia, parts of North/East Africa, and North/West Australia. In the context of Nepal, only the partial eclipse was visible from ~ 8:34 LT (02:51 UT) and ended at ~ 11:40 LT (05:55 UT). It was 2 hours 47 mins and 54 secs long with the maximum visible eclipse time at ~ 10:01 LT (04:16 UT). Our study is based on Global Navigation Satellite System (GNSS) measurements from a widely distributed Global Positioning System (GPS) network over different places of Nepal on the day of the eclipse, a day before, and a day after the eclipse. We investigated the ionospheric behavior through the changes in Total Electron Content (TEC) during the partial eclipse by using the data archived at the five different GPS stations of Nepal. The result reveals that there is significant depletion of TEC, in some cases greater than 20% compared to other normal days. Observing the values of TEC before, during, and after the event, our study showed an apparent variation during the time of the eclipse, which agrees with previous studies on ionospheric responses to the eclipse as well as theoretical assumptions.

The solar eclipse effect on diffusion processes of O+ + O2 → O2+ + O reaction for the upper ionosphere over Kharkov

Abstract: The Sun is the most effective factor in determining all processes in the ionosphere. For this reason, examining the effect of solar eclipses on the earth ionosphere provides a very important source of information about sudden and medium-scale changes in the ionosphere structure during a solar eclipse. In this study, the effect of solar eclipse on March 29, 2006 in Kharkov on self-diffusion of O+ + O2 → O2+ + O reaction was investigated depending on the altitude (202, 252, and 303 km). As a result of the investigation, the minimum value of self-diffusion coefficient was seen at three altitudes on March 29, 2006 at the time of full covering in the solar. Self-diffusion coefficients were found to increase with increasing altitude. The results of the experimental study conducted to examine the effect of the eclipse on the ionosphere using high frequency wave propagation in Turkey where it was seen total eclipse on March 29, 2006 and the result that we obtained in this research are consistent with each other.

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.

Anatomy of the Annular Solar Eclipse of 26 December 2019 and Its Impact on Land– Atmosphere Interactions Over an Arid Region

Abstract: The impact of 26 December 2019 annular solar eclipse (ASE) on meteorological conditions over the southeastern Arabian Peninsula is investigated Observations sourced from the spinning enhanced visible and infrared imager (SEVIRI) and vertical temperature profiles measured by a microwave radiometer were used The ASE, which began at 03:36:379 Universal Time Coordinated (UTC), that is, 31 m 299 s after sunrise, left a significant imprint on the land surface temperature (LST) In particular, in some regions, the LST dropped by more than 4 °C, in comparison to the previous day In situ soil properties, in particular soil texture, were also found to have modulated the effects of the ASE, with loamy soils experiencing higher heating/cooling rates than sandy soils Finally, the analysis of atmospheric profiles indicated that the eclipse influenced the flow throughout the atmospheric boundary layer, with a stable layer that was 45-min longer and 90-m deeper compared with the preceding day

New Observations of the IR Emission Corona from the July 2, 2019 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 the Gulfstream V High-performance Instrumented Airborne Platform for Environmental Research (GV HIAPER), a 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, half of a density-sensitive S XI line pair, was detected for the first time. The 2017 AIR-Spec detection of Fe IX was confirmed and the first observations were made of the Fe IX intensity as a function of solar radius. Observations of S XI and Si X were used to estimate the temperature and density above the east and west limbs, the subject of a future paper. Atmospheric absorption was significant in the 2019 data, and atmospheric modeling was required to extract accurate line intensities. 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 flight. The thermal background was reduced by a factor of 30, providing a 5.5x improvement in signal-to-noise ratio, and the pointing stability was improved by a factor of five to $<$10 arcsec RMS after image co-alignment. In addition, two imaging artifacts were identified and resolved, making the 2019 data easier to interpret and improving the spectral resolution by up to 50%.

The 1875 British Solar Eclipse Expedition to Siam Led by Dr Arthur Schuster

Abstract: The total solar eclipse that took place on 6 April 1875 had a path of totality that passed through Siam, seven years after the famous 1868 total solar eclipse predicted by King Mongkut (Rama IV). The new King (Rama V) invited astronomers to his Kingdom to commemorate his father. In response, the Royal Society in Great Britain sent an eclipse expedition to Siam led by Dr (later Sir) Arthur Schuster. Expedition members met with the King and many influential personalities in Bangkok before traveling to the observatory site at Bang Thalu near Chulai Point in order to prepare for the eclipse. With help from officers and crew of H.M.S. Lapwing, as well as Europeans and Siamese from Bangkok and Phetchaburi, the observations were successful. Expedition members then went to Phetchaburi as guests of the Governor before returning for a longer stay in Bangkok. A second meeting with the King probably took place there. In this chapter, my recent search for the location of the 1875 observing site is also discussed.

