Regular Pulses from the Sun and a Possible Clue to the Origin of Solar Cosmic Rays

Solar radio and X-ray fluxes sometimes show almost-regular pulsations, and it is now trendy to associate these with the study of "coronal seismology." These are often termed QPP, for "quasi-periodic pulsations," and of course the time constants contain information about the medium and its plasma physics. There are QPP known also in other branches of astrophysics, but probably with very different explanations. Meter-wave radio observations often see very clean wave trains, and the QPP reported in this paper have a much higher Q value (ie, are less "quasi") than the rapidly-damped coronal oscillations discovered in the EIT observations. The cartoon and the paper have a modern ring to them, even if the cartoon technology itself is pretty primitive. Here we see a global wave rushing through a weakly-coupled coronal loop, setting it into motion.