  In this note, we consider radio characteristics of three proton flares that
caused discrete enhancements of solar energetic particles (SEPs) near Earth.
The analysis confirmed that the flux density and frequency spectrum of
microwave bursts, although the latter are generated by electrons propagating to
the photosphere, reflect the number and energy spectrum of accelerated
particles, including the 10-100 MeV protons coming to Earth.

Solar and Stellar Astrophysics