JKAS - Journal of the Korean Astronomical Society

The Korean Astronomical Society

JKAS is a bimonthly publication of the Korean Astronomical Society. We aim at promoting the original work of researchers in all branches of astronomy and astrophysics. We cover all categories of work, including observation, theory, methodology, instrumentation, software, and data bases. We welcome proposals for review articles or special issues.

JKAS was launched in 1968 to provide a peer-reviewed scientific journal to the Korean community of astronomers. As there were only a few professional astronomers in Korea back then, JKAS initially published one issue per year, with each issue containing a handful of papers written either in Korean or English. The first-ever JKAS paper was written by Chou & Kitamura and discussed the photometric orbit of the eclipsing binary DI Pegasi. Over time, the Korean astronomy community grew, and so did the number of papers. In 1986, JKAS became English-only, with Korean language papers spun off to the Publications of the Korean Astronomical Society (PKAS). Around 2004/2005, the astronomical societies of Korea, Japan, China, and India discussed a merger of their national astronomy journals, including JKAS, into a unified Asian journal; eventually, this proposal was rejected In the past decade, efforts were made to make JKAS fit for the 21st century. In 2009, JKAS was added to the ISI/Thomson Reuters Science Citation Index Expanded database and received an impact factor, thus at last joining the family of globally recognized quality scientific journals. Nowadays, JKAS receives about 40 to 50 papers per year out of which 20 to 30 are accepted and published.

Journal of the Korean Astronomical Society - Vol. 52 , No. 4

52: 89 - 97, 2019 August

https://doi.org/10.5303/JKAS.2019.52.4.89

MERGING AND FRAGMENTATION IN THE SOLAR ACTIVE REGION 10930 CAUSED BY AN EMERGING MAGNETIC FLUX TUBE WITH ASYMMETRIC FIELD-LINE TWIST DISTRIBUTION ALONG ITS AXIS

Tetsuya Magara

Abstract:

We demonstrate the subsurface origin of the observed evolution of the solar active region 10930 (AR10930) associated with merging and breakup of magnetic polarity regions at the solar surface. We performed a magnetohydrodynamic simulation of an emerging magnetic flux tube whose field-line twist is asymmetrically distributed along its axis, which is a key to merging and fragmentation in this active region. While emerging into the surface, the flux tube is subjected to partial splitting of its weakly twisted portion, forming separate polarity regions at the solar surface. As emergence proceeds, these separate polarity regions start to merge and then break up, while in the corona sigmoidal structures form and a solar eruption occurs. We discuss what physical processes could be involved in the characteristic evolution of an active region magnetic field that leads to the formation of a sunspot surrounded by satellite polarity regions.


Key words: Sun: activity Sun: magnetic fields magnetohydrodynamics methods: numerical

Received February 28, 2019; accepted June 10, 2019