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Huw Morgan (Aberystwyth University): Ubiquitous and continuous propagating disturbances in the solar corona

3pm - 4pm, Mon, 23 Apr '18
Location: PS128

Abstract: A new processing method applied to Atmospheric Imaging Assembly/Solar Dynamic Observatory observations reveals continuous propagating faint motions throughout the corona. The amplitudes are small, typically 2\%\ of the background {\color{black} \color{black}intensity}. An hour's data is processed from four AIA channels for a region near disk center, and the motions characterized using an optical flow method. The motions trace the underlying large-scale magnetic field. The motion vector field describes large-scale coherent regions that tend to converge at narrow corridors. Large-scale vortices can also be seen. The hotter channels have larger-scale regions of coherent motion compared to the cooler channels, interpreted as the typical length of magnetic loops at different heights. Regions of low mean and high time variance in velocity are where the dominant motion component is along the line of sight due to a largely vertical magnetic field. The mean apparent magnitude of the optical velocities are a few tens of \kms, with different distributions in different channels. {\color{black} Over time, the velocities vary smoothly between a few \kms\ to 100\kms\ or higher, varying on timescales of minutes. A clear bias of a few \kms\ towards positive $x$-velocities is due to solar rotation and may be used as calibration in future work.} All regions of the low corona thus experience a continuous stream of propagating disturbances at the limit of both spatial resolution and signal level. The method provides a powerful new diagnostic tool for tracing the magnetic field, and to probe motions at sub-pixel scales, with important implications for models of heating and of the magnetic field.

Tags: CFSA Seminar

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