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Modeling the generation, propagation, and dissipation of MHD waves in flaring coronal loops

Presentation #107.07 in the session Coronal Heating: Present Understanding and Future Progress II.

Published onOct 20, 2022
Modeling the generation, propagation, and dissipation of MHD waves in flaring coronal loops

Magnetosonic waves associated with flares were observed in coronal loops using various EUV bandpasses, as well as using spectral Doppler observations (i.e., SOHO/SUMER, TRACE, SDO/AIA, Hinode). The mechanisms that lead to the excitation and dissipation magnetosonic waves are still debated, and impact the understanding of coronal loops’ magnetic and thermal structures, as well as coronal heating processes. Guided by the EUV observations we develop a 3D magnetohydrodynamic (MHD) visco-resistive model with radiation, heat conduction, and empirical heating terms. Recent studies show that the dissipation coefficients in hot loop depart from classical values. We investigate the effects of viscosity, and heat conduction coefficients on the propagation and dissipation of magnetosonic waves. We study various wave excitation mechanisms, such as a velocity pulse at the footpoint of the loop at the coronal lower boundary. We find that the excitation by flow injection leads to the generation of primarily slow magnetosonic waves coupled nonlinearly to small amplitude fast magnetosonic waves in then coronal loop. We find significant leakage of the waves from the hot coronal loops with a small effect of viscous dissipation in cooler (6MK) loops, and more significant effects of viscous dissipation in hotter (10.5MK) coronal loops. We also confirm with the 3D MHD model that the significantly enhanced viscosity facilitates the quick formation of a standing slow mode and greatly suppresses the effects of nonlinearity as suggested in our previous studies based on 1D nonlinear MHD simulations. We investigate the effects of various forms of empirical heating profiles in the model active region on the loop thermal structure and wave propagation/dissipation. Our results demonstrate that nonlinear 3D MHD visco-resistive and thermally conductive models provide a useful tool to study the various MHD wave couplings, standing wave formation, leakage, and coronal loop wave heating.

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