Extraction of Solar Coronal Magnetic Loops with the Directional 2D Morlet Wavelet Transform

Abstract

We present an automated extraction method based on the continuous wavelet transform (CWT) for analyzing solar magnetic loops. The aim of the work is to extract, from the images taken from solar EUV telescopes, the traces of bright loops presumably shaped by the magnetic field of the solar corona. The technique is that of wavelet analysis, using the two-dimensional Morlet wavelet, because of its efficiency in detecting oriented features, which allows us to follow closely the curvature of the loops. Next, we segment the wavelet modulus image and we threshold it, both globally and locally ( i.e ., adaptively), in order to eliminate the remaining noise. Altogether, our method performs well, it is robust and fast, and could be used as a standard tool for analyzing large data sets expected from missions like SDO.