Chromospheric recurrent jets in a sunspot group and their inter-granular origin

TL;DR

This study uses high-resolution solar observations to analyze recurrent chromospheric jets in a sunspot group, revealing their magnetic and dynamic properties and suggesting a convection-driven magnetic reconnection origin.

Contribution

It provides detailed measurements of jet velocities, Doppler shifts, and magnetic field interactions, highlighting the role of inter-granular magnetic reconnection in jet formation.

Findings

Jets reach velocities up to 42 km/s.

Magnetic cancellations occur near jet footpoints.

Horizontal magnetic fields of ~1000 Gauss are impulsively generated.

Abstract

We report on high resolution observations of recurrent fan-like jets by the Goode Solar telescope (GST) in multi-wavelengths inside a sunspot group. The dynamics behaviour of the jets is derived from the Ha line profiles. Quantitative values for one well-identified event have been obtained showing a maximum projected velocity of 42 km s^-1 and a Doppler shift of the order of 20 km s^-1. The footpoints/roots of the jets have a lifted center on the Ha line profile compared to the quiet sun suggesting a long lasting heating at these locations. The magnetic field between the small sunspots in the group shows a very high resolution pattern with parasitic polarities along the inter-granular lanes accompanied by high velocity converging flows (4 km s^-1) in the photosphere. Magnetic cancellations between the opposite polarities are observed in the vicinity of the footpoints of the jets. Along the inter-granular lanes horizontal magnetic field around 1000 Gauss is generated impulsively. Overall, all the kinetic features at the different layers through photosphere and chromosphere favor a convection-driven reconnection scenario for the recurrent fan-like jets, and evidence a site of reconnection between the photosphere and chromosphere corresponding to the inter-granular lanes.