Hisashi Hayakawa

The first four ground-level enhancements in the 1940s: investigation, digitization and analysis of forgotten data

Intense solar eruptions occasionally accelerate solar energetic particles (SEPs) and trigger ground-level enhancements (GLEs). Among the 77 known GLEs, the first four #1- 4, in the 1940s, took place before the advent of the standard neutron monitors (NMs) and were missing from th...