Magnetic fields in solar plage regions: insights from high-sensitivity spectropolarimetry

TL;DR

This study uses high-sensitivity spectropolarimetry from DKIST to analyze magnetic fields and dynamics in solar plage regions, revealing detailed magnetic structures and velocity patterns in the chromosphere.

Contribution

It provides new insights into the chromospheric magnetic field stratification and dynamics of plage regions using advanced spectropolarimetric data and inversion techniques.

Findings

Chromospheric magnetic fields in plages range from 200-300 G.

Weak correlation between magnetic field strength and cooling rates.

Detection of supersonic downflows and velocity gradients in plage periphery.

Abstract

Plage regions are patches of concentrated magnetic field in the Sun's atmosphere where hot coronal loops are rooted. While previous studies have shed light on the properties of plage magnetic fields in the photosphere, there are still challenges in measuring the overlying chromospheric magnetic fields, which are crucial to understanding the overall heating and dynamics. Here, we utilize high-sensitivity, spectropolarimetric data obtained by the four-meter Daniel K. Inouye Solar Telescope (DKIST) to investigate the dynamic environment and magnetic field stratification of an extended, decaying plage region. The data show strong circular polarization signals in both plage cores and surrounding fibrils. Notably, weak linear polarization signals clearly differentiate between plage patches and the fibril canopy, where they are relatively stronger. Inversions of the Ca II 8542 $\mathring{A}$ spectra show an imprint of the fibrils in the chromospheric magnetic field, with typical field strength values ranging from $\sim$ 200-300 G in fibrils. We confirm the weak correlation between field strength and cooling rates in the lower chromosphere. Additionally, we observe supersonic downflows and strong velocity gradients in the plage periphery, indicating dynamical processes occurring in the chromosphere. These findings contribute to our understanding of the magnetic field and dynamics within plages, emphasizing the need for further research to explore the expansion of magnetic fields with height and the three-dimensional distribution of heating rates in the lower chromosphere.