Application of the global neutron monitor network for assessment of spectra and anisotropy and the related terrestrial effects of strong SEPs

Abstract

Studies of the characteristic of strong solar energetic particles (SEPs), that is events that can be registered by ground-based instruments such as neutron monitors, allow one to understand their acceleration and propagation in interplanetary space and gives the necessary basis to quantify the related cosmic-ray-induced terrestrial effects. After solar eruptive processes, such as solar flares and/or coronal mass ejections, solar ions are accelerated to the high-energy range. In most cases, the energy of the accelerated solar ions reaches several tens of MeV/n, yet occasionally it exceeds 100 MeV/n or even reaches the GeV/n range. In the latter case, the energy of SEPs is enough, so that they induce an atmospheric particle shower, whose secondary particles reach the ground, eventually registered by ground-based detectors, specifically neutron monitors. This particular class of events is known as ground-level enhancements (GLEs). Here we present a full-chain scheme for assessment of spectra and anisotropy and the related terrestrial effects of GLE causing SEPs. We discuss the application of a method for analysis of GLEs using neutron monitor data and the employment of the derived spectra as a basis to quantify cosmic-ray-induced terrestrial effects during GLEs, specifically atmospheric ionization and exposure to secondary radiation (radiation dose) at cruising aviation altitudes. We present an example study of two GLEs, namely their SEP energy/rigidity spectra derived using records from the global NM network and models for quantification of the atmospheric ionization and exposure to radiation at flight altitudes (ambient dose) during the considered events.