4.3 Giant cells

Reports on velocity field structures significantly larger than supergranulation were sporadic at best (Cram et al., 1983Hathaway et al., 1996Ulrich, 1998) until SOHO/MDI made detection of such long-lived and large scale features possible (Beck et al., 1998a,b). Data from SOHO/MDI also made a spherical harmonic analyses possible; Figure 4 of Hathaway et al. (2000Jump To The Next Citation Point) demonstrates conclusively that there is long-lived power at scales corresponding to spherical harmonic wave numbers ℓ ≤ 64; i.e., on scales larger than ∼ 100 Mm (cf. also Figure 22View Image).

Using local helioseismic techniques, flows on scales larger than supergranulation are now routinely detected and mapped (Hindman et al., 2004bFeatherstone et al., 2004Hindman et al., 2004aFeatherstone et al., 2006Hindman et al., 2006).

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