Spectra and anisotropy during GLE # 4 on 19 November 1949 derived using historical records

Abstract

Abstract

A methodological study of solar energetic particles provides the necessary basis to understand the mechanisms of their acceleration and propagation in interplanetary space. According to the current paradigm, following solar eruptive processes, such as solar flares and/or coronal mass ejections, solar ions can be accelerated to high energies. In most cases, the energy of the accelerated solar ions is several tens of MeV/n, yet in some cases, it exceeds 100 MeV/n and occasionally reaches the GeV/n range. In the latter case, the energy is sufficient for solar ions to generate an atmospheric cascade in the Earth’s atmosphere with secondary particles reaching the ground and registered by ground-based detectors. This particular class of events is known as ground-level enhancements (GLEs). At present, 73 GLEs in total have been detected, starting with the Forbush first observations in 1942. The first three events were registered only by ionization chambers; the fourth event was recorded by ionization chambers, muon telescopes, and a non-standard neutron monitor. Using the historical records of ionization chambers, namely their count-rate increases, and a state-of-the-art model, we assessed the spectra of GLE # 4 that occurred on 19 November 1949. We employed a method adapted from neutron monitor data analysis, that is, modelling the ionization chamber responses and other detectors and optimization over the experimental count rate increases. Hence, we assessed the GLE # 4 spectra, hgere presenting preliminary results.