Sketch of a slender magnetic flux tube in equilibrium in the equatorial plane of a late-type main-sequence star (solid green line). The xy plane is the equatorial plane of the star as seen from the north pole. The barycenter of the star is O, its radius is R_s, and r₀ is the radius of the unperturbed flux tube. The convective zone of the star is rendered in yellow, and the radiative zone, including the overshoot layer where the flux tube is located, is rendered in white. The flux tube perturbed by an oscillation mode with azimuthal wavenumber m = 8 is plotted as a solid black line.