Global coronal waves are observed in the quiet Sun, expanding away from a source region, which is often an active region. Coronal waves have a canonical velocity of 250 km/s, but this can vary greatly from event to event, with velocities ranging from 25 ・438 km/s. They are closely associated with CMEs (there is no such association with flares, so that coronal waves are observed to occur independent of the occurrence of a substantial flare).
The physical mechanism(s) generating the bright fronts remain to be firmly established. Observations of coronal wave fronts (and their associated coronal dimmings that occur behind the bright front) are required to progress our understanding. Multi-temperature observations of a coronal wave bright front from Hinode/XRT, spectral diagnostics from EIS and relation of the bright front to the magnetic field using SOT data, can potentially place significant constraints on the physical mechanisms currently under consideration. |
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