Extreme solar events: An update

Before a dozen years ago, we believed that the Sun is a mildly active star unable to produce disastrous events. However, as discovered in 2012, extreme events can be produced by the Sun rarely on the millennial timescales. These events include extreme solar particle events with enormous fluxes of solar energetic particles as known from cosmogenic-isotope proxies recorded in independently dateable natural archives like tree rings and polar ice cores; and super-flares as known from an analysis of thousands of sun-like stars observed recently by the space-borne telescope Kepler . While both types of events imply that the Sun can rarely produce eruptive events several orders of magnitude stronger than those we observed during the last decades, the statistics of the two types of events mismatch quantitatively. Here, we briefly summarize the start-of-the-art knowledge of the extreme events updating more detailed recent reviews and listing the open questions still remaining to be answered.