Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002esasp.506..415a&link_type=abstract
In: Solar variability: from core to outer frontiers. The 10th European Solar Physics Meeting, 9 - 14 September 2002, Prague, Cze
Physics
2
Solar Faculae, Magnetic Elements, Solar Variabilities
Scientific paper
Digital processing is used to measure the contrast of solar faculae from a set of high resolution selected images observed at the R.B. Dunn's 76 cm clear aperture vacuum telescope of NSO-Sacramento Peak Observatory. Five ultra-narrow passbands from Red to Blue (Red, Hα, Mgbl, Green, Blue) were given by the UBF. The range of heliocentric distances covered by our measurements is 0.1 < μ = cosθ < 0.4 (θ ɛ 84°, 66°). About 104 facular "points" were measured over nearly 100 selected images. By averaging and normalizing the contrast of faculae and plotting them vs. heliocentric angle, we found that the contrast increases monotonically towards the limb for all wavelengths. The contrast increases as wavelength decreases. We did not introduce any correction for the smearing in our measurements, in order not to bias the results. In addition, we study the variations of integrated brightnesses or fluxes in order to discuss the flux contribution of faculae. Fluxes definitely show a peak value near μ = 0.25, and then a decrease towards the limb. The center limb effect of the shape-factor of facular elements is finally analyzed; the ratio of apparent sizes in the radial and in the tangential directions do not show the foreshortening effect expected to be observed over cell-like structures, suggesting that facular elements are structured by a small scale highly concentrated magnetic field and not just by the gravity.
Adjabshirizadeh Ali
Koutchmy Serge
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