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

摘要

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 and 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 a signal-to-noise ratio  ≥ 4.5 covers about 26% of the entire area in the least noisy data in our study (with a noise level of 1.7 × 10⁻⁴ 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 × 10⁻³ s⁻¹ arcsec⁻². The LPFs were found to be short lived (in the range of 30 – 300 s), relatively small structures (radii of  ≈ 0.1 – 1.5 arcsec), highly inclined, posing hG fields, and they 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 an intensity contrast always larger than that of the average quiet Sun.