Showing papers on "Solar eclipse published in 2016"
TL;DR: Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse are reviewed, with particular attention to events providing important early insights into the ionization of the upper atmosphere.
Abstract: This article reviews atmospheric changes associated with 44 solar eclipses, beginning with the first quantitative results available, from 1834 (earlier qualitative, accounts also exist). Eclipse meteorology attracted relatively few publications until the total solar eclipse of 16 February 1980, with the 11 August 1999 eclipse producing the most papers. Eclipses passing over populated areas such as Europe, China and India now regularly attract scientific attention, whereas atmospheric measurements of eclipses at remote locations remain rare. Many measurements and models have been used to exploit the uniquely predictable solar forcing provided by an eclipse. In this paper we compile the available publications and review a sub-set of them chosen on the basis of importance and novelty. Beyond the obvious reduction in incoming solar radiation, atmospheric cooling from eclipses can induce dynamical changes. Observations and meteorological modelling provide evidence for the generation of a local eclipse circulation which may be the origin of the "eclipse wind". Gravity waves set up by the eclipse can, in principle, be detected as atmospheric pressure fluctuations, though theoretical predictions are limited, and many of the data are inconclusive. Eclipse events providing important early insights into the ionisation of the upper atmosphere are also briefly reviewed.
42 citations
TL;DR: This article reviewed atmospheric changes associated with 44 solar eclipses, beginning with the first quantitative results available, from 1834, and reviewed a subset of them chosen on the basis of importance and novelty.
Abstract: This article reviews atmospheric changes associated with 44 solar eclipses, beginning with the first quantitative results available, from 1834 (earlier qualitative accounts also exist). Eclipse meteorology attracted relatively few publications until the total solar eclipse of 16 February 1980, with the 11 August 1999 eclipse producing the most papers. Eclipses passing over populated areas such as Europe, China and India now regularly attract scientific attention, whereas atmospheric measurements of eclipses at remote locations remain rare. Many measurements and models have been used to exploit the uniquely predictable solar forcing provided by an eclipse. In this paper, we compile the available publications and review a subset of them chosen on the basis of importance and novelty. Beyond the obvious reduction in incoming solar radiation, atmospheric cooling from eclipses can induce dynamical changes. Observations and meteorological modelling provide evidence for the generation of a local eclipse circulation that may be the origin of the ‘eclipse wind’. Gravity waves set up by the eclipse can, in principle, be detected as atmospheric pressure fluctuations, though theoretical predictions are limited, and many of the data are inconclusive. Eclipse events providing important early insights into the ionization of the upper atmosphere are also briefly reviewed. This article is part of the themed issue ‘Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse’.
35 citations
TL;DR: In this article, the influence of variable production of photovoltaic plants on the synchronous continental Europe interconnection during the solar eclipse of March 20, 2015 is analyzed. And the results of long-term dynamic simulations focus on frequency stability (taking into account daily load diagram, secondary and primary frequency control, system inertia, settings of frequency protections and load frequency shedding).
Abstract: This paper analyses the influence of variable production of photovoltaic plants on the synchronous continental Europe interconnection during the solar eclipse of March 20, 2015. For countries with a high share of photovoltaics, the daily photovoltaics generation is estimated for the worst-case scenario – a clear sunny day. The presented results of long-term dynamic simulations focus on frequency stability (taking into account daily load diagram, secondary and primary frequency control, system inertia, settings of frequency protections and load frequency shedding).
32 citations
TL;DR: Air temperature, mean sea-level pressure, wind speed and direction and cloud-cover data acquired during the solar eclipse of 20 March 2015 from 76 UK Met Office weather stations are compared with those from 30 weather stations in the Faroe Islands and 148 stations in Iceland, and there is no evidence of an eclipse cyclone over Britain.
