Abstract
Recent observations of solar flares with SOHO/MDI led to discovery of new powerful helioseismic events ("sunquakes"), caused by the impact of high-energy particles. These observations provide important information about the physics of the interaction between high-energy particles and plasma, hydrodynamics of the energy release, and interaction of MHD waves with sunspots, as well as opportunities for developing new helioseismic diagnostics of flaring active regions. The MDI observations revealed new unexpected features of these events, such as a strong anisotropy of the wave amplitude, extended and multiple sources correlated with hard X-ray and white-light emission. It is intriguing that these events so far have been observed only during the declining phase of the solar cycle.