NONLOCAL AND NONLINEAR EFFECTS ON SOLAR OSCILLATIONS (RADIATIVE DAMPING, LIMB DARKENING).
AuthorLOGAN, JERRY DAVID.
AdvisorHill, Henry A.
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PublisherThe University of Arizona.
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AbstractThis work investigates the response of the solar atmosphere to mechanical and thermal driving due to global solar oscillations. It was discovered that the coupling of thermal and mechanical modes was very important in reconciling theoretical predictions of the expected change in the solar limb due to solar oscillations and experimental observations of the variability in the solar limb darkening function undertaken at SCLERA (Santa Catalina Laboratory for Experimental Relativity). The coupling between the thermal and mechanical modes occur mainly due to the nonlocal nature of the radiation field. Previous theoretical calculations that used approximations for the radiative transfer that ignored the nonlocal nature of the radiation field predicted expected temperature perturbations (compared to the fluid displacement) that were much too small to be observed. Much larger ratios were found when the radiative transfer was treated properly. A particular solar oscillation can be influenced by the presence of a large number of other modes, if these modes can change the average properties of the medium. If the basic nonlinear equations are statistically averaged, the influence of the "mean field" can be investigated. This nonlinear effect can become important in the analysis for single modes in the upper photosphere.