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Jay M Pasachoff - One of the best experts on this subject based on the ideXlab platform.
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air temperature and humidity during the Solar Eclipses of 26 december 2019 and of 21 june 2020 in saudi arabia and in other Eclipses with similar environments
arXiv: Atmospheric and Oceanic Physics, 2020Co-Authors: Marcos A Penalozamurillo, Abouazza Elmhamdi, Jay M Pasachoff, Michael T Roman, Yu Liu, Z A Almostafa, A H Maghrabi, H A AltrabulsyAbstract:We report air temperature and humidity changes during the two Solar Eclipses of 26 December 2019, and of 21 June 2020, respectively, in the cities of Al-Hofuf and Riyadh in Saudi Arabia. During the December eclipse the Sun rose already eclipsed (91.53% of the area covered) while the June eclipse, although also annular in other places of the Arabian Peninsula, was just partial at Riyadh (area covered 72.80%). This difference apparently affected the observed response on the recorded variables of temperature, relative humidity (RH) and vapor pressure (VP) in the two events. Change in these variables went unnoticed for the first eclipse since it was within the natural variability of the day; yet for the other, they showed clearly some trend alterations, which we analyze and discuss. A decrease in temperature of 3.2 °C was detected in Riyadh; however, RH and VP showed an oscillation that we explain in the light of a similar effect reported in other Eclipses. We found a time lag of about 15 min measured from the eclipse central phase in this city. We made an inspection of related fluctuations and dynamics from the computed rates of the temporal variation of temperature and RH. Trying to identify the influence of Solar Eclipses in similar environments we have made a broad inter-comparison with other observations of these variables in the Near East, northern Africa and in the United States. We compare our results with results obtained by other authors working with the December eclipse but in the United Arab Emirates and Oman, which showed dissimilar results. These inter-comparisons show how effectively the lower atmosphere can respond to a Solar eclipse within a desert environment and others similar. As a preamble, a historical revision of temperature and humidity in the context of eclipse meteorology is also included.
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heliophysics at total Solar Eclipses
Nature Astronomy, 2017Co-Authors: Jay M PasachoffAbstract:Total Solar Eclipses are a unique opportunity to study the lower Solar corona where the Solar wind originates. This review presents the recent advancements in coronal science from Eclipses and the scientific and outreach plans for this year's totality.
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resource letter ose 1 observing Solar Eclipses
American Journal of Physics, 2017Co-Authors: Jay M Pasachoff, Andrew FraknoiAbstract:This Resource Letter provides a guide to the available literature, listing selected books, articles, and online resources about scientific, cultural, and practical issues related to observing Solar Eclipses. It is timely, given that a total Solar eclipse will cross the continental United States on August 21, 2017. The next total Solar eclipse path crossing the U.S. and Canada will be on April 8, 2024. In 2023, the path of annularity of an annular eclipse will cross Mexico, the United States, and Canada, with partial phases visible throughout those countries.
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Solar Eclipses observed from antarctica
Proceedings of the International Astronomical Union, 2012Co-Authors: Jay M PasachoffAbstract:Aspects of the Solar corona are still best observed during totality of Solar Eclipses, and other high-resolution observations of coronal active regions can be observed with radio telescopes by differentiation of occultation observations, as we did with the Jansky Very Large Array for the annular Solar eclipse of 2012 May 20 in the US. Totality crossing Antarctica included the eclipse of 2003 November 23, and will next occur on 2021 December 4; annularity crossing Antarctica included the eclipse of 2008 February 7, and will next occur on 2014 April 29. Partial phases as high as 87% coverage were visible and were imaged in Antarctica on 2011 November 25, and in addition to partial phases of the total and annular Eclipses listed above, partial phases were visible in Antarctica on 2001 July 2011, 2002 December 4, 2004 April 19, 2006 September 22, 2007 September 11, and 2009 January 26, and will be visible on 2015 September 13, 2016 September 1, 2017 February 26, 2018 February 15, and 2020 December 14. On behalf of the Working Group on Solar Eclipses of the IAU, the poster showed the Solar Eclipses visible from Antarctica and this article shows a subset (see www.Eclipses.info for the full set). A variety of investigations of the Sun and of the response of the terrestrial atmosphere and ionosphere to the abrupt Solar cutoff can be carried out at the future Eclipses, making the Antarctic observations scientifically useful.
