Damping and frequency reduction of the f -mode due to turbulent motion in the solar convection zone
M. Medrek 1,
K. Murawski 1 and
B. Roberts 2
Received 12 February 1999 / Accepted 5 July 1999
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 is significantly lower than the frequency given by the simple dispersion relation . 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 . A negative imaginary part of the frequency 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.
Key words: convection Sun: atmosphere Sun: granulation Sun: oscillations turbulence
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© European Southern Observatory (ESO) 1999
Online publication: August 25, 1999