Physics Dept Seminar

September 26th, Wednesday (*SPECIAL DAY*)

Observations and Modeling of Flare-productive Active Regions on the Sun

Dr. Shin Toriumi

National Astronomical Observatory of Japan

(Solar Physics - MHD Modeling, Host: Wang)

*SPECIAL TIME: 3:45pm-4:45pm with 3:30pm teatime

*SPECIAL ROOM: FMH 408

Strong solar flares and coronal mass ejections are known to occur in complex active regions (ARs). What kind of AR structures are important for producing these events, and how can we model them? This talk aims at answering to these questions. First, we introduce the statistical analysis on various flare-productive ARs, in which we investigate all >M5.0-class events within 45 deg from disk center for six years from May 2010. We classify them into four categories, namely, (1) Spot-Spot, a complex AR with AR-sized polarity inversion lines (PILs), (2) Spot-Satellite, in which a newly-emerging flux appears adjacent to the pre-existing spot, (3) Quadrupole, where two emerging fields collide against each other, and (4) Inter-AR, the flares occurring between two apparently separated ARs. We find that the characteristics of the flare eruptions strongly depend on the groups; for example, the flare duration of the majority group (1) is four times longer than that of another majority group (2). Second, we show the numerical attempt to model various flaring ARs, where we reproduce these four types (1-4) by conducting a series of flux-emergence simulations. We reveal that the sheared PILs in these ARs are created through the stretching and advection of horizontal magnetic fields due to the large-scale flux emergence. As ARs develop, free magnetic energy becomes stored in the corona, which could be released through the flare eruptions.

Biography: 2005-2009: B.S., U. of Tokyo; 2009-2014: Ph.D. U. of Tokyo; 2014-now: National Astronomical Observatory of Japan