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Solar Eclipses as an astrophysical laboratory
Nature, 2009Co-Authors: Jay M PasachoffAbstract:Observations of the Sun during total Eclipses have led to major discoveries, such as the existence of helium (from its spectrum), the high temperature of the corona (though the reason for the high temperature remains controversial), and the role of magnetic fields in injecting energy into—and trapping ionized gases within—stellar atmospheres. A new generation of ground-based eclipse observations reaches spatial, temporal and spectral-resolution domains that are inaccessible from space and therefore complement satellite studies.
Robert L. Comstock - One of the best experts on this subject based on the ideXlab platform.
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Spatial and temporal patterns of Solar Eclipses by Phobos on Mars
Journal of Geophysical Research, 2005Co-Authors: Bruce G. Bills, Robert L. ComstockAbstract:[1] The spatial and temporal patterns associated with motion of the shadow of Phobos across the surface of Mars are quite different than those associated with Solar Eclipses on Earth. We present a simple analysis of variations in the position, velocity, size, and shape of the shadow. Simple expressions give reasonably accurate depictions of the shadow motion, which mainly consists of a subdiurnal longitude cycle and an annual latitude cycle. Over most of each year, there are an average of 3.22 shadow transits per day. The duration of the shadow transit depends on latitude. It is maximum at the equator and is then 11.8% of the orbital synodic period. As the subSolar point moves north, the shadow moves south, and vice versa. There is a narrow band, centered on the equator of Mars, within which every point is eclipsed at least once during each semiannual eclipse season. Outside that band, the density of coverage decreases slowly with increasing distance from the equator, until the limiting latitudes are reached. During epochs, like the present, when the obliquity of Mars is in excess of 21.2°, there are portions of each year during which no Eclipses occur. As the obliquity increases beyond that transition value, the durations of the eclipse seasons decrease. The minimum possible eclipse season duration, expressed as a fraction of the Mars year, is the same as the maximum shadow transit duration, expressed as a fraction of the Phobos synodic period, since both ratios depend on the same geometry, which is essentially just the radius of the orbit of Phobos, compared to the radius of Mars.
B J Adekoya - One of the best experts on this subject based on the ideXlab platform.
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ionospheric f2 layer responses to total Solar Eclipses at low and mid latitude
Journal of Atmospheric and Solar-Terrestrial Physics, 2016Co-Authors: B J Adekoya, V U ChukwumaAbstract:Abstract In this article, we 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) mid-latitude ionosonde stations, which are within the obscuration percentage of 50–100% of the path of the total Solar Eclipses progression. Statistically, the diurnal changes in the F2 layer peak height hmF2 and electron density NmF2, as well as the latitudinal and hemispheric dependence and the contribution of both magnetic and Solar activities during the eclipse window were investigated. The estimation of the Solar ionizing radiation that remains unmasked during the eclipse window was as well carried out. Plasma diffusion processes dominate the F2 region plasma, and determine the height at which the F2 peak formed at mid-latitude. The electron density decreased during the eclipse window, closely following the variation in the local Solar radiation at the mid-latitude. However, at equatorial/low-latitude, the plasma distribution during total Solar eclipse depends on combine effect of Solar radiation and the background nighttime ionospheric irregularities mechanism. The uncertainty level of the estimated Solar ionizing radiation was E ( t ) and electron density justifies the latitudinal relationship. The increase in percentage deviation of electron density increases with latitude and delay time (∆ T ) in the northern hemisphere of the mid-latitude. Conversely, in the southern hemisphere the percentage deviation decreases with an increase in ∆ T and the latitude. The influence of the combined effect of Solar activity and magnetic disturbances cannot the overlooked during total Solar eclipse. At the eclipse shadow, the deviation increases with decreasing magnetic disturbances and Solar activity. During magnetic quiet conditions the variation in maximum NmF2/hmF2 on the eclipse day are more decrease/increase than the control day and overturned during the magnetic disturbed condition.