Abstract: Here, we analyse high-frequency (1 min) surface air temperature, mean sea-level pressure (MSLP), wind speed and direction and cloud-cover data acquired during the solar eclipse of 20 March 2015 from 76 UK Met Office weather stations, and compare the results with those from 30 weather stations in the Faroe Islands and 148 stations in Iceland. There was a statistically significant mean UK temperature drop of 0.83±0.63°C, which occurred over 39 min on average, and the minimum temperature lagged the peak of the eclipse by about 10 min. For a subset of 14 (16) relatively clear (cloudy) stations, the mean temperature drop was 0.91±0.78 (0.31±0.40)°C but the mean temperature drops for relatively calm and windy stations were almost identical. Mean wind speed dropped significantly by 9% on average during the first half of the eclipse. There was no discernible effect of the eclipse on the wind-direction or MSLP time series, and therefore we can discount any localized eclipse cyclone effect over Britain during this event. Similar changes in air temperature and wind speed are observed for Iceland, where conditions were generally clearer, but here too there was no evidence of an eclipse cyclone; in the Faroes, there was a much more muted meteorological signature.This article is part of the themed issue 'Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse'.
31 citations
TL;DR: In this article, the ionospheric behavior over Belgium during the partial solar eclipse of 20 March 2015 is analyzed based on high-resolution solar radio flux, vertical incidence sounding, and GPS TEC measurements.
30 citations
TL;DR: A modern approach to ‘eclipse meteorology’ as identified here can ultimately improve weather prediction models and be used to plan for transient reductions in renewable electricity generation.
Abstract: A solar eclipse provides a well-characterized reduction in solar radiation, of calculable amount and duration. This captivating natural astronomical phenomenon is ideally suited to science outreach activities, but the predictability of the change in solar radiation also provides unusual conditions for assessing the atmospheric response to a known stimulus. Modern automatic observing networks used for weather forecasting and atmospheric research have dense spatial coverage, so the quantitative meteorological responses to an eclipse can now be evaluated with excellent space and time resolution. Numerical models representing the atmosphere at high spatial resolution can also be used to predict eclipse-related changes and interpret the observations. Combining the models with measurements yields the elements of a controlled atmospheric experiment on a regional scale (10-1000 km), which is almost impossible to achieve by other means. This modern approach to 'eclipse meteorology' as identified here can ultimately improve weather prediction models and be used to plan for transient reductions in renewable electricity generation. During the 20 March 2015 eclipse, UK electrical energy demand increased by about 3 GWh (11 TJ) or about 4%, alongside reductions in the wind and photovoltaic electrical energy generation of 1.5 GWh (5.5 TJ).This article is part of the themed issue 'Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse'.
25 citations
TL;DR: It is concluded that the complex synoptic weather conditions over the UK at the time of this particular eclipse helped to mask any eclipse-driven gravity waves.
Abstract: Internal gravity waves are generated as adjustment radiation whenever a sudden change in forcing causes the atmosphere to depart from its large-scale balanced state. Such a forcing anomaly occurs during a solar eclipse, when the Moon’s shadow cools part of the Earth’s surface. The resulting atmospheric gravity waves are associated with pressure and temperature perturbations, which in principle are detectable both at the surface and aloft. In this study, surface pressure and temperature data from two UK sites at Reading and Lerwick are examined for eclipse-driven gravity wave perturbations during the 20 March 2015 solar eclipse over northwest Europe. Radiosonde wind data from the same two sites are also analysed using a moving parcel analysis method, to determine the periodicities of the waves aloft. On this occasion, the perturbations both at the surface and aloft are found not to be confidently attributable to eclipse-driven gravity waves. We conclude that the complex synoptic weather conditions over the UK at the time of this particular eclipse helped to mask any eclipse-driven gravity waves. This article is part of the themed issue ‘Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse’.
25 citations
TL;DR: In this article, the authors analyzed the behavior of total ionospheric ionization over Europe by reconstructing total electron content (TEC) maps and differential TEC maps and found that the magnitude of TEC depletion is linearly dependent on the Sun's obscuration function.
