Synthetic Extreme-ultraviolet Emissions Modulated by Leaky Fast Sausage Modes in Solar Active Region Loops
Year: 2019
Type: article
Abstract: We study the extreme-ultraviolet (EUV) emissions modulated by leaky fast sausage modes (FSMs) in solar active region (AR) loops and examine their observational signatures via spectrometers like the EUV imaging spectrometer (EIS). After computing fluid variables of leaky FSMs with magnetohydrodynamic (MHD) simulations, we forward-model the intensity and spectral properties of the Fe x 185 Å and Fe xii 195 Å lines by incorporating nonequilibrium ionization (NEI) in the computations of the relevant ionic fractions. The damping times derived from the intensity variations are then compared with the wave values, namely, the damping times directly found from our MHD simulations. Our results show that in the equilibrium ionization cases, the density variations and the intensity variations can be either in phase or in antiphase, depending on the loop temperature. NEI considerably impacts the intensity variations but has only marginal effects on the derived Doppler velocity or Doppler width. We find that the damping time derived from the intensity can largely reflect the wave damping time if the loop temperature is not drastically different from the nominal formation temperature of the corresponding emission line. These results are helpful for understanding the modulations to the EUV emissions by leaky FSMs and hence helpful for identifying FSMs in solar AR loops.
Source: The Astrophysical Journal
Authors: Mijie Shi, Bo Li, Zhenghua Huang, Shao-Xia Chen
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2969697064