Opposite polarity field with convective downflow and its relation to magnetic spines in a sunspot penumbra

TL;DR

This study uses high-resolution spectropolarimetric data to identify opposite polarity magnetic lanes with convective downflows in a sunspot penumbra, supporting the convective gap model and recent simulations.

Contribution

It provides observational evidence of opposite polarity lanes with downflows in a sunspot penumbra, aligning with the convective gap model and 3D MHD simulations.

Findings

Opposite polarity lanes are located at intra-spine boundaries.

Downflows of about 1 km/s are associated with these lanes.

Strong convective flows with RMS velocities of 1.2 km/s are present throughout the penumbra.

Abstract

We discuss NICOLE inversions of Fe I 630.15 nm and 630.25 nm Stokes spectra from a sunspot penumbra recorded with the CRISP imaging spectropolarimeter on the Swedish 1-m Solar Telescope at a spatial resolution close to 0.15". We report on narrow radially extended lanes of opposite polarity field, located at the boundaries between areas of relatively horizontal magnetic field (the intra-spines) and much more vertical field (the spines). These lanes harbor convective downflows of about 1 km/s. The locations of these downflows close to the spines agree with predictions from the convective gap model (the "gappy penumbra") proposed six years ago, and more recent 3D MHD simulations. We also confirm the existence of strong convective flows throughout the entire penumbra, showing the expected correlation between temperature and vertical velocity, and having vertical RMS velocities of about 1.2 km/s.