Empirical model for the upper limit spectrum for solar cosmic rays at the earth's orbit

Abstract

Based on direct and indirect observation data at the Earth's orbit an attempt is performed to synthesize the complete spectrum of solar cosmic rays (SCR) for the whole range of their energies of order 1 MeV-10 GeV (for the protons). The methodical difficulties of such a synthesis are discussed (observation accuracy, SCR anisotropy, SCR energy density in the non-relativistic region, upper energy limit for registered protons, etc.). Proton spectra and the energy density are determined for the most powerful SCR events of the period 1942–1992. Taking into account the systematic errors and energy dependence of the spectral index, we present an empirical curve of the upper limit SCR spectrum (ULS) near the Earth's orbit. The results demonstrate the possibility of combining the extreme features of relativistic and non-relativistic SCR within the single model of “a worst case” for the solar proton event (SPE). The areas of application of the suggested empirical model would be calculations and predictions of SCR effects on spacecraft design systems and crews, on the ionosphere, ozone layer and other terrestrial envelopes.