4.2 Supergranulation

Supergranulation was first observed by Hart (1956), and was later studied in more detail (and named) by Leighton et al. (1962) and by Simon and Leighton (1964), who emphasized the close correlation between the supergranulation and the chromospheric network.

A large number of works have studied supergranular scale flows observationally and tried to characterize them in terms of, for example, flow velocity as a function of cell size, morphology, clustering, advection of smaller scale flows, divergence and convergence, etc.; some of the most significant ones are, e.g, Deubner (1971); Muller et al. (1992Jump To The Next Citation Point); Hathaway et al. (2000Jump To The Next Citation Point); Zhao and Kosovichev (2003); Del Moro et al. (2004); DeRosa and Toomre (2004Jump To The Next Citation Point) and Meunier et al. (2007).

Numerical hydro- and MHD-simulations, with realistic equations of state and radiative energy transfer, are now reaching the scale of supergranulation (Rieutord et al., 2002Stein et al., 2006aJump To The Next Citation Point20052006bJump To The Next Citation PointUstyugov, 2006Stein et al., 2007bUstyugov, 20072008), and it is thus becoming possible to make quantitative comparisons between observations and simulations. A great benefit of this approach is that if a good match is obtained between the numerical simulations and observations, one may with some confidence use the numerical simulations as proxies or predictions of the subsurface and small scale structure. This allows, e.g., local helioseismology techniques to be further improved and calibrated (Georgobiani et al., 2004Zhao et al., 2007aGeorgobiani et al., 2007Jump To The Next Citation PointBirch et al., 2007).

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