Properties of Streamer Wave Events Observed during the STEREO Era

Abstract:

Transverse waves can sometimes be observed in solar coronal streamers, usually after the passage of a coronal mass ejection (CME). The CME-driven shock displaces the streamer sideways, and a decaying oscillation of the streamer stalk is observed after the CME passage. We present the results of an observational survey of streamer wave events seen from multiple vantage points. We use the data taken by the COR2 instrument on both STEREO A and B, together with the SOHO/LASCO coronagraphs. The properties of streamer waves are studied by comparing the different events and performing a statistical analysis. Common observational features provide an insight on the physical nature of streamer waves. There is no relation between the speed of the CME and the phase speed of the associated streamer wave. This indicates that the streamer wave speed is determined by the streamer's own physical properties and not by the CME properties. This means that streamer waves can be used for coronal seismology. Comparing the measured phase speeds with the speeds calculated from the measured periods and wavelengths, we determine that the speed of the post-shock solar wind outflow in our streamers is around 300 km/s.