The Present State of the Solar Flare Problem

Abstract

In contrast to flares on other stars or to many analogous phenomena in the Universe, flares on the Sun are accessible to a broad variety of observational methods. Solar flares emit radiation which covers virtually the whole electromagnetic spectrum, from kilometer radio waves to hard gamma rays, and which can be detected by Earth-based, satellite-borne, and interplanetary observing stations. At the same time, the particles accelerated in the flare, the plasma ejected into the interplanetary space, and secondary ionospheric and geomagnetic events related to the flare are detected directly. As a result, during the last two decades solar flare research has become very comprehensive, in particular during the years of coordinated international programs. An intense stream of very diverse observational data on solar flares and secondary events allowed us to obtain new and more detailed information about the solar flare mechanism.