Proper motions of solar Type-I sources

Radio tracking of the Sun over 6 hrs around transit was made by the Miyun 460 MHz compound interferometer to determine the two-imensional positions of Type-I sources and their proper motions. The measuring error in relative position was less than 0.1'.

Most of Type-I sources show slow motions at times. The speed ranges from the interferometer threshold of 0.2′/hr to 2′/hr (2.4(+6) cm/s). The largest proper motion found was 5' in 6 hrs, but the usual amplitudes were 1'-2' in 6 hrs. Active regions with moving Type-I sources show more flare activity, i.e. more flares of importance class 1 or greater within a three day period around the day when the source shows motion, while other regions are not so active. The proper motion is sometimes related to photospheric phenomena.

We believe that the proper motion of a Type-I source is a reflection of the changing configuration of the coronal magnetic field above the active region and this variation could be related to flare activity.