Determination of transport coefficients from flare-induced slow magnetoacoustic waves by parametric study
Abstract
Recent studies of slow-mode waves in a flaring coronal loop observed by SDO/AIA have revealed the suppression of thermal conduction and significant enhancement of compressive viscosity in hot (~ 10 MK) plasma (Wang et al. 2015, 2018). The strong suppression of thermal conduction may provide an explanation for the slower-than-expected cooling of flare plasma in the decay phase, while the anomalously enhanced viscosity can explain the quick formation of standing slow magnetosonic waves seen in observations. In this study we aim at developing a new coronal seismology tool for determining the transport coefficients in flaring loop plasma based on a parametrical study of wave properties. For this purpose we are using a 1D nonlinear MHD loop model in combination with the linear theory. We find that the classical thermal conductivity is suppressed by a factor of about 3 derived from the observed phase shift between temperature and density perturbations, and the classical viscosity coefficient is enhanced by a factor of 10 from the observed decay time. Using the 1D loop model with these refined transport coefficients, we study the excitation of slow-mode waves by launching a flow pulse from one footpoint. The simulation can self-consistently produce the fundamental standing wave on a timescale in agreement with the observation. We extend the model to more realistic 2.5D MHD and study the effects of the seismology-determined transport coefficients on the wave excitation and damping times using simulations of a field-aligned hydrodynamic loop model with impulsive heating. We model the impulsive excitation of slow magnetosonic waves in a bipolar coronal active region (AR) using 2.5D MHD model that includes a hot and dense loop initially in hydrostatic equilibrium. We discuss the effect of the loop's transverse and longitudinal inhomogeneity on the resulting wave dynamics.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSH33D3408W
- Keywords:
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- 7829 Kinetic waves and instabilities;
- SPACE PLASMA PHYSICS;
- 7835 Magnetic reconnection;
- SPACE PLASMA PHYSICS;
- 7836 MHD waves and instabilities;
- SPACE PLASMA PHYSICS;
- 7863 Turbulence;
- SPACE PLASMA PHYSICS