On-orbit Performance of the Solar Optical Telescope aboard Hinode

On-orbit performance of the Solar Optical Telescope (SOT) aboard Hinode is described with some attentions on its unpredicted aspects. In general, SOT revealed an excellent performance and has been providing outstanding data. Some unexpected features exist, however, in behaviors of the focus position, throughput and structural stability. Most of them are recovered by the daily operation i.e., frequent focus adjustment, careful heater setting and corrections in data analysis. The tunable filter contains air bubbles which degrade the data quality significantly. Schemes for tuning the filter without disturbing the bubbles have been developed and tested, and some useful procedures to obtain Dopplergram and magnetogram are now available. October and March when the orbit of satellite becomes nearly perpendicular to the direction towards the sun provide a favorable condition for continuous runs of the narrow-band filter imager.

Frequent Occurrence of High-speed Local Mass Downflows on the Solar Surface

We report on new spectro-polarimetric measurements with simultaneous filter imaging observation, revealing the frequent appearance of polarization signals indicating high-speed, probably supersonic, downflows that are associated with at least three different configurations of magnetic fields in the solar photosphere. The observations were carried out with the Solar Optical Telescope onboard the {em Hinode} satellite. High speed downflows are excited when a moving magnetic feature is newly formed near the penumbral boundary of sunspots. Also, a new type of downflows is identified at the edge of sunspot umbra that lack accompanying penumbral structures. These may be triggered by the interaction of magnetic fields sweeped by convection with well-concentrated magnetic flux. Another class of high speed downflows are observed in quiet sun and sunspot moat regions. These are closely related to the formation of small concentrated magnetic flux patches. High speed downflows of all types are transient time-dependent mass motions. These findings suggest that the excitation of supersonic mass flows are one of the key observational features of the dynamical evolution occurring in magnetic-field fine structures on the solar surface.