The Hunt for the Missing Modes: Revealing the True Nature of the Solar Wind

Abstract

Abstract : This effort produced a novel image-processing algorithm which has allowed successful identification and accurate track of solar plumes in Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) data and, moreover, enabled the first direct measurements of transverse waves in solar polar plumes. This image-processing technique has allowed direct measurement of the transverse displacements, periods and velocity-amplitudes of 596 distinct oscillations in the 171 channel (over a 4 hour period) which displayed a non-uniformly distributed range of parameters. Furthermore, the measurements allow us to take into account the whole of observed non-uniform parameter distribution, permitting the calculation of a more accurate time-averaged energy flux than previously reported. Crucially, this allowed the calculation of an energy flux of 9-24 W m 2, which is 4-10 times below the energy requirement for solar wind acceleration. Hence, the results indicate that transverse magnetohydrodynamic waves as resolved by SDO/AIA cannot be the dominant energy source for fast solar wind acceleration in the open-field corona. The development of this robust, versatile wave-tracking image-processing algorithm can also be applied to a whole range of different solar structures (and in principle to other data sets that display oscillation behaviour). For example, we took advantage of the recent High-resolution Coronal Imager (Hi- C) data and applied the image-processing algorithm to measure the fine-scale structure in transition region moss which led to the first direct observation of transverse wave behaviour of moss in an active region.