Wave propagation in the magnetic sun
ABSTRACT This paper reports on efforts to simulate wave propagation in the solar interior. Presented is work on extending a numerical code for constant entropy acoustic waves in the absence of magnetic fields to the case where magnetic fields are present. A set of linearized magnetohydrodynamic (MHD) perturbation equations has been derived and implemented.
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ABSTRACT: The described investigation is concerned with the solution of the non-LTE optically thick transfer equations for hydrogen, carbon, and other constituents to determine semiempirical models for six components of the quiet solar chromosphere. For a given temperature-height distribution, the solution is obtained of the equations of statistical equilibrium, radiative transfer for lines and continua, and hydrostatic equilibrium to find the ionization and excitation conditions for each atomic constituent. The emergent spectrum is calculated, and a trial and error approach is used to adjust the temperature distribution so that the emergent spectrum is in best agreement with the observed one. The relationship between semiempirical models determined in this way and theoretical models based on radiative equilibrium is discussed by Avrett (1977). Harvard Skylab EUV observations are used to determine models for a number of quiet-sun regions.The Astrophysical Journal Supplement Series 05/1981; · 16.24 Impact Factor
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ABSTRACT: We report on realistic simulations of solar surface convection that are essentially parameter-free, but include detailed physics in the equation of state and radiative energy exchange. The simulation results are compared quantitatively with observations. Excellent agreement is obtained for the distribution of the emergent continuum intensity, the profiles of weak photospheric lines, the p-mode frequencies, the asymmetrical shape of the mode velocity and intensity spectra, the p-mode excitation rate, and the depth of the convection zone. We describe how solar convection is non-local. It is driven from a thin surface thermal boundary layer where radiative cooling produces low entropy gas which forms the cores of the downdrafts in which most of the buoyancy work occurs. Turbulence and vorticity are mostly confined to the intergranular lanes and underlying downdrafts. Finally, we present some preliminary results on magneto-convection.Solar Physics 02/2000; 192(1):91-108. · 3.26 Impact Factor
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ABSTRACT: The key to local helioseismology is the eective appli- cation of local seismic diagnostic techniques to deter- mine the structure of the solar interior with the finest possible resolution. The extent and magnitude of the supergranular return flow and the nature of thermal anomalies, flows, and magnetic-field configurations in and near active regions are phenomena on which we hope local helioseismic analyses will shed clear light. However, current applications of local seismic methods produce ambiguous and inconsistent inter- pretations. It is clear that in order to make further progress, evaluation and refinement of local analysis techniques, and the development of procedures that can separate magnetic eects, subsurface flows, and sound-speed variations will prove critical. We be- lieve substantial progress in this area can be made by conducting control experiments based on magneto- acoustic-gravity waves propagating through specified models of subphotospheric anomalies. In this paper we describe the need for such an eort and devel- opments currently under way to produce the tools necessary to implement a validation and testing pro- gram.09/2004; 559:172.