Unexpected enhancement in secondary cosmic ray flux during the total lunar eclipse of December 10, 2011

AbstractTemporal variation of secondary cosmic rays (SCR) flux was measured during the total lunareclipse on December 10, 2011 and the subsequent full moon on January 8, 2012. The measure-ments were done at Department of Physics, University of Mumbai, Mumbai (Geomagnetic lati-tude: 10.6  N), India using NaI (Tl) scintillation detector by keeping energy threshold of 200KeV.The SCR flux showed approximately 8.1 % enhancement during the lunar eclipse as comparedto the average of pre- and post-eclipse periods. Weather parameters (temperature and relative hu-midity) were continuously monitored and their correlations with temporal variation in SCR fluxwere examined. The influences of geomagnetic field, interplanetary parameters and tidal e ect onSCR flux were considered. Qualitative analysis of SCR flux variation indicates that the knownfactors a ecting SCR flux fail to explain observed enhancement during the eclipse. This enhance-ment during lunar eclipse and widely reported decrease during solar eclipses may unravel hithertounnoticed factors modulating SCR flux.Keywords: Secondary Cosmic Ray (SCR), lunar eclipse, local weather parameters, tidal e ect,geomagnetic field e ect, Interplanetary parameters.1. IntroductionOur planet Earth is being constantly bombarded by high energy particles from the Sun andGalactic Cosmic Rays (GCR). Though the Earth’s magnetic field provides a protective shield sus-taining the life, still high energy GCR manage to reach the Earth and contribute to SecondaryCosmic Rays (SCR) flux. SCR flux variations have been extensively studied for Solar Cycles, 27days’ cycle, diurnal variations, Coronal Mass Ejections (CMEs) and solar eclipses [1, 2]. SCRflux is known to vary with factors such as local weather parameters (temperature, pressure and