Repeated Sunspot Light Bridge Jets Associated with Slipping Base Brightenings

TL;DR

This study investigates recurrent light bridge jets in sunspots, revealing that slipping magnetic reconnection driven by quasi-periodic horizontal motions likely powers these small-scale eruptive phenomena.

Contribution

It provides direct observational evidence of slipping reconnection along sunspot light bridges and links LB jets to coronal jet mechanisms.

Findings

LB jets exhibit slipping motions at their bases with velocities of 0.6-1.5 km/s.

Quasi-periodic horizontal motions of 1.3-6.5 km/s are correlated with jet base slipping.

Spectral signatures indicate magnetic reconnection at the jet bases.

Abstract

Light bridge (LB) jets offer a unique window into small-scale eruptive phenomena within sunspots, the Sun's strongest magnetic environments; however, their generation mechanism remains a subject of debate. Using high-resolution observations from the New Vacuum Solar Telescope (NVST), we investigated six recurrent light bridge jets and the slipping motions of their jet base points (JBPs). Analogous to coronal jets, our observations show that these LB jets are characterized by a preceding JBP followed by a collimated jet spire. The JBP of each repeated jet along the LB displays apparent slipping motion at velocities of 0.6-1.5 km/s, which is temporally correlated with quasi-periodic enhanced photospheric horizontal motion of 1.3-6.5 km/s. Following the slipping JBPs, the resulting jet spires' fronts display similar slipping behaviors within the upper solar atmosphere. The Chinese Ha Solar Explorer (CHASE) reveals Ellerman-bomb-like spectral signatures at the JBPs, confirming that magnetic reconnection is operating at the jet base. Based on these results, we propose that repeated 3D reconnection occurring between the horizontal LB field and the ambient vertical umbral field may drive these LB jets. This process appears to be driven and/or modulated by quasi-periodic horizontal motion fueled by convective upflows and the transport of magnetic flux along the light bridge. This work suggests that some LB jets share a common reconnection-driven mechanism with coronal jets and provides direct evidence of slipping reconnection occurring along the sunspot light bridge.