Astron. Astrophys. 321, 323-329 (1997)

4. Meridional circulation

4.1. Net meridional circulation

We calculated the meridional circulation (referred to hereafter as "m.c.") of cycle 19 sunspots (Fig. 5). Our convention is a positive m.c. towards the North pole. The observed motions are equatorward at low latitudes (though hardly significant) and poleward at high latitudes, for both cycles. For comparison, net m.c. for cycle 21 is also shown. The m.c. pattern is more pronounced for cycle 19 sunspots, particularly in the case of low-latitude sunspots.

Fig. 5. Meridional circulation of cycle 19 (solid line) and cycle 21 (dashed line) sunspots. Error bars for cycle 19 are at the 1- confidence level

We considered the averaged m.c. per hemisphere for the whole cycle. We obtained 0.005 /day for the northern hemisphere and 0.016 /day for the southern hemisphere. These averages are hardly significant, because the pattern is latitude-dependent, directed toward one or the other pole. For this reason, it is not possible to use these averages to investigate the cycle variability of m.c. in detail.

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998
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