''EIT waves'' in Coronal Loops During Non-flare Stage

D. Prosovetsky

Institute of Solar Terrestrial Physics, Irkutsk, Russia

The “EIT waves” term is usually used for the phenomena associated with flare events and subsequent CME. Similar EIT waves are observed in coronal lines (more often in Fe XII 195 line) and a microwave emission (NoRH) as the bright front moving with velocity of 200-400 km/sec on a solar disk and, in some cases, partly above the solar limb. However similar events are not the single wave phenomena which can be found on EIT data. At investigation of large active areas on 2005-2006 the new type of wave perturbations on SOHO/EIT CME watch observation has been found in systems of coronal loops. Waves were observed as the periodic bright and dark fronts moving across vector of a magnetic field in a radial direction to corona. Explored areas were in non-flare phase of their evolution. Velocities of the wave propagation were 8-20 km/sec. Oscillations were observed in active areas on solar disk and loop structures outside solar limb. The wave expansion did not result in changes of topology of a magnetic field and the loops systems in UV radiation. Combined studying of EIT and other observation data has shown source is located at chromospheric level. In the report the nature and probable sources of new type of EIT waves is discussed.