Peculiarities of solar photospheric convection at granular, mesogranular and supergranular scales
|1Baran, OA, 1Stodilka, MI |
1Astronomical Observatory of Ivan Franko National University of Lviv, Lviv, Ukraine
|Section: Solar Physics|
Power spectra of temperature and vertical velocity variations in the solar photosphere were calculated by using observational data of neutral iron line λ ≈ 639.3 nm obtained with the 70-cm German Vacuum Tower Telescope (Canary Islands, Spain) around the centre of the solar disc in the non-pertubed region. We analyzed the power spectra change with height. In the lower photosphere the main power is localized in the range corresponding to granulation with a peak at scales of about 1.5...2.0 Mm and decreases with height. In the upper photosphere maximum of the power spectrum is shifted towards larger scales ( Δλ ≈≤ 1 Mm); the power of vertical velocity fluctuations of supergranulation (λ ≈ 20...30 Mm) practically does not change with height; a separate regime of mesogranulaton (λ ≈ 5...12 Mm) was not found at all altitudes under study. Аccording to our results, the convective structure of the solar photosphere on mesogranular scales behaves like the granulation, namely, me-sostructures appear as a part of a broad distribution of granular scales. It is shown that supergra-nular flows are stable along the whole photosphere and reach much higher layers than the granular ones.
|Keywords: granulation, photosphere, Sun|