Measurements with STEREO/COR1 data of drag forces acting on small-scale blobs falling in the intermediate corona

In this work we study the kinematics of three small-scale (0.01 R⊙) blobs of chromospheric plasma falling back to the Sun after the huge eruptive event of June 7, 2011. From a study of 3D trajectories of blobs made with the Solar TErrestrial RElations Observatory (STEREO) data, we demonstrate the existence of a significant drag force acting on the blobs and calculate two drag coefficients, in the radial and tangential directions. The resulting drag coefficients CD are between 0 and 5, comparable in the two directions, ...