The change of diffusion processes for O+ + N2 → NO+ + N reaction in the ionospheric F region during the solar eclipse over Kharkov

Abstract: Research on solar eclipses has been a very importance in detecting short and medium-scale changes in the ionosphere. In this paper, the relationship between the changes in self-diffusion coefficients (SDC) of the O+ + N2 → NO+ + N reaction with the solar eclipse of March 29th, 2006 in Kharkov (49.6° N and 36.3° E) was investigated for 202, 252 and 303 km. The results of the research showed that self-diffusion coefficients increases with the increase of ionospheric altitude in each three days and the maximum diffusion value is reached at 303 km on 29th of March. It can be said that results of effects of solar eclipse in Turkey on ionosphere, results of the study of the experimental measurement and obtaining results of our study are consistent with one another.

Ionospheric perturbation during the South American total solar eclipse on 14th December 2020 revealed with the Chilean GPS eyeball

Abstract: The influence of the South American total solar eclipse of 14th December 2020 on the ionosphere is studied by using the continuous Chilean Global Positioning System (GPS) sites across the totality path. The totality path with eclipse magnitude 1.012 passed through the Villarrica (Lon. 72.2308°W and Lat. 39.2820°S) in south Chile during 14:41:02.0 UTC to 17:30:58.1 UTC and maximum occurred ~ 16:03:49.5 UTC around the local noon. The vertical total electron content (VTEC) derived by GPS sites across the totality path for two PRN’s 29 and 31 show almost 20–40% of reduction with reference to ambient values. The percentage reduction was maximum close to totality site and decreases smoothly on both sides of totality sites. Interestingly, the atmospheric gravity waves (AGWs) with a period ~ 30–60 min obtained using wavelet analysis of VTEC timeseries show the presence of strong AGWs at the GPS sites located north of the totality line. But the AGWs do not show any significant effect on the VTEC values to these sites. Our analysis suggests, possibly an interplay between variability in the background plasma density and eclipse-generated AGWs induced plasma density perturbation could explain the observations.

Observations and Modeling Studies of Solar Eclipse Effects on Oblique High Frequency Radio Propagation

Abstract: National Aeronautics and Space Administration (NASA)National Aeronautics & Space Administration (NASA) [NNX17AH70G]; National Science Foundation (NSF)National Science Foundation (NSF) [AGS-1552188, AGS-1341925, AGS-1934997, AGS-1341918, AGS-1935110]; Virginia Space Grant Consortium (VSGC) 2015-2016 Undergraduate Research Fellowship; 2017-2018 VSGC Graduate Research Fellowship; 2018-2019 VSGC Graduate Research Fellowship

On the Nature of Propagating Intensity Disturbances in Polar Plumes during the 2017 Total Solar Eclipse

Abstract: The propagating intensity disturbances (PIDs) in plumes are still poorly understood and their identity (magnetoacoustic waves or flows) remains an open question. We investigate PIDs in five plumes located in the northern polar coronal hole observed during the 2017 total solar eclipse. Three plumes are associated with coronal bright points, jets and macrospicules at their base (active plumes) and the other two plumes are not (quiet plumes). The electron temperature at the base of the plumes is obtained from the filter ratio of images taken with the X-ray Telescope on board Hinode and the passband ratio around 400 nm from an eclipse instrument, the Diagnostic Coronagraph Experiment (DICE). The phase speed (v_r), frequency (omega), and wavenumber (k) of the PIDs in the plumes are obtained by applying a Fourier transformation to the space-time (r-t plane) plots in images taken with the Atmospheric Imaging Assembly (AIA) in three different wavelength channels (171 A, 193 A, and 211 A). We found that the PIDs in the higher temperature AIA channels, 193 and 211 A, are faster than that of the cooler AIA 171 A channel. This tendency is more significant for the active plumes than the quiet ones. The observed speed ratio (~1.3) between the AIA 171 and 193 A channels is similar to the theoretical value (1.25) of a slow magnetoacoustic wave. Our results support the idea that PIDs in plumes represent a superposition of slow magnetoacoustic waves and plasma outflows that consist of dense cool flows and hot coronal jets.

Variation of Low-Frequency Time-Code Signal Field Strength during the Annular Solar Eclipse on 21 June 2020: Observation and Analysis.

Abstract: Due to the occlusion of the moon, an annular solar eclipse will have an effect on the ionosphere above the earth. The change of the ionosphere, for the low-frequency time-code signal that relies on it as a reflection medium for long-distance propagation, the signal field strength, and other parameters will also produce corresponding changes, which will affect the normal operation of the low-frequency time-code time service system. This paper selects the solar eclipse that occurred in China on 21 June 2020, and uses the existing measurement equipment to carry out experimental research on the low-frequency time-code signal. We measured and analyzed the signal field strength from 20 June 2020 to 23 June 2020, and combined solar activity data, ionospheric data, and geomagnetic data, and attempted to explore the reasons and rules of the change of signal parameters. The results showed that the field strength of the low-frequency time-code signal changed dramatically within a short time period, the max growth value can reach up to 17 dBμV/m and the variation trend yielded 'three mutations'. This change in signal field strength is probably due to the occurrence of a solar eclipse that has an effect on the ionosphere. When the signal propagation conditions change, the signal strength will also change accordingly.