Properties of photospheric bright points (BPs) near an active region have been studied in TiO λ 7058Å images observed by the New Vacuum Solar Telescope of the Yunnan Observatories. We developed a novel recognition method that was used to identify and track 2010 BPs. The observed evolving BPs are classified into isolated (individual) and non-isolated (where multiple BPs are observed to display splitting and merging behaviors) sets. About 35.1% of BPs are non-isolated. For both isolated and non-isolated BPs, the brightness varies from 0.8to1.3 times the average background intensity and follows a Gaussian distribution. The lifetimes of BPs follow a lognormal distribution, with characteristic lifetimes of (267±140)s and (421±255)s, respectively. Their size also follows log-normal distribution, with an average size of about (2.15±0.74)×10 4 km 2 and (3.00±1.31)× 10 4 km 2 for area, and (163±27) km and (191±40) km for diameter, respectively. Our results indicate that regions with strong background magnetic field have higher BP number density and higher BP area coverage than regions with weak background field. Apparently, the brightness/size of BPs does not depend on the background field. Lifetimes in regions with strong background magnetic field are shorter than those in regions with weak background field, on average.

Granules observed in the solar photosphere are believed to be convective and turbulent, but the physical picture of the granular dynamical process remains unclear. Here we performed an investigation of granular dynamical motions of full length scales based on data obtained by the 1 m New Vacuum Solar Telescope and the 1.6 m Goode Solar Telescope. We developed a new granule segmenting method, which can detect both small faint and large bright granules. A large number of granules were detected, and two critical sizes, 265 and 1420 km, were found to separate the granules into three length ranges. The granules with sizes above 1420 km follow Gaussian distribution, and demonstrate flat in flatness function, which shows that they are non-intermittent and thus are dominated by convective motions. Small granules with sizes between 265 and 1420 km are fitted by a combination of power-law function and Gauss function, and exhibit nonlinearity in flatness function, which reveals that they are in the mixing motions of convection and turbulence. Mini granules with sizes below 265 km follow the power-law distribution and demonstrate linearity in flatness function, indicating that they are intermittent and strongly turbulent. These results suggest that a cascade process occurs: large granules break down due to convective instability, which transports energy into small ones; then turbulence is induced and grows, which competes with convection and further causes the small granules to continuously split. Eventually, the motions in even smaller scales enter in a turbulence-dominated regime.

Investigation of the properties of photospheric magnetic fields could shed light on the generation mechanism of small-scale magnetic fields in quiet regions. In this work, we studied the transversal magnetic fields by analyzing the linear polarization (LP) features with Sunrise IMaX data. We calculated the area coverage of LP features, and found that they are 16.1%, 8.6%, and 3% for signals above 3, 3.5, and 4.5 times of noise level, respectively. Those LP features extracted above 4.5 times of noise level are further analyzed. A proper value of 1.5 × 1015 Mx for the net magnetic flux contained in LP features is selected to divide the LP features into two types (I and II). Among all detected snapshot LP features, 86% of them are in type I and the rest are in type II. The length scales of LP features in these two types follow Gauss and power-law distributions, separately. For the topology of magnetic fields in type I, the magnetic flux patches might be footpoints of flux loops that root inside transversal magnetic fields with one unipolar thick leg or one thick leg together with one thin leg in opposite polarity. For those in type II, about 50% of them contain bipolar magnetic flux patches, but the rest appear without magnetic flux patches.