Influence of forbush effect on atmospheric ionization due to solar energtic particles

Abstract

<div lang="en" class="abs"><p class="abs_header">Abstract</p><p>High-energy precipitating particles of cosmic origin viz. cosmic ray (CR) protons of heavier nuclei of galactic and/or solar origin induce complicated nuclear-electromagnetic-lepton cascades in the Earth’s atmosphere, eventually leading to an ionization of the ambient air. The induced by CRs ionization is related to possible effect of precipitating particles on physico-chemical processes in the atmosphere. These effects can be considerably enhanced during solar proton events. While the contribution of galactic CRs to ion production in the atmosphere is slightly variable throughout a solar cycle, relativistic solar particles could produce a significant excess of electron-ion pair production, particularly over polar caps. This effect is strong on short time scales. On the other hand, depressions of the galactic CR flux, that is, Forbush decreases, can significantly impact on induced ionization. The sequence of three ground level enhancements (GLEs) 65, 66 and 67 in October-November 2003, specifically GLE 66 occurred during a giant Forbush decrease, provides unique opportunity to study impact ionization on enhanced manner and extended time scale, explicitly considering the reduced galactic CR flux. Using Monte Carlo simulations and appropriate solar proton spectra we computed the ion production rate and the corresponding ionization effect in the Earth atmosphere during GLE 66 which occurred on 29 October 2003.</p></div>