Blue-wing enhancement of the chromospheric Mg ii h and k lines in a solar flare

PASJ: Publications of the Astronomical Society of Japan

Heinzel, Petr¹  Tei, Akiko²  Shibata, Kazunari²  Ichimoto, Kiyoshi²  Asai, Ayumi²  Sakaue, Takahito²  UeNo, Satoru²  Kawate, Tomoko³  Okamoto, Takenori J⁴ 

[1] Astronomical Institute, Czech Academy of Sciences, 25165 Ondřejov, Czech Republic;Astronomical Observatory, Kyoto University, 17 Ohmine-cho Kita Kazan, Yamashina-ku, Kyoto, Kyoto 607-8471, Japan;Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan;National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan

关键词: Sun: activity;    Sun: chromosphere;    Sun: flares;    Sun: transition region;    Sun: UV radiation;   

DOI  :  10.1093/pasj/psy047

学科分类：天文学(综合)

来源: Oxford University Press

【 摘 要 】

We performed coordinated observations of AR 12205, which showed a C-class flare on 2014 November 11, with the Interface Region Imaging Spectrograph (IRIS) and the Domeless Solar Telescope (DST) at Hida Observatory. Using spectral data in the Si iv 1403 Å, C ii 1335 Å, and Mg ii h and k lines from IRIS and the Ca ii K, Ca ii 8542 Å, and Hα lines from DST, we investigated a moving flare kernel during the flare. In the Mg ii h line, the leading edge of the flare kernel showed an intensity enhancement in the blue wing and a smaller intensity of the blue-side peak (h2v) than that of the red-side one (h2r). The blueshift lasted for 9–48 s with a typical speed of 10.1 ±  2.6 km s−1, which was followed by a high intensity and a large redshift with a speed of up to 51 km s−1 detected in the Mg ii h line. The large redshift was a common property for all six lines, but the blueshift prior to it was found only in the Mg ii lines. Cloud modeling of the Mg ii h line suggests that the blue-wing enhancement with such a peak difference could have been caused by a chromospheric-temperature (cool) upflow. We discuss a scenario in which an upflow of cool plasma is lifted up by expanding hot plasma owing to the deep penetration of non-thermal electrons into the chromosphere. Furthermore, we found that the blueshift persisted without any subsequent redshift in the leading edge of the flare kernel during its decaying phase. The cause of such a long-lasting blueshift is also discussed.

【 授权许可】

CC BY