Convective velocities derived from granule contrast profiles in Fe I at 6569.2 A

Details Convective velocities derived from granule contrast profiles in Fe I at 6569.2 A Convective velocities derived from granule contrast profiles in Fe I at 6569.2 A

Jul 1976

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1976soph...49....3b&link_type=abstract

Solar Physics, vol. 49, July 1976, p. 3-18.

Physics

15

Convective Flow, Flow Velocity, Iron, Photosphere, Solar Granulation, Astronomical Photography, Computer Techniques, Filtergrams, Image Contrast, Line Spectra, Solar Atmosphere, Spectral Line Width

Scientific paper

A method for determining the velocity difference between upwardand downward-moving photospheric granules and intergranular material is described which involves measuring the contrast of a number of granules as a function of wavelength during tuning across the photospheric Fe I line at 6569.2 A. This approach is made possible by the introduction of the 'tuned-filtergram' technique, whereby a narrow-band filter is used to take a sequence of nearly simultaneous photographs at several wavelengths across the chosen line. Spatial smearing is corrected through a procedure based on a simple but realistic morphological model of the granulation pattern, and effects of spectral smearing as well as scattered light are also taken into account. After correction for instrument effects, the contrast measurements are found to yield a value of about 1.8 km/s for the difference between the upward and downward velocities associated with an average granule; this figure leads to granule and intergranular velocities of about 0.7 km/s (upward) and 1.1 km/s (downward), respectively, on the basis of certain plausible assumptions. True central intensities and line-broadening parameters of the selected Fe I line are estimated separately for the average granule and its intergranular lane.

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