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ionospheric vertical plasma drift and electron density response during total Solar Eclipses at equatorial low latitude
Journal of Geophysical Research, 2015Co-Authors: B J Adekoya, V U Chukwuma, B W ReinischAbstract:The response of the vertical plasma drift (Vz) and the electron density (NmF2) during different Solar Eclipses was investigated. The diurnal values of the direct scaled measurement of F2 peak height and the one derived from M(3000) F2 data, acquired over an equatorial/low-latitude stations, have been used to determine the vertical plasma drift. The ionosphere during a Solar eclipse is significantly affected by the E × B vertical drift; the large depletion of electron density at low altitudes can be transported to high altitudes through the plasma vertical drift. The loss in ionization density during the eclipse phase decreases the electron density, which was accompanied by rapid increase in hmF2. This deviation in the NmF2 during eclipse compared to control days can be related to the increase in the loss rate due to recombination, as a result of reduction in thermal energy. However, the maximum reduction in NmF2 is not synchronous with the time of maximum totality but some minutes later. The differences in the Solar epochs may contribute to the observed relative changes in the ionospheric F2 region behavior during the eclipse window. Lastly, it is very difficult to separate the influence of magnetic disturbances from Solar eclipse. The deviation in NmF2 is higher during magnetic disturbed days than the quiet day. The reverse is the case for hmF2 observation. However, the NmF2 variation increases with an increase in Solar activity.
V U Chukwuma - One of the best experts on this subject based on the ideXlab platform.
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ionospheric f2 layer responses to total Solar Eclipses at low and mid latitude
Journal of Atmospheric and Solar-Terrestrial Physics, 2016Co-Authors: B J Adekoya, V U ChukwumaAbstract:Abstract In this article, we 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) mid-latitude ionosonde stations, which are within the obscuration percentage of 50–100% of the path of the total Solar Eclipses progression. Statistically, the diurnal changes in the F2 layer peak height hmF2 and electron density NmF2, as well as the latitudinal and hemispheric dependence and the contribution of both magnetic and Solar activities during the eclipse window were investigated. The estimation of the Solar ionizing radiation that remains unmasked during the eclipse window was as well carried out. Plasma diffusion processes dominate the F2 region plasma, and determine the height at which the F2 peak formed at mid-latitude. The electron density decreased during the eclipse window, closely following the variation in the local Solar radiation at the mid-latitude. However, at equatorial/low-latitude, the plasma distribution during total Solar eclipse depends on combine effect of Solar radiation and the background nighttime ionospheric irregularities mechanism. The uncertainty level of the estimated Solar ionizing radiation was E ( t ) and electron density justifies the latitudinal relationship. The increase in percentage deviation of electron density increases with latitude and delay time (∆ T ) in the northern hemisphere of the mid-latitude. Conversely, in the southern hemisphere the percentage deviation decreases with an increase in ∆ T and the latitude. The influence of the combined effect of Solar activity and magnetic disturbances cannot the overlooked during total Solar eclipse. At the eclipse shadow, the deviation increases with decreasing magnetic disturbances and Solar activity. During magnetic quiet conditions the variation in maximum NmF2/hmF2 on the eclipse day are more decrease/increase than the control day and overturned during the magnetic disturbed condition.
