Fan-shaped jets above the light bridge of a sunspot driven by reconnection

摘要

We report on a fan-shaped set of high-speed jets above a strongly magnetized light bridge (LB) of a sunspot observed in the H α line. We study the origin, dynamics, and thermal properties of the jets using high-resolution imaging spectroscopy in H α from the Swedish 1m Solar Telescope and data from the Solar Dynamics Observatory and Hinode. The H α jets have lengths of 7–38 Mm, are impulsively accelerated to a speed of ~ 100 km s ~(-1) close to photospheric footpoints in the LB, and exhibit a constant deceleration consistent with solar effective gravity. They are predominantly launched from one edge of the light bridge, and their footpoints appear bright in the H α wings. Atmospheric Imaging Assembly data indicates elongated brightenings that are nearly co-spatial with the H α jets. We interpret them as jets of transition region temperatures. The magnetic field in the light bridge has a strength of 0.8?2 kG and it is nearly horizontal. All jet properties are consistent with magnetic reconnection as the driver.