Characterizing motion types of G-band bright points in the quiet Sun**Supported by the National Natural Science Foundation of China.

Abstract

We study the motion of G-band bright points (GBPs) in the quiet Sun to obtain the characteristics of different motion types. A high resolution image sequence taken with the Hinode/Solar Optical Telescope (SOT) is used, and GBPs are automatically tracked by segmenting 3D evolutional structures in a space-time cube. After putting the GBPs that do not move during their lifetimes aside, the non-stationary GBPs are categorized into three types based on an index of their motion type. Most GBPs that move in straight or nearly straight lines are categorized as a straight motion type, a few moving in rotary paths into rotary motion, and the others fall into a motion type we called erratic. The mean horizontal velocities are 2.18±0.08 km s−1, 1.63±0.09 km s−1 and 1.33±0.07 km s−1 for straight, erratic and rotary motion types, respectively. We find that a GBP drifts at a higher and constant velocity during its whole life if it moves in a straight line. However, it has a lower and variational velocity if it moves on a rotary path. The diffusive process is ballistic-, super- and sub-diffusion for straight, erratic and rotary motion types, respectively. The corresponding diffusion index (γ) and coefficients (K) are 2.13±0.09 and 850±37 km2 s−1, 1.82±0.07 and 331±24 km2 s−1, and 0.73±0.19 and 13±9 km2 s−1. In terms of direction of motion, it is homogeneous and isotropic, and usually persists between neighboring frames, no matter what motion type a GBP is classified as.