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ionospheric vertical plasma drift and electron density response during total Solar Eclipses at equatorial low latitude
Journal of Geophysical Research, 2015Co-Authors: B J Adekoya, V U Chukwuma, B W ReinischAbstract:The response of the vertical plasma drift (Vz) and the electron density (NmF2) during different Solar Eclipses was investigated. The diurnal values of the direct scaled measurement of F2 peak height and the one derived from M(3000) F2 data, acquired over an equatorial/low-latitude stations, have been used to determine the vertical plasma drift. The ionosphere during a Solar eclipse is significantly affected by the E × B vertical drift; the large depletion of electron density at low altitudes can be transported to high altitudes through the plasma vertical drift. The loss in ionization density during the eclipse phase decreases the electron density, which was accompanied by rapid increase in hmF2. This deviation in the NmF2 during eclipse compared to control days can be related to the increase in the loss rate due to recombination, as a result of reduction in thermal energy. However, the maximum reduction in NmF2 is not synchronous with the time of maximum totality but some minutes later. The differences in the Solar epochs may contribute to the observed relative changes in the ionospheric F2 region behavior during the eclipse window. Lastly, it is very difficult to separate the influence of magnetic disturbances from Solar eclipse. The deviation in NmF2 is higher during magnetic disturbed days than the quiet day. The reverse is the case for hmF2 observation. However, the NmF2 variation increases with an increase in Solar activity.
Yoichiro Hanaoka - One of the best experts on this subject based on the ideXlab platform.
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polarization of the corona observed during the 2017 and 2019 total Solar Eclipses
Solar Physics, 2021Co-Authors: Yoichiro Hanaoka, Yoshiaki Sakai, Koichi TakahashiAbstract:We carried out polarimetric observations of the white-light corona during the total Solar Eclipses that occurred on August 21, 2017, and July 2, 2019, and successfully obtained data at two different sites for both Eclipses. After eliminating the sky background, we derived the brightness, polarization brightness, and degree of polarization of the K+F corona from just above the limb to approximately 4 R⊙. Furthermore, we isolated the K- and F-coronas with a plausible degree of polarization of the K-corona. The field of view covering up to approximately 4 R⊙ enabled us to compare the derived brightness and polarization with a wide range of other observations. The results of the comparison show significant scatter; while some of the observations present very good coincidence with our results, others exhibit systematic discrepancy.
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polarization of the corona observed during the 2017 and 2019 total Solar Eclipses
arXiv: Solar and Stellar Astrophysics, 2021Co-Authors: Yoichiro Hanaoka, Yoshiaki Sakai, Koichi TakahashiAbstract:We carried out polarimetric observations of the white-light corona during the total Solar Eclipses that occurred on 2017 August 21 and 2019 July 2, and successfully obtained data at two different sites for both Eclipses. After eliminating the sky background, we derived the brightness, polarization brightness, and degree of the polarization of the K+F corona from just above the limb to approximately 4 $R_\odot$. Furthermore, we isolated the K- and F-corona with plausible degree of polarization of the K-corona. The field of view covering up to approximately 4 $R_\odot$ enabled us to compare the derived brightness and polarization with a wide range of other observations. The results of the comparison show significant scatter; while some of the observations present very good coincidence with our results, the other ones exhibit systematic discrepancy.
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Accurate Measurements of the Brightness of the White-Light Corona at the Total Solar Eclipses on 1 August 2008 and 22 July 2009
Solar Physics, 2012Co-Authors: Yoichiro Hanaoka, Yoshihiro Kikuta, Jun Nakazawa, Kouji Ohnishi, Kazuo ShiotaAbstract:We measured the brightness of the white light corona at the total Solar Eclipses on 1 August 2008 and 22 July 2009, when Solar activity was at its lowest in one hundred years. After careful calibration, the brightness of the corona in both Eclipses was evaluated to be approximately 0.4×10^−6 of the total brightness of the Sun, which is the lowest level ever observed. Furthermore, the total brightness of the K+F-corona beyond 3 R _⊙ in both Eclipses is lower than some of the previous measurements of the brightness of the F-corona only. Our accurate measurements of the coronal brightness provide not only the K-corona brightness during a period of very low Solar activity but also a reliable upper limit of the brightness of the F-corona.