Observations of the MHD waves allow determining physical parameters of coronal structures that cannot be directly measured, via a technique called coronal seismology. The flare-excited standing…

This federal contract award to the Catholic University of America (CUA) in Washington, D.C. is for a research project to investigate the physical nature and transport properties of flare-excited slow-mode waves in the solar corona. The $477,169 grant is funded by the National Aeronautics and Space Administration (NASA) and does not have a set-aside designation.

The project aims to determine the excitation, propagation, and damping mechanisms of these waves using observations from the Solar Dynamics Observatory (SDO) spacecraft. By applying coronal seismology techniques, the researchers seek to quantify thermal conduction and viscosity coefficients within hot solar flare plasma, which has implications for understanding energy release and transport processes. This research aligns with NASA's goal to "discover and characterize fundamental processes" in heliophysics.

Observations of the MHD waves allow determining physical parameters of coronal structures that cannot be directly measured, via a technique called coronal seismology. The flare-excited standing slow-mode waves were first discovered by soho/sumer through doppler shift oscillations in hot loops. However, the properties such as wave excitation, propagation, and dissipation are still poorly understood. Recently, SDO/AIA has detected longitudinal intensity oscillations in heated loops by flares. These oscillations show similar physical properties as previously detected by soho/sumer. By applying the coronal seismology method we have, for the first time, found quantitative evidence of thermal conduction suppression in a hot (>9 MK) loop (wang ET AL. 2015, apjl, 811, L13). This result has significant implications in two aspects: (1) conduction suppression suggests that the compressive viscosity is greatly enhanced to interpret the observed strong wave damping; (2) conduction suppression provides a reasonable mechanism for explaining the long-duration events where hot plasma detected in x-rays or EUV in many flares cools much slower than expected from the classical spitzer conductive cooling times. In this project, we propose to investigate the following scientific objectives motivated by our recent discovery: i) explore the physical nature of observed longitudinal oscillations, i.e., whether they are a reflecting propagating wave or a standing wave. What are the main factors that determine the excitation time of standing waves in coronal loops? II) determine transport coefficients such as thermal conduction and compressive viscosity coefficients from observed flare-excited slowmode waves dynamics by coronal seismology. III) investigate the theoretical effects and observational implications of the observationally determined effective transport coefficients on the wave excitation and damping mechanisms and the evolution of flare plasma. These objectives are relevant timely due to the need of quantitative understanding of solar flare energy release, and attainable thanks to the availability of SDO/AIA observations. Methodology: we will compile a catalog of 30-40 longitudinal oscillation events using SDO/AIA observations, identify the wave modes, and measure the excitation time of the standing waves. We will characterize the magnetic configuration and heating sources by calculating the magnetic topology from SDO/HMI data using the nonlinear force-free field (nlfff) extrapolation and by analyzing observations from SDO/AIA and rhessi. We will measure the thermal and wave properties of the flare loop. By applying the nonlinear, thermally conductive, and viscous 1D MHD numerical model in a parametric study we determine the effective transport coefficients from the model that best-fits the observed loop slow-mode oscillations. We will set up a 3D MHD model of ARS with initial magnetic configuration calculated by nlfff method from SDO/HMI and observed physical parameters. We use this model to study the effects of the effective transport coefficients on the excitation and damping of a standing slow wave, and cooling of flare loops. Relevance: the proposed investigation is to determine the unknown transport coefficients in the flare-heated AR loops, and based on these measurements to deal with the fundamental problems such as excitation and damping mechanisms of MHD waves and the energy transport processes in flare heating. The proposed analyses are thus in line with the decadal survey goal: "discover and characterize fundamental processes that occur both within the heliosphere and throughout the universe."