Modeling Dynamic and Steady Coronal Processes in the Alfven Wave Solar Atmosphere Model

MHD;Solar wind;Sun:corona;Sun:waves;techniques:spectroscopic;line:profiles;Atmospheric;Oceanic and Space Sciences;Science;Atmospheric, Oceanic & Space Science

Szente, JuditManchester IV, Ward B ;

University of Michigan

关键词: MHD;    Solar wind;    Sun:corona;    Sun:waves;    techniques:spectroscopic;    line:profiles;    Atmospheric;    Oceanic and Space Sciences;    Science;    Atmospheric, Oceanic & Space Science;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/145996/judithsz_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

This thesis presents a study of the solar wind acceleration and coronal plasma heating withtechniques that use both observational data and magnetohydrodynamic (MHD) simulations. Its focus is estimating the mass, momentum, and energy transport from the chromosphere to the solar corona under different conditions, both at small scales, by building an MHD model of a coronal jet, and at global scales, by computing synthetic spectra.The first part of the thesis estimates how much coronal jets contribute to the solar wind outflow and study their effect on the global corona. We present the computational implementation of a coronal jet into the two-temperature Alfvén Wave Solar Atmosphere Model (AWSoM) within the Space Weather Modeling Framework (SWMF). This is the first jet simulation implemented within a realistic, physically self-consistent global solar coronal model. We describe the interaction of the jet with the background solar-wind plasma and find that the large-scale corona is affected significantly by the outward propagating torsional Alfvén waves generated by our polar jet, across 40 degrees in latitude and out to 24 solar radii. We compare the physical properties and dynamic behavior of the polar jet to observations using line-of-sight synthetic images at EUV and X-ray bands, and find very close matches in terms of physical structure, dynamics, and emission. We conclude that even though jets interact with a large volume of coronal plasma, their contribution to the above-mentioned transport processes is much smaller than the average backgroundsolar-wind contribution. Also, it shows that jets introduce disturbances to the solar wind that can be detected by the Parker Solar Probe in-situ instruments during the close approaches of the spacecraft to the Sun.The second part of the thesis compares observational and synthetic spectra of the quietSun. It presents the implementation of SPECTRUM, which is a post-processing tool within SWMF, that predicts the solar spectrum providing line profiles for any user-defined line of sight. SPECTRUM takes into account Doppler shift, thermal broadening, anisotropic proton and electron temperatures, and the broadening due to low-frequency Alfvén waves. It can also apply instrument response function and instrumental broadening for any instrument.We use the three-temperature AWSoM model to obtain synthetic spectral observations of three different observational sites. Comparing the predicted spectra with Hinode/EIS observations, the model shows less significant wave damping in the low corona region,below 2 solar radii, and the observed effective velocity profiles are not explained by the solely Alfvén-wave driven coronal model.The measured quiet-Sun emission measure (EM) and differential emission measure (DEM) curves with predictions determined from output plasma parameters of AWSoM are compared, just as line-of-sight narrowband images. SPECTRUM shows as a more rigorous model validation tool than only comparing to line-of-sight images and 1 AU in-situ observations, and that it allows us to predict observables for upcoming future missions (Solar Orbiter). At the same time, SPECTRUM also enables scientists to utilize AWSoM predictions to carry out in-depth, quantitative studies of the physics of solar corona heating and wind acceleration. With these additions to the AWSoM model and the SWMF, we extended the platform to study the dynamic and quiet solar corona. These are significant steps towards understanding the phenomena of coronal heating and solar wind acceleration.