Linear Polarization Features in the Quiet-Sun Photosphere: Structure and Dynamics

TL;DR

This study characterizes linear polarization features in the quiet Sun's photosphere using high-resolution Sunrise/IMaX data, revealing their size, dynamics, and physical properties, and how these depend on noise and resolution levels.

Contribution

It provides a detailed analysis of LPFs' structure, dynamics, and physical properties in the quiet Sun, highlighting their dependence on observational noise and resolution, which was not comprehensively studied before.

Findings

LPFs cover about 10% of the area at any time.

LPFs are short-lived, with lifetimes of 30-300 seconds.

LPFs move with an average speed of 1.2 km/s.

Abstract

We present detailed characteristics of linear polarization features (LPFs) in the quiet-Sun photosphere from high resolution observations obtained with Sunrise/IMaX. We explore differently treated data with various noise levels in linear polarization signals, from which structure and dynamics of the LPFs are studied. Physical properties of the detected LPFs are also obtained from the results of Stokes inversions. The number of LPFs, as well as their sizes and polarization signals, are found to be strongly dependent on the noise level, and on the spatial resolution. While the linear polarization with signal-to-noise ratio $\geq4.5$ covers about 26% of the entire area in the least noisy data in our study (with a noise level of $1.7\times10^{-4}$ in the unit of Stokes $I$ continuum), the detected (spatially resolved) LPFs cover about 10% of the area at any given time, with an occurrence rate on the order of $8\times10^{-3}$ s$^{-1}$ arcsec$^{-2}$. The LPFs were found to be short lived (in the range of $30-300$ s), relatively small structures (radii of $\approx0.1-1.5$ arcsec), highly inclined, posing hG fields, and move with an average horizontal speed of 1.2 km s$^{-1}$. The LPFs were observed (almost) equally on both upflow and downflow regions, with intensity contrast always larger than that of the the average quiet-Sun.