We performed an analysis of high-energy particle emission from the Sun in two extreme solar
particle events observed even with ground-based neutron monitors (NMs). We model particle
transport and interactions from near-Sun source through the solar wind and the Earth’s magnetosphere
and atmosphere in order to make a deep analysis of the events. The time profile of
the proton source at the Sun is deduced and compared with observed electromagnetic emissions.
Several complementary to each other data sets are studied jointly with the broadband dynamic
radio spectra, EUV images as well as other data available for both events. We find a common
scenario for both eruptions, including the flare’s dual impulsive phase, the coronal mass ejection
(CME)-launch-associated burst and the late low-frequency type III radio bursts at the time of the
relativistic proton injection into the interplanetary medium. The analysis supports the idea that
the two considered events start with emission of relativistic protons previously accelerated during
the flare and CME launch, then trapped in large-scale magnetic loops and later released by the
expanding CME.