2016/05/20 by Xianyong Bai, X. Y. Bai, Jiangtao Su +8
Physics and Astronomy · #Solar and Space Plasma Dynamics #Ionosphere and magnetosphere dynamics #Astro and Planetary Science
paper · doi:10.3847/0004-637x/823/1/60
ABSTRACT We report a subarcsecond penumbral transient brightening event with the high-spatial resolution observations from the 1.6 m New Solar Telescope (NST), Interface Region Imaging Spectrograph ( IRIS ), and the Solar Dynamics Observatory . The transient brightening, whose thermal energy is in the range of nanoflares, has signatures in the chromosphere, the transient region, and the corona. NST's H α channel reveals the fine structure of the event with a width as narrow as 101 km (0.″14), which is much smaller than the width from the previous observation. The transient brightening lasts for about 3 minutes. It is associated with a redshift of about 17 km s −1 , found in the Si iv 1402.77 Å line and exhibits an inward motion to the umbra with a speed of 87 km s −1 . The small-scale energy released from the event has a multi-temperature component. Spectral analysis of the brightening region from IRIS shows that not only the transition region lines such as Si iv 1402.77 Å and C ii 1334.53 Å, but also the chromospheric Mg ii k 2796.35 Å line are significantly enhanced and broadened. In addition, the event can be found in all the extreme-ultraviolet passbands of the Atmospheric Imaging Assembly and the derived differential emission measure profile increases between 4 and 15 MK (or 6.6 ≤ log T ≤ 7.2) in the transient brightening phase. It is possible that the penumbral transient brightening event is caused by magnetic reconnection.