We study the motions 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 don ’ t move during their lifetimes aside , the non-stationary GBPs are categorized into three types based on an index of motion type .
Most GBPs that move in straight or nearly straight lines are categorized into a straight motion type , a few moving in rotary paths into a rotary motion , and the others fall into a motion type we called erratic .
The mean horizontal velocity is 2.18 \pm 0.08 km s ^ { -1 } , 1.63 \pm 0.09 km s ^ { -1 } and 1.33 \pm 0.07 km s ^ { -1 } for straight , erratic and rotary motion type , 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 in a rotary path .
The diffusive process is ballistic- , super- and sub-diffusion for straight , erratic and rotary motion type , respectively .
The corresponding diffusion index ( \gamma ) and coefficients ( K ) are 2.13 \pm 0.09 and 850 \pm 37 km ^ { 2 } s ^ { -1 } , 1.82 \pm 0.07 and 331 \pm 24 km ^ { 2 } s ^ { -1 } , 0.73 \pm 0.19 and 13 \pm 9 km ^ { 2 } s ^ { -1 } .
In terms of direction of motion , it is homogeneous and isotropical , and usually persists between neighbouring frames , no matter what motion type a GBP belongs to .