Abstract: The solar eclipse on March 20, 2015 was a fascinating event for people in Northern Europe. From a scientific point of view, the solar eclipse can be considered as an in situ experiment on the Earth’s upper atmosphere with a well-defined switching off and on of solar irradiation. Due to the strong changes in solar radiation during the eclipse, dynamic processes were initiated in the atmosphere and ionosphere causing a measurable impact, for example, on temperature and ionization. We analyzed the behavior of total ionospheric ionization over Europe by reconstructing total electron content (TEC) maps and differential TEC maps. Investigating the large depletion zone around the shadow spot, we found a TEC reduction of up to 6 TEC units, i.e., the total plasma depletion reached up to about 50%. However, the March 20, 2015 eclipse occurred during the recovery phase of a strong geomagnetic storm and the ionosphere was still perturbed and depleted. Therefore, the unusual high depletion is due to the negative bias of up to 20% already observed over Northern Europe before the eclipse occurred. After removing the negative storm effect, the eclipse-induced depletion amounts to about 30%, which is in agreement with previous observations. During the solar eclipse, ionospheric plasma redistribution processes significantly affected the shape of the electron density profile, which is seen in the equivalent slab thickness derived by combining vertical incidence sounding (VS) and TEC measurements. We found enhanced slab thickness values revealing, on the one hand, an increased width of the ionosphere around the maximum phase and, on the other, evidence for delayed depletion of the topside ionosphere. Additionally, we investigated very low frequency (VLF) signal strength measurements and found immediate amplitude changes due to ionization loss at the lower ionosphere during the eclipse time. We found that the magnitude of TEC depletion is linearly dependent on the Sun’s obscuration function. By modelling TEC depletion and knowing the Sun’s obscuration function in advance, Global Navigation Satellite System (GNSS) operators may improve the broadcast ionospheric correction during a solar eclipse day.
25 citations
TL;DR: In this article, the authors estimate D region changes due to 22 July 2009 total solar eclipse (SE), 13-14 November 2012 total SE, and 9-10 May 2013 annular SE, using VLF navigational transmitters signal observations at Suva, Fiji.
Abstract: We estimate D region changes due to 22 July 2009 total solar eclipse (SE), 13–14 November 2012 total SE, and 9–10 May 2013 annular SE, using VLF navigational transmitters signal observations at Suva, Fiji The North West Cape (NWC) signal (198 kHz) showed an amplitude and phase decrease of 070 dB and 23° during November SE and 20 dB and 90° during May SE The modeling using Long Wave Propagation Capability code for NWC-Suva path during November and May SEs showed an increase in average D region reflection height (H′) and sharpness factor (β) by 06 and 05 km and 0012 and 0015 km−1, respectively The July total SE for JJI-Suva path showed an increase in H′ of 15 km and a decrease in β of 0055 km−1 The decrease in the electron density calculated using SE time H′ and β is maximum for July total SE and minimum for May annular SE The effective recombination coefficient estimated from the decay and recovery of signal phase associated with May annular SE was higher (27%) than normal daytime value 50 × 10−7 cm−3 s−1 and varied between 147 × 10−6 and 115 × 10−7 cm−3 s−1 in the altitude 70 to 80 km Morlet wavelet analysis of signals amplitude shows strong wave-like signatures (WLS) associated with three SEs with period ranging 24–66 min, but the intensity and duration of WLS show no clear dependence on SE magnitude and type Apart from the cooling spot, the eclipse shadow can also generate WLS associated with atmospheric gravity waves
22 citations
TL;DR: The British Isles benefits from dense meteorological observation networks, enabling insights into the still-unresolved effects of solar eclipse events on the near-surface wind field, and a new explanation is proposed here by analogy with nocturnal wind changes at sunset and shown to predict direction changes consistent with those observed.
Abstract: The British Isles benefits from dense meteorological observation networks, enabling insights into the still-unresolved effects of solar eclipse events on the near-surface wind field. The near-surfa...
21 citations
TL;DR: In this article, the authors investigated the variation in the Global Positioning System (GPS) derived ionospheric Total Electron Content (TEC) over Equatorial Ionization Anomaly (EIA) region on the rare occasional astronomical phenomenon of total solar eclipse of 22 July 2009.
