Sky Brightness and Polarization During the 1973 African Eclipse

Shaw, Glenn E.

doi:10.1364/ao.14.000388

Cited by 35 publications

(29 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For diffuse irradiance the ratio decreases continuously from about 8500 at 330 nm to 2100 at 500 nm and for radiance from 9500 at 330 nm to 3700 at 500 nm. The order of magnitude of those calculations is comparable to the results obtained by Shaw (1975) and to the measurements described in Silverman and Mullen (1975); Sharp et al (1971).…”

Section: Radiance and Irradiance Spectrasupporting

confidence: 86%

Simulation of solar radiation during a total eclipse: a challenge for radiative transfer

2007

View full text Add to dashboard Cite

Abstract.A solar eclipse is a rare but spectacular natural phenomenon and furthermore it is a challenge for radiative transfer modelling. Whereas a simple one-dimensional radiative transfer model with reduced solar irradiance at the top of the atmosphere can be used to calculate the brightness during partial eclipses a much more sophisticated model is required to calculate the brightness (i.e. the diffuse radiation) during the total eclipse. The reason is that radiation reaching a detector in the shadow gets there exclusively by horizontal transport of photons in a spherical shell atmosphere, which requires a three-dimensional radiative transfer model. In this study the first fully three-dimensional simulations for a solar eclipse are presented exemplified by the solar eclipse at 29 March 2006. Using a backward Monte Carlo model we calculated the diffuse radiation in the umbra and simulated the changing colours of the sky. Radiance and irradiance are decreased by 3 to 4 orders of magnitude, depending on wavelength. We found that aerosol has a comparatively small impact on the radiation in the umbra. We also estimated the contribution of the solar corona to the radiation under the umbra and found that it is negligible compared to the diffuse solar radiation in the wavelength region from 310 to 500 nm.

show abstract

Section: Radiance and Irradiance Spectrasupporting

confidence: 86%

Simulation of solar radiation during a total eclipse: a challenge for radiative transfer

2007

View full text Add to dashboard Cite

show abstract

“…The distribution of skylight polarization has been investigated under clear [9][10][11], partly cloudy [12,13], overcast [14,15], foggy [15,16], and smoky [17] sky conditions as well as under tree canopies [18]. The polarization characteristics of the sky were also measured under such extreme conditions as total solar eclipses [19][20][21][22][23][24][25] and at the edge of ice-sea on the high Arctic [26]. Sky-polarization patterns were also investigated during moonless twilight [27] and at full moon [28].…”

Section: Introductionmentioning

confidence: 99%

Polarization transition between sunlit and moonlit skies with possible implications for animal orientation and Viking navigation: anomalous celestial twilight polarization at partial moon

et al. 2014

View full text Add to dashboard Cite

Using full-sky imaging polarimetry, we measured the celestial distribution of polarization during sunset and sunrise at partial (78% and 72%) and full (100%) moon in the red (650 nm), green (550 nm), and blue (450 nm) parts of the spectrum. We investigated the temporal change of the patterns of degree p and angle α of linear polarization of sunlit and moonlit skies at dusk and dawn. We describe here the position change of the neutral points of sky polarization, and present video clips about the celestial polarization transition at moonlit twilight. We found that at partial moon and at a medium latitude (47° 15.481' N) during this transition there is a relatively short (10-20 min) period when (i) the maximum of p of skylight decreases, and (ii) from the celestial α pattern neither the solar-antisolar nor the lunar-antilunar meridian can be unambiguously determined. These meridians can serve as reference directions of animal orientation and Viking navigation based on sky polarization. The possible influence of these atmospheric optical phenomena during the polarization transition between sunlit and moonlit skies on the orientation of polarization-sensitive crepuscular/nocturnal animals and the hypothesized navigation of sunstone-aided Viking seafarers is discussed.

show abstract

“…These polarimeters were oriented in a given direction of view in the Sun's vertical. [2][3][4][5][6][7] It was a great technical achievement when Shaw 8 was able to scan the sky along the solar-antisolar meridian during the total eclipse on 30 June 1973 in Northern Kenya. He observed the approximate cylindrical symmetry of the distribution of the degree of polarization p of the eclipse sky and near the zenith a local minimum of p. Using a numerical model, Können 9 explained quantitatively several polarization characteristics of the eclipse sky.…”

Section: Introductionmentioning

confidence: 99%

Neutral points of skylight polarization observed during the total eclipse on 11 August 1999

2003

View full text Add to dashboard Cite

We report here on the observation of unpolarized (neutral) points in the sky during the total solar eclipse on 11 August 1999. Near the zenith a neutral point was observed at 450 nm at two different points of time during totality. Around this celestial point the distribution of the angle of polarization was heterogeneous: The electric field vectors on the one side were approximately perpendicular to those on the other side. At another moment of totality, near the zenith a local minimum of the degree of linear polarization occurred at 550 nm. Near the antisolar meridian, at a low elevation another two neutral points occurred at 450 nm at a certain moment during totality. Approximately at the position of these neutral points, at another moment of totality a local minimum of the degree of polarization occurred at 550 nm, whereas at 450 nm a neutral point was observed, around which the angle-of-polarization pattern was homogeneous: The electric field vectors were approximately horizontal on both sides of the neutral point.

show abstract

Sky Brightness and Polarization During the 1973 African Eclipse

Cited by 35 publications

References 10 publications

Simulation of solar radiation during a total eclipse: a challenge for radiative transfer

Simulation of solar radiation during a total eclipse: a challenge for radiative transfer

Polarization transition between sunlit and moonlit skies with possible implications for animal orientation and Viking navigation: anomalous celestial twilight polarization at partial moon

Neutral points of skylight polarization observed during the total eclipse on 11 August 1999

Contact Info

Product

Resources

About