Abstract
A new determination of the granular and intergranular velocities is described, based on a new approach. The method involves measurement of the granule/intergranule contrast as a function of wavelength on a sequence of filtergrams taken with the CSIRO computer-controlled 1/8 Å filter in the photospheric line Fe i λ6569.2. A procedure based on a simple but realistic morphological model of the granulation pattern is used to correct for spatial smearing. The effects of spectral smearing and of scattered light are also taken into account.
The present observations reveal a one hundred per cent correlation between brightness and the sense of the vertical velocity component and thus demonstrate beyond doubt the convective origin of the granulation. The new measurements yield a value of ≈1.8 km s−1 for the difference between the upward and downward velocities associated with an average granule. With certain plausible assumptions this leads to granular and intergranular velocities of ≈0.7 km s−1 (upward) and ≈1.1 km s−1 (downward) respectively.
Estimates are also obtained for the (true) central intensities and line broadening parameters of the line profile, separately for the average granule and intergranular lane.
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Bray, R.J., Loughhead, R.E. & Tappere, E.J. Convective velocities derived from granule contrast profiles in Fe i λ 6569.2. Sol Phys 49, 3–18 (1976). https://doi.org/10.1007/BF00221481
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DOI: https://doi.org/10.1007/BF00221481