Solar Hydrodynamics

Åke Nordlund, Niels Bohr Institute, University of Copenhagen

Solar hydrodynamics is one of the cases where numerical simulations of Eulerian dynamics have produced some of the most precise results. The dominant scale of convective motion near the solar surface produces the characteristic “granulation” radiation intensity pattern. The corresponding velocity field broadens spectral lines significantly, and the convective correlation of velocity and temperature causes spectral lines to be asymmetric and blue shifted. The observed widths, shifts, and asymmetries of solar spectral lines constitute a set of fingerprints that are well matched by high resolution numerical models, provided a realistic equation of state is used and the radiative losses at the surface are adequately modeled. Models and observations of larger scale motions reveal a spectrum of horizontal velocities that is approximately linear in horizontal wavenumber.

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