Time domain analysis of solar coronal structures through hough transform techniques

The Hough transform technique is applied to a series of images from the LASCO/C2 coronagraph in order to understand the temporal evolution of radial structures on the solar corona, the so-called "polar plumes". They may corotate with the solar corona and therefore change aspect with time due to projection effects on the plane of the sky. In the images these structures suddenly appear, shift, mix, and fade away on short periods of time. From a long series of images (similar to 100), we determined for each image the polar intensity profile and built up the evolution of such profiles against; time. The result is a Time Intensity Diagram (TID) where intensities are platted with respect to time and position coordinates. Radial structures appear as-peak intensities in each profile and therefore as bright points in the TID. The Hough transform techniques are applied to detect coherent trajectories. This technique has been applied successfully to study coronal plumes on coronal images obtained by different instruments aboard the SOHO satellite.