Fig. 1

A model showing the non-ideal velocity and the measurement results. a Coronal loops show the measurement of the non-ideal velocity. The letters p and n stand for the conjugate footpoints of a loop and the subscripts 0 and 1 refer to time labels for the start and end time, t₀ and t₁, for one measurement, respectively. The yellow loop represents the initial loop at t₀ and the transparent yellow loop is the hypothetical version at time t₁ under the assumption of ideal MHD. The footpoints are advected to new places by the photospheric plasma flow, as indicated by the red and blue arrows in positive and negative polarities, respectively. The orange loop is the actual coronal loop at time t₁. The distance denoted by the two-headed arrow is the non-ideal distance δn due to magnetic diffusion (reconnection). b The extrapolated magnetic field at 18:10 UT. c The photospheric plasma velocity field overplotted on the vertical magnetogram from HMI (background). The blue and red arrows represent the plasma flow with positive and negative magnetic flux, respectively. d The force-free parameter, α, calculated from the vector magnetogram at 18:10 UT. e The measured non-ideal velocity. Here, we only calculate the non-ideal velocity where both footpoints of the field lines are rooted within the field of view and \(\left| {\bf{B}} \right| > 20\) G in the magnetograms. f The heating flux calculated from the reconnection model with the parameter \({\mathscr L}\) = 160 km