Coronal loop oscillations and flare shock waves

A statistical analysis of coronal loop oscillations observed by TRACE shows that 12 of 28 cases were associated with metric type II bursts. The timing is consistent with the idea that the loop oscillations in many cases result from the passage of a large-scale wave disturbance originating in a flare in the nearby active region. The GOES classifications for these flares range from C4.2 to X20. Typically the oscillating structures are not disrupted, implying that the disturbance has passed through the medium and it has returned to an equilibrium near that prior to the event. This is consistent with the Uchida interpretation of the disturbance as a weak fast-mode blast wave (i.e., a simple wave at low Alfvénic Mach number) propagating in the ambient corona. We note that all 12 of the associated events were also associated with CMEs, and conclude that the CME eruptions in these cases corresponded to only partial openings of the active-region magnetic fields. Subject headings: shock waves — Sun: corona — Sun: flares — Sun: coronal mass ejections (CMEs)