Arrival of the first relativistic solar protons and conditions in the solar corona

When solar cosmic rays (SCRs) can be observed with ground-based equipment (ground-level enhancements, GLEs), events are often characterized by a rapid increase in the relativistic proton intensity during the initial phase, which makes it possible to estimate the time of particle escape from the solar corona. This phase attracts attention of researchers owing to its closeness in time to the instant of particle acceleration. It is known that the observed SCR characteristics bear traces of many physical processes, including different acceleration mechanisms the relative role of which is still unclear. Flare processes and acceleration by a shock, related to coronal mass ejection (CME), are the main pretenders to the role of SCR accelerator. Several powerful solar proton events during cycle 23 are considered in the work, and the release time of the first particles from the corona and the dynamics of CMEs have been estimated. The time series of the X-ray and radio bursts, close in time to particle escape, are analyzed. The conclusion have been drawn that the first relativistic particles were most probably accelerated during flare processes.