TL;DR: In this article, the authors used wavelet analysis to study the periodic variations in intensity, Doppler velocity, and line width using multislit spectroscopic observations of the solar corona.
Abstract: During the total solar eclipse of 11 July 2010, multi-slit spectroscopic observations of the solar corona were performed from Easter Island, Chile. To search for high-frequency waves, observations were taken at a high cadence in the green line at 5303 A that is due to [Fe xiv] and the red line at 6374 A that is due to [Fe x]. The data were analyzed to study the periodic variations in intensity, Doppler velocity, and line width using wavelet analysis. The data with high spectral and temporal resolution enabled us to study the rapid dynamical changes within coronal structures. We find that at certain locations, each parameter shows significant oscillation with periods ranging from 6 – 25 s. For the first time, we were able to detect damping of high-frequency oscillations with periods of about 10 s. If the observed damped oscillations are due to magnetohydrodynamic waves, then they can contribute significantly to the heating of the corona. From a statistical study we try to characterize the nature of the observed oscillations while considering the distribution of power in different line parameters.
TL;DR: In this article, the authors describe the construction of the photovoltaic (PV) system and show the unique data measured during the solar eclipse on the 20th of March 2015.
TL;DR: In this article, the authors presented ionospheric F2 responses to total solar eclipses on the basis of the data obtained from five (5) equatorial/low-latitude and twenty-seven (27) midlatitude ionosonde stations, which are within the obscuration percentage of 50-100% of the path of the total solar eclipse progression.
TL;DR: In this article, the authors highlight how the availability of measurements autoscaled at some reference ionospheric stations, and their assimilation by ionosphere models, was of crucial importance in determining, during the solar eclipse conditions occurred on 20 March 2015, a reliable representation of the ionosphere.
TL;DR: Transporting the sensors aloft using standard meteorological instrument packages modified to carry extra sensors, providing one promising but hitherto unexploited possibility for making solar eclipse radiation measurements, gives values that agree with theoretical expectations for the eclipse-induced radiation changes.
Abstract: Solar eclipses provide a rapidly changing solar radiation environment. These changes can be studied using simple photodiode sensors, if the radiation reaching the sensors is unaffected by cloud.Transporting the sensors aloft using standard meteorological instrument packages modified to carry extra sensors, provides one promising but hitherto unexploited possibility for making solar eclipse radiation measurements. For the 20th March 2015 solar eclipse, a coordinated campaign of balloon-carried solar radiation measurements was undertaken from Reading (51.44N, 0.94W), Lerwick (60.15N, 1.13W) and Reykjavik (64.13N, 21.90W), straddling the path of the eclipse.The balloons reached sufficient altitude at the eclipse time for eclipse-induced variations in solar radiation and solar limb darkening to be measured above cloud. Because the sensor platforms were free to swing, techniques have been evaluated to correct the measurements for their changing orientation. In the swing-averaged technique, the mean value across a set of swings was used to approximate the radiation falling on a horizontal surface; in the swing-maximum technique, the direct beam was estimated by assuming the sensing surface becomes normal to the solar beam direction at a maximum swing. Both approaches, essentially independent,give values that agree with theoretical expectations for the eclipse-induced radiation changes.
TL;DR: Ionospheric disturbances at an altitude of 300 km that accompanied the solar eclipse of March 20, 2015, have been analyzed based on the ionosondes located in Europe as discussed by the authors.
Abstract: Ionospheric disturbances at an altitude of 300 km that accompanied the solar eclipse of March 20, 2015, have been analyzed based on the ionosondes located in Europe. It has been confirmed that the eclipse was accompanied by the generation of gravity waves in the neutral atmosphere and traveling ionospheric disturbances. The period of the latter was 30–100 min, and the amplitude of relative electron density disturbances was 4–19%. The disturbances continued for not less than 2 h. During the eclipse, the disturbance amplitude more frequently increased. It decreased in one case, since the wave process observed previously was suppressed by the process generated by the eclipse.
TL;DR: By comparing the results of the NEWEx analyses with results from other investigations of the same eclipse using different observational networks, including measurements from the University of Reading’s Atmospheric Observatory, it is demonstrated that NEWEx provided a fair representation of the change in the UK meteorological conditions throughout the eclipse.
