@article{1e0fc700ba62410a9ef799c2cfdcc31c,
title = "Observation of a Large-scale Quasi-circular Secondary Ribbon Associated with Successive Flares and a Halo CME",
abstract = "Solar flare ribbons provide an important clue to the magnetic reconnection process and associated magnetic field topology in the solar corona. We detected a large-scale secondary flare ribbon of a circular shape that developed in association with two successive M-class flares and one coronal mass ejection. The ribbon revealed interesting properties such as (1) a quasi-circular shape and enclosing the central active region (AR); (2) the size as large as 500″ by 650″; (3) successive brightenings in the clockwise direction at a speed of 160 km s-1 starting from the nearest position to the flaring sunspots; (4) radial contraction and expansion in the northern and the southern part, respectively, at speeds of ≤10 km s-1. Using multi-wavelength data from Solar Dynamics Observatory, RHESSI, XRT, and Nobeyama, along with magnetic field extrapolations, we found that: (1) the secondary ribbon location is consistent with those of the field line footpoints of a fan-shaped magnetic structure that connects the flaring region and the ambient decaying field; (2) the second M2.6 flare occurred when the expanding coronal loops driven by the first M2.0 flare encountered the background decayed field; (3) immediately after the second flare, the secondary ribbon developed along with dimming regions. Based on our findings, we suggest that interaction between the expanding sigmoid field and the overlying fan-shaped field triggered the secondary reconnection that resulted in the field opening and formation of the quasi-circular secondary ribbon. We thus conclude that interaction between the AR and the ambient large-scale fields should be taken into account to fully understand the entire eruption process.",
keywords = "Sun: activity, Sun: chromosphere, Sun: corona, Sun: flares, Sun: magnetic fields",
author = "Lim, {Eun Kyung} and Vasyl Yurchyshyn and Pankaj Kumar and Kyuhyoun Cho and Chaowei Jiang and Sujin Kim and Heesu Yang and Jongchul Chae and Cho, {Kyung Suk} and Jeongwoo Lee",
note = "Funding Information: E.-K.L. and other KASI members are supported by the KASI Planetary system research for space exploration grant. V.Y. acknowledges support from AFOSR FA9550-15-1-0322 and NSF AST-16114457 grants. P.K. is supported by an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by Universities Space Research Association through a contract with NASA. Funding Information: E.-K.L. and other KASI members are supported by the KASI “Planetary system research for space exploration” grant. V.Y. acknowledges support from AFOSR FA9550-15-1-0322 and NSF AST-16114457 grants. P.K. is supported by an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by Universities Space Research Association through a contract with NASA. The work of the SNU team was supported by the Korea Astronomy and Space Science Institute under the R&D program, Development of a Solar Coronagraph on International Space Station (Project No. 2017-1-851-00), supervised by the Ministry of Science, ICT, and Future Planning. The SDO data were (partly) provided by the Korea Data Center (KDC) for SDO in cooperation with NASA, which is supported by the “Development of Korea Space Weather Research Center” project of the Korea Astronomy and Space Science Institute (KASI). RHESSI is a NASA Small Explorer. Hinode is a Japanese mission developed and launched by ISAS/JAXA, with NAOJ as domestic partner and NASA and STFC (UK) as international partners. SOHO is a project of international cooperation between the ESA and NASA. The Nobeyama Radioheliograph and Polarimeters are operated by the International Consortium for the Continued Operation of Nobeyama. This work was partly carried out on the Solar Data Analysis System (SDAS) operated by the Astronomy Data Center in cooperation with the Solar Observatory of the National Astronomical Observatory of Japan. Publisher Copyright: {\textcopyright} 2017. The American Astronomical Society. All rights reserved.",
year = "2017",
month = dec,
day = "1",
doi = "10.3847/1538-4357/aa93f7",
language = "English (US)",
volume = "850",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "2",
}