A study of the gamma-ray flux during the total solar eclipse of 1 August 2008 at Novosibirsk, Russia

Abstract

In the past, there have been reports of the observation of decrease in the flux of secondary cosmic gamma-rays during a total solar eclipse. We have measured the flux of secondary cosmic gamma-rays during the total solar eclipse that occurred at Novosibirsk in Russia, on 1 August 2008. Highly sensitive measurements were carried out by using a detector system with built-in redundancy. The system consisted of two independent, large volume Nal(Tl) scintillator detectors for sensitive and reliable measurements. The data display significant variability in the flux of secondary gamma-rays in the energy range 50-4600 keV. just prior to the total solar eclipse a change similar to 9% in the flux was observed, followed by a small but steady decrease similar to 4% during the eclipse. The temporal variation in the observed flux of gamma-rays were found to be nearly identical for the two detectors. The energy dependence of the variation was further studied by binning the yield in three energy ranges, namely, 100-200, 200-400 and 400-4600 keV. The nearly identical time variation observed in the two independent measurements provides confidence that the measured variation is real and not an artifact of the instrumentation. Systematic observations during the future eclipses are required to study this fascinating phenomenon which is not yet understood.