Damping and frequency reduction of the f-mode due to turbulent motion in the solar convection zone

Solar f-mode properties were observed recently with high accuracy using high-resolution Michelson Doppler Imager (MDI) data from SOHO (Duvall et al. 1998). According to these observations, linewidths increase with wavenumber k and the f-mode frequency ω is significantly lower than the frequency ω0 given by the simple dispersion relation ω2 0 = gk. This paper provides a possible explanation of these observations on the basis of the turbulent flow that is in the convection zone. The f-mode spends more time propagating against the flow than with the flow. As a result, its effective speed and consequently frequency are reduced. This reduction is revealed by the real part of ω. A negative imaginary part of the frequency ω represents the damping of the coherent f-mode field due to scattering by the turbulent flow. The f-mode damping is a result of the generation of the turbulent field at the expense of the coherent field.