Solar Energetic Particles and Intensity of Metric Type II Radio Bursts

Abstract

We perform a statistical analysis of 112 proton events from 24 November 2000 to 20 December 2014, accompanied by an increase in the intensity of solar energetic particles (SEPs) with energy $E_{p} > 1$–850 MeV using GOES data. All events were accompanied by metric type II radio bursts in the frequency range of 25–180 MHz observed with the Radio Solar Telescope Network. A correlation in the peak proton integral intensity $I_{p}$ with the intensity of type II radio bursts $I_{i}$ and the frequency drift rate $V$ is shown. Taking into account the helio-longitudinal weakening, i.e. the dependence of SEP intensity on the heliographic longitude of the flare, we find that the correlation coefficients between $I_{p}$ and $I_{i}$, as well as between $I_{p}$ and $V$ for protons with $E_{p} > 30$ MeV are 0.79 and 0.71, respectively. This suggests that non-thermal electrons, which drive type II radio bursts, and energetic protons are generated at the front of the same shock wave. The correlation coefficients mentioned above decrease for $E_{p} \gtrsim100$ MeV. Therefore, the contribution of high energetic protons to the integral intensity $I_{p}$ is rather determined by accelerated processes in the flare energy release region. The weak dependence of SEP intensity on the helio-longitudinal weakening is discussed.