Color Portion of Solar Radiation in the Partial Annular Solar Eclipse, October 3rd, 2005, at Helwan, Egypt

Abstract

Measurements were made of various solar radiation components, global, direct and diffuse and their fractions during the partial annular solar eclipse on October 3rd, 2005 at Helwan, Egypt (Lat. 29.866◦ N and Long. 31.20◦ E), and an analysis has been made. The duration of the solar eclipse was 3 h 17 min, and the maximum magnitude of the eclipse in this region was 0.65. The optical depth of the direct component and the relative humidity decreased, while both the transparency and the air temperature increased towards the maximum eclipse. The general trends of the global components are decreasing optical depth and increasing transparency between the first contact and the last contact. The prevailing color during the eclipse duration was diffused infrared (77 % of the total diffuse radiation level).

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“…For the eclipse of 2005, Hassan et al (2010) [159] found at Helwan that at maximum eclipse, optical depth decreased while transparency improved. The air temperature decreased by an amount of 1.8 • C and a 2% increase in RH was recorded.…”

“…Some of them have been observed from countries of northern Africa and from the Near-East. Measurements of the atmospheric response during the annular solar eclipse of 3 October 2005 have been reported in these regions by [159] in Egypt, and by Anbar (2006) [118] in Saudi Arabia. Also during the total solar eclipse of 29 March 2006, measurements made by Möllman and Vollmer (2006) [160], Uddin et al (2007) [123], Pintér et al (2008), Pleijel (2008) [20] and Stoev et al (2008Stoev et al ( , 2012 [122,161] in Turkey, by Nawar et al (2007) [162] in Egypt, by [119] in Libya and, by Nymphas et al (2009) [163] in Nigeria, were reported.…”

“…Photoelectric observations made by Nawar et al (2007) [162] at the Egyptian site of Salloum revealed that the sky brightness, in the region around the Sun during totality, was brighter than in the zenith with a value of 0.86 mag-arcsec −2 for yellow and of 1.58 mag-arcsec −2 for red. At the Libyan site of Tobruq Hassan and Rahoma (2010) [159] were able to detect an increase of RH from 62% at first contact to 82% at maximum, and a drop in temperature from 19.5 • C to 18.0 • C at the same instants; also, they found that the maximum percent of color in the total direct solar radiation was 57.68% for infrared followed by 15.69% for yellow, 14.88% for red and 11.74% for green. And at the Nigerian site of Ibadan Nymphas et al (2009) [163] reported a drop in temperature of 1.6, 1.0 and 0.8 • C at 1, 6 and 12 m (above ground level), respectively during the eclipse; at the same time, results for wind indicated that there was a reduction in speed before totality at different heights, for example, from 2.02 to 0.48 m-s −1 at 1 m, from 2.39 to 0.75 m-s −1 at 3 m, from 2.67 to 0.93 m-s −1 at 6 m, and from 3.06 to 1.13 m-s −1 ; global solar radiation reached a minimum of about 25.44 W-m −2 at totality and net radiation dropped from 354.27 to −3.56 W-m −2 during totality.…”