Interactions between Fast Downflows and Fan-shaped Jets above a Penumbral Light Bridge using the Goode Solar Telescope

We present the analysis of high-resolution H α observations of fan-shaped jets above a penumbral light bridge (LB) subject to external disturbance through fast downflows in active region (AR) 12683 using data from the Goode Solar Telescope and the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. We observe jets with an occurrence rate of 5–6 minutes reach heights of 7–14 Mm above the LB with ascent speeds of 70 km s −1 and nearly parabolic trajectories. Associated bright fronts are seen as evidence of shock wave heating. We report the discovery of linear dark condensations of 0.45 Mm thickness that propagate ahead of the jet and shock, which we suggest is matter being compressed in front of the shock. Fast downflows of 40–80 km s −1 reach the south end of the LB with the same periodicity as the jets. The jets and associated small-scale linear structures exhibit horizontal motion, differential with height, along the LB axis at speeds of 35–55 km s −1 away from the interaction site. This speed is consistent with a magnetic field of 40–100 G. We propose that the fast downflows trigger oscillatory magnetic reconnection at the footpoint of the LB, which in turn drive the jets and the horizontal dynamics along the LB. We suggest that the linear fine-structure is the result of perpendicular compressions and rarefactions of reconnected field lines flowing out of the oscillatory reconnection site at Alfvénic speeds.