Abstracts Details


First Name * : Bo
Last Name * : Li
Affiliation * : Shandong University, China
Abstract Type * : Invited
Title * : Forward-modeling the Ultraviolet signatures of standing fast sausage modes in solar coronal loops
Author(s) * : Bo Li, Mijie Shi, Zhenghua Huang, Tom Van Doorsselaere, Shaoxia Chen
Abstract Session * : Solar flares and coronal mass ejections
Abstract * : Possible detections of standing fast sausage modes in solar coronal loops have been reported for a substantial number of passbands. However, their detailed signatures in ultraviolet (UV) have yet to be computed such that they can be more confidently identified. We examine how some representative Iron (Fe) lines are modulated by standing, linear, fast sausage modes (FSMs) in typical coronal loops by incorporating non-Equilibrium Ionization (NEI) in the computations of the relevant contribution functions. With Fe IX 171 and Fe XII 193 emissions from typical active region loops as examples, we show that in general NEI considerably impacts the intensity modulations, but shows essentially no effect on the Doppler velocities or widths. With reasonable wave amplitudes, the modulations in the line broadending are primarily due to wave-induced flows, resulting in a dominant periodicity of half the wave period. Some considerable difference arises when the Fe XXI 1354 line in typical flare loops is examined. With wave amplitude compatible with the recent IRIS measurements, we find that the line broadening is primarily modulated by temperature variations, and hence possesses a dominant periodicity of the wave period. We will also show that in general the wave damping rate can be reliably deduced from intensity modulations unless the loop temperatures are too far from the nominal line formation temperatures under the assumption of equilibrium ionization.