Abstract: The National Eclipse Weather Experiment (NEWEx) was a citizen science project designed to assess the effects of the 20 March 2015 partial solar eclipse on the weather over the United Kingdom (UK). NEWEx had two principal objectives: to provide a spatial network of meteorological observations across the UK to aid the investigation of eclipse induced weather changes; and to develop a nationwide public engagement activity based participation of citizen scientists. In total NEWEx collected 15606 observations of air temperature, cloudiness, and wind speed and direction from 309 locations across the UK, over a 3 hour window spanning the eclipse period. The headline results were processed in near real-time, immediately published on-line,
and featured in UK national press articles on the day of the eclipse. Here we describe the technical development of NEWEx and how the observations provided by the citizen scientists were analysed. By comparing the results of the NEWEx analyses with results from other investigations of the same eclipse using different observational networks, including measurements from the University of Reading’s Atmospheric Observatory, we demonstrate that NEWEx provided a fair representation of the change in the UK meteorological conditions throughout the eclipse. Despite the simplicity of the approach adopted, robust reductions in both temperature and wind speed during the eclipse were observed.
TL;DR: In this mid-morning eclipse, the topographical influences on NSAT anomalies were apparently dominated by variations in residual nocturnal inversion strength, as suggested by significant correlations between post-sunrise temperature and NSAT anomaly at clear-sky sites (larger negative anomalies with lower post-Sunrise temperatures).
Abstract: Near-surface air temperature (NSAT) anomalies during the 20 March 2015 solar eclipse are investigated at 266 UK sites, using operational data. The high density of observing sites, together with the wide range of ambient meteorological conditions, provided an unprecedented opportunity for analysis of the spatial variability of NSAT anomalies under relatively uniform eclipse conditions. Anomalies ranged from −0.03°C to −4.23°C (median −1.02°C). The maximum (negative) anomaly lagged the maximum obscuration by 15 min on average. Cloud cover impacted strongly on NSAT anomalies, with larger anomalies in clear-sky situations ( p This article is part of the themed issue ‘Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse’.
TL;DR: This study covers the largest area and uses the most observations of eclipse-induced surface temperature drops to date, and is the first full characterization of satellite LST during an eclipse, which could be applied to Geostationary Operational Environmental Satellite (GOES) LST data over North America during the August 2017 total solar eclipse.
Abstract: The behaviour of remotely sensed land surface temperatures (LSTs) from the spinning-enhanced visible and infrared imager (SEVIRI) during the total solar eclipse of 20 March 2015 is analysed over Europe. LST is found to drop by up to several degrees Celcius during the eclipse, with the minimum LST occurring just after the eclipse mid-point (median=+1.5 min). The drop in LST is typically larger than the drop in near-surface air temperatures reported elsewhere, and correlates with solar obscuration ( r =−0.47; larger obscuration = larger LST drop), eclipse duration ( r =−0.62; longer duration = larger LST drop) and time ( r =+0.37; earlier eclipse = larger LST drop). Locally, the LST drop is also correlated with vegetation (up to r =+0.6), with smaller LST drops occurring over more vegetated surfaces. The LSTs at locations near the coast and at higher elevation are also less affected by the eclipse. This study covers the largest area and uses the most observations of eclipse-induced surface temperature drops to date, and is the first full characterization of satellite LST during an eclipse (known to the author). The methods described could be applied to Geostationary Operational Environmental Satellite (GOES) LST data over North America during the August 2017 total solar eclipse. This article is part of the themed issue ‘Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse’.
TL;DR: The National Eclipse Weather Experiment (NEWEx) was a citizen science project for atmospheric data collection from the partial solar eclipse of 20 March 20, and its role as a tool for schools outreach is discussed here, in seeking to bridge the gap between self-identification with the role of a scientist and engagement with science, technology, engineering and mathematics subjects.
Abstract: The National Eclipse Weather Experiment (NEWEx) was a citizen science project for atmospheric data collection from the partial solar eclipse of 20 March 20. Its role as a tool for schools outreach ...
