Low frequency oscillations trapped near the equator

Abstract

Two simple models illustrate the physical mechanism behind the trapping within a narrow band near the equator of low frequency, infinitesimal oscillations for which the motion is independent of longitude. A thin layer of liquid confined between two rotating spherical shells is in the first case homogeneous, in the second case stably stratified. In the equatorial ocean, one such oscillation would have a period of about ten days and be confined between 6° N and 6° S.