MOTIONS OF ISOLATED G-BAND BRIGHT POINTS IN THE SOLAR PHOTOSPHERE

摘要

Magnetic elements on the quiet Sun are buffeted by convective flows that cause lateral motions on time-scales of minutes. The magnetic elements can be observed as bright points (BPs) in the G band at 4305 A. We present observations of BPs based on a long sequence of G-band images recorded with the Dutch Open Telescope and postprocessed using speckle-masking techniques. From these images we measured the proper motions of isolated BPs and derived the autocorrelation function of their velocity relative to the solar granulation pattern. The accuracy of BP position measurements is estimated to be less than 23 km on the Sun. The rms velocity of BPs (corrected for measurement errors) is about 0.89 km s~(―1), and the correlation time of BP motions is about 60 s. This rms velocity is about 3 times the velocity measured using cork tracking, almost certainly due to the fact that isolated BPs move more rapidly than clusters of BPs. We also searched for evidence of vorticity in the motions of G-band BPs.