Magnetohydrodynamic instabilities of double magnetic bands in a shallow-water tachocline model. I. Cross-equatorial interactions of bands

This pattern indicates that the wings of the sunspot butterfly could be extended to much higher latitudes (up to similar to 60 degrees), to an earlier time than the start of a sunspot cycle, hence yielding a strong overlap between cycles.

Thus, during the ongoing cycle's activity near 30 degrees latitude in each hemisphere, the next cycle kicks off at around 60 degrees. By representing these epochs of overlaps by oppositely directed double magnetic bands in each hemisphere, we compute the unstable