Thermal and mechanical damping of solar p-modes

Abstract

Nonadiabatic effects associated with the transfer of energy and with turbulent stresses add small imaginary parts, ω_i^(1) and ω_i^(2), to solar p-mode eigenfrequencies. Numerical calculations have shown that these quite different processes make comparable contributions to ωi at frequencies well below the acoustic cutoff at ω_(ac). We derive analytic expressions which reveal the connection between ω_i^(1) and ω_i^(2). Our estimates yield ω_i ∝ ω^8 for ω « ω_(ac), in good agreement with the numerical calculations. However, the observed line width is proportional to ω^(4.2) at low frequencies. We suspect that there is an unmodeled component of perturbed convective energy transport or of turbulent viscosity that makes an important contribution to ω_i at ω « ω_(ac).

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