The most energetic solar flares: detection of solar neutrons and solar cosmic rays

In this talk, I show a typical example of a solar flare event on April 15, 2001 that clearly suggests the particle acceleration mechanism. Then I propose that solar physics is the easiest way to demonstrate the particle acceleration mechanism. In the flare of April 15, 2001, particles were accelerated beyond 56 GeV. The event is highly consistent with the hypothesis that particles are accelerated by the shock acceleration mechanism. The acceleration site was clearly observed by the Yohkoh X-ray telescope and making it possible to compare the Yohkoh X-ray data with ground-based detector data.