Upgrading the Terminal System on the Fine-structure Heliograph at Gan-Yu Station of Purple Mountain Observatory and Some New Observational Results

Abstract In order to observe the bombardment of the solar chromosphere by high-speed electrons from flares, the fine-structure heliograph at Gan-Yu station of Purple Mountain Observatory has been upgraded to a high-speed CCD instrument that takes H α filtergrams of solar local active regions. A focal reducer is added to the original optical system, and after introducing the polarization interference filter, the H α filtergrams at different wavebands can be obtained by the fast CCD terminal. After repeated tests and improvements during the years 1999–2004, the upgrading is now completed with good result: the spatial resolution reaches 1 arcsec, and the temporal resolution is 30–40 frames per second. In November 2004, a class-M1.1 flare was observed. Comparing the blue-shifted H α (H α –0.5 A) high-speed heliograms with the hard X-ray and microwave burst observations, we find that a pair of bright points moved toward each other during the rising phase of the initial flare. The converging motion was also displayed by the sources of the microwave burst. This phenomenon has never been observed before, and it can be explained as a shearing motion of the footpoints of the magnetic arch along the magnetic neutral line.