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Long-lived giant cells detected at the surface of the Sun

Abstract

Giant convective cells have been predicted1 to exist in the Sun. Such cells should span the entire zone unstable to convective motions — now known to cover the outer 29 per cent of the Sun's radius2 — and could be dredging up the magnetic flux that is thought to be the source of solar activity (sunspots). Several studies3,4,5 have failed to detect these giant cells, although there have been hints6,7,8,9 of their existence. We have detected long-lived velocity cells, which we identify as the elusive giant convective cells, extending over 40–50 degrees of longitude but less than 10 degrees of latitude. The large aspect ratio (>4) is surprising (although predicted by one model10) and may be a consequence of the Sun's differential rotation, whereby features with a larger extent in latitude are broken up by rotational shear.

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Figure 1: Autocorrelation (a) and cross-correlation (b) of the time series for selected bins.
Figure 2: Maps of the east–west component of flow speed obtained by averaging over a disk passage.
Figure 3: The autocorrelation computed for the map of EPS Fig. 2 for the latitude 5± 5°.

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Acknowledgements

T.L.D. thanks P. Scherrer and the SOI group at Stanford for their hospitality during this work and for the use of their computing faciities, supported by NASA. SOHO is a mission of international cooperation between ESA and NASA. This work was supported in part by the Solar Physics Branch of the Space Physics Division of NASA.

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Correspondence to J. G. Beck.

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Beck, J., Duvall, T. & Scherrer, P. Long-lived giant cells detected at the surface of the Sun. Nature 394, 653–655 (1998). https://doi.org/10.1038/29245

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