3D Reconstruction of Coronal Loops by the Principal Component Analysis

Knowing the three dimensional structure of plasma filaments in the uppermost 1 part of the solar atmosphere, known as coronal loops, and especially their length, is an 2 important parameter in the wave-based diagnostics of this part of the Sun. The combination 3 of observations of the Sun from different points of observations in space, thanks to the 4 most recent missions including SDO and STEREO, allows us to infer information on the 5 geometrical shape of coronal loops in the 3D space. Here, we propose a new method 6 to reconstruct the loop shape starting from stereoscopically determined 3D points, which 7 sample the loop length, by the Principal Component Analysis. This method is shown to 8 retrieve in an easy way the main parameters that define loop, e.g. the minor and major axes, 9 the loop plane, the azimuthal and inclination angles, for the special case of a coplanar loop. 10