CONVECTION: PERIODIC DUE TO r-MODES

摘要

Convection in a rotating fluid can acquire a periodic component where the convective timescale becomes comparable to or longer than the rotation period. Then, each local convective event becomes a source of Rossby-like oscillations. They carry off information that, in a spherical shell, can sum much later to stimulate an echo of the initial convective event. The two series of echos most likely to be detectable occur at intervals of six and 30 rotation periods and apply to events of large horizontal size. The waves can also impose other periodicities on the convection, and about a dozen in the range 75-800 days are clearly identified by comparing known regularities in solar activity with theoretical beat frequencies of global oscillations (r-modes).