TL;DR: In this paper, the results of measuring HF signals on oblique chirp sounding paths in the Eurasian region during a solar eclipse of March 20, 2015 and the neighboring days are presented.
Abstract: The results of measuring HF signals on oblique chirp sounding paths in the Eurasian region during a solar eclipse of March 20, 2015 and the neighboring days are presented. The solar eclipse took place against the background of a strong magnetic storm. It was established that during the solar eclipse on oblique sounding paths of different length and orientation the decrease in the maximum observable frequency for the F mode (MOF-F) and the lowest observable frequency for the F mode (LOF-F) was 8–14% and 22–33%, respectively. During the eclipse, the signal amplitude increased by 3–5 dB. On the Lovozero—Nizhny Novgorod path in the maximum phase of the solar eclipse, the electron density decrease in the ionospheric E and F2 layers at the midpoint of the path reached 37% and 22%, respectively. According to the MOF and LOF variation measurements for various modes, the group delay time of radio signals, and the results of spectral analysis, it was found that in the eclipse there were wave disturbances with a period of 25 to 50 min. However, quasi-periodic variations of MOF-F and LOF-F having a a period of 50 to 80 min but which started before the eclipse were detected on some paths. Probably, in these cases, the variations were a result of the superposition of disturbances from two sources, namely, the magnetic storm and the solar eclipse.
TL;DR: In this paper, the authors used the Rossiter-McLaughlin (RM) effect during a solar eclipse and the high precision of solar radial velocities (RVs) for spectral line formation.
Abstract: Spectroscopic observations of a solar eclipse can provide unique information for solar and exoplanet research; the huge amplitude of the Rossiter-McLaughlin (RM) effect during solar eclipse and the high precision of solar radial velocities (RVs) allow detailed comparison between observations and RV models, and they provide information about the solar surface and about spectral line formation that are otherwise difficult to obtain. On March 20, 2015, we obtained 159 spectra of the Sun as a star with the solar telescope and the Fourier Transform Spectrograph at the Institut fur Astrophysik Gottingen, 76 spectra were taken during partial solar eclipse. We obtained RVs using I 2 as wavelength reference and determined the RM curve with a peak-to-peak amplitude of almost 1.4 km s-1 at typical RV precision better than 1 m s-1 . We modeled the disk-integrated solar RVs using well-determined parameterizations of solar surface velocities, limb darkening, and information about convective blueshift from 3D magnetohydrodynamic simulations. We confirm that convective blueshift is crucial to understand solar RVs during eclipse. Our best model reproduced the observations to within a relative precision of 10% with residuals lower than 30 m s-1 . We cross-checked parameterizations of velocity fields using a Dopplergram from the Solar Dynamics Observatory and conclude that disk-integration of the Dopplergram does not provide correct information about convective blueshift necessary for m s-1 RV work. As main limitation for modeling RVs during eclipses, we identified limited knowledge about convective blueshift and line shape as functions of solar limb angle. We suspect that our model line profiles are too shallow at limb angles larger than μ = 0.6, resulting in incorrect weighting of the velocities across the solar disk. Alternative explanations cannot be excluded, such as suppression of convection in magnetic areas and undiscovered systematics during eclipse observations. To make progress, accurate observations of solar line profiles across the solar disk are suggested. We publish our RVs taken during solar eclipse as a benchmark curve for codes calculating the RM effect and for models of solar surface velocities and line profiles.
TL;DR: In this article, the effects of the solar eclipse on the behavior of grid connected photovoltaic (PV) systems have been evaluated in order to monitor the impact of this natural phenomenon on the behaviour of PV system and these results are presented in the paper.
Abstract: PV power plants have been recently installed in very large scale. So the effects of the solar eclipse are of big importance especially for grid connected photovoltaic (PV) systems. There was a partial solar eclipse in Prague on 20th March 2015. We have evaluated the data from our facility in order to monitor the impact of this natural phenomenon on the behavior of PV system, and these results are presented in the paper. The behavior of PV system corresponds with the theoretical assumption. The power decrease of the PV array corresponds with the relative size of the solar eclipse. - characteristics of the PV panel correspond to the theoretical model presented in our previous work.
