Hard X-ray imaging of a solar gradual hard X-ray burst on April 1, 1981 |
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| Authors: | T Takakura K Ohki T Sakurai J L Wang J Y Xuan S C Li R Y Zhao |
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| Institution: | (1) Department of Astronomy, University of Tokyo, Bunkyo-ku, 113 Tokyo, Japan;(2) Tokyo Astronomical Observatory, University of Tokyo, Mitaka, 181 Tokyo, Japan;(3) Peking Astronomical Observatory, Academia Sinica, Peking, China;(4) Yunnan Observatory, Academia Sinica, Kunming, China |
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| Abstract: | An intense solar X-ray burst occurred on April 1, 1981. X-ray images of this gradual hard X-ray burst were observed with the hard X-ray telescope aboard the Hinotori satellite for the initial ten minutes of rise and maximum phases of the burst. The hard X-ray images (13–29 keV) look like a large loop without considerable time variation of an elongated main source during the whole observation period. The main X-ray source seems to lie along a ridge of a long coronal arcade 2 × 104 km above a neutral line, while a tangue-like sub-source may be another large coronal loop although the whole structure of the X-ray source looks like a large semi-circular loop. Both nonthermal and hot thermal (3–4 × 107 K) electrons are contributing to the source image. The ratio of these components changed in a wide range from 2.3 to 0.4 during the observation, while the image was rather steady. It suggests that both heating and accelerations of electrons are occurring simultaneously in a common source. Energetic electrons of 15–30 keV would be collisionally trapped in the coronal magnetic loops with density of the order of 1011 cm–3. |
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