TL;DR: In this paper, the authors present the peculiarities of the radiation components and basic meteorology observed during the eclipse event, as well as a supplementary data set containing the basic BSRN radiation and surface meteorological data in 1min resolution for March 2015.
Abstract: . On 20 March 2015, a total solar eclipse occurred over Ny-Alesund (78.9° N, 11.9° E), Svalbard, in the high Arctic. It was the first time that the surface radiation components during the totality of a solar eclipse were measured by a Baseline Surface Radiation Network (BSRN) station. With the Ny-Alesund long-term radiation data set as background (available at doi:10.1594/PANGAEA.150000 ), we present here the peculiarities of the radiation components and basic meteorology observed during the eclipse event. The supplementary data set contains the basic BSRN radiation and surface meteorological data in 1 min resolution for March 2015, and is available at doi:10.1594/PANGAEA.854326 . The eclipse radiation data will be a useful auxiliary data set for further studies on micrometeorological surface–atmosphere exchange processes in the Svalbard environment, and may serve as a test case for radiative transfer studies.
TL;DR: In this paper, the authors discuss how Amazonia was introduced to Einstein's theory of gravitation and also the observations and repercussions of the May 29, 1919, solar eclipse in Belem, capital city of the North-Brazilian Para state.
Abstract: In 1919, A. C. D. Crommelin and C. R. Davidson, British astronomers from the Greenwich Observatory in England, passed by Amazonia on their Brazilian journey aiming to measure the bending of stars' light rays during the total solar eclipse of May 29, 1919, and thereby put the theory of general relativity to the test. In the context of Crommelin’s and Davidson’s visit, we discuss how Amazonia was introduced to Einstein’s theory of gravitation, and also the observations and repercussions of the May 29, 1919, solar eclipse in Belem, capital city of the North-Brazilian Para state.
TL;DR: In this article, the effects of the total solar eclipse on the VLF signal were investigated using the knowledge of the lower ionospheric chemical and physical properties, which is not well studied till date.
Abstract: The variation in the solar Extreme Ultraviolet (EUV) radiation flux by any measure is the most dominant natural source to produce perturbations or modulations in the ionospheric chemical and plasma properties. A solar eclipse, though a very rare phenomenon, is similarly bound to produce a significant short time effect on the local ionospheric properties. The influence of the ionizing solar flux reduction during a solar eclipse on the lower ionosphere or, more precisely, the D-region, can be studied with the observation of Very Low Frequency (VLF) radio wave signal modulation. The interpretation of such an effect on VLF signals requires a knowledge of the D-region ion chemistry, which is not well studied till date. Dominant parameters which govern the ion chemistry, such as the recombination coefficients, are poorly known. The occurrence of events such as a solar eclipse provides us with an excellent opportunity to investigate the accuracy of our knowledge of the chemical condition in this part of Earth’s atmosphere and the properties which control the ionospheric stability under such disturbances. In this paper, using existing knowledge of the lower ionospheric chemical and physical properties we carry out an interpretation of the effects obtained during the total solar eclipse of 22 of July 2009 on the VLF signal. Data obtained from a week long campaign conducted by the Indian Centre for Space Physics (ICSP) over the Indian subcontinent has been used for this purpose. Both positive and negative amplitude changes during the eclipse were observed along various receiver locations. In this paper, data for a propagation path between a Indian Navy VLF transmitter named VTX3 and a pair of receivers in India are used. We start from the observed solar flux during the eclipse and calculate the ionization during the whole time span over most of the influenced region in a range of height. We incorporate a D-region ion-chemistry model to find the equilibrium ion density over the region and employ the LWPC code to find the VLF signal amplitude. To tackle the uncertainty in the values of the recombination coefficients we explore a range of values in the chemical evolution model. We achieve two goals by this exercise: First, we have been able to reproduce the trends, if not the exact signal variation, of the VLF signal modulations during a solar eclipse at two different receiving stations with sufficient accuracy purely from theoretical modeling, and second our knowledge of some of the D-region ion-chemistry parameters is now improved.
01 Nov 2016
TL;DR: In this article, a Sky Quality Meter (SQM) was employed to measure the sky brightness during the 2016 total solar eclipse, which is shown by the SQM value of zero.
Abstract: Obscuration of the Sun by the Moon during total solar eclipse generates the changing of the sky brightness. Sky Quality Meter (SQM) was employed to measure the sky brightness during the 2016 total solar eclipse. The sky was still bright at the first contact time. It is shown by the SQM value of zero. Approaching the second contact time, the SQM value is rising up started at the value of 5.92 mpsas. The curvature profile of the SQM measurementvalue is similar to the curvature profile of the SQM measurement at the dawn and dusk. However, the flatness part of the curvature is much shorter than night time value of SQM. The maximum of SQM measurement value is lower than the SQM measurement value during the night in Ternate. It is 12.47 mpsas and happened at the maximum phase of the eclipse. It was confirmed by the fact that at the time of totality, the sky close to the horizon was still bright. There is a discrepancy between the predicted and actual second and third contact and maximum eclipse time. By assigning the maximum of SQM measurement value as the reference value of maximum eclipse time, the actual second and third time can be calculated. The shape of curvature between the actual second and third contact time is symmetry.
TL;DR: The near-surface atmospheric response at the High Arctic site of Svalbard is reported as a result of abrupt changes in solar insolation during the 20 March 2015 equinox total solar eclipse and notifies the atmospheric science community of the availability of a rare dataset.
Abstract: This article reports on the near-surface atmospheric response at the High Arctic site of Svalbard, latitude 78° N, as a result of abrupt changes in solar insolation during the 20 March 2015 equinox total solar eclipse and notifies the atmospheric science community of the availability of a rare dataset. Svalbard was central in the path of totality, and had completely clear skies. Measurements of shaded air temperature and atmospheric pressure show only weak, if any, responses to the reduced insolation. A minimum in the air temperature at 1.5 m above the ground occurred starting 2 min following the end of totality, though this drop was only slightly beyond the observed variability for the midday period. Eclipse-produced variations in surface pressure, if present, were less than 0.3 hPa.
TL;DR: In this article, the authors obtained 159 spectra of the Sun as a star with the solar telescope and the FTS at the Institut fur Astrophysik Gottingen, 76 spectra were taken during a partial solar eclipse.
Abstract: On March 20, 2015, we obtained 159 spectra of the Sun as a star with the solar telescope and the FTS at the Institut fur Astrophysik Gottingen, 76 spectra were taken during partial solar eclipse. We obtained RVs using $I_2$ as wavelength reference and determined the RM curve with a peak-to-peak amplitude of almost 1.4 km s$^{-1}$ at typical RV precision better than 1 m s$^{-1}$. We modeled disk-integrated solar RVs using surface velocities, limb darkening, and information about convective blueshift from 3D magneto-hydrodynamic simulations. We confirm that convective blueshift is crucial to understand solar RVs during eclipse. Our best model reproduced the observations to within a relative precision of 10% with residuals less than 30 m s$^{-1}$. We cross-checked parameterizations of velocity fields using a Dopplergram from the Solar Dynamics Observatory and conclude that disk-integration of the Dopplergram does not provide correct information about convective blueshift necessary for m s$^{-1}$ RV work. As main limitation for modeling RVs during eclipses, we identified limited knowledge about convective blueshift and line shape as functions of solar limb angle. We suspect that our model line profiles are too shallow at limb angles larger than $\mu = 0.6$ resulting in incorrect weighting of the velocities across the solar disk. Alternative explanations cannot be excluded like suppression of convection in magnetic areas and undiscovered systematics during eclipse observations. Accurate observations of solar line profiles across the solar disk are suggested. We publish our RVs taken during solar eclipse as a benchmark curve for codes calculating the RM effect and for models of solar surface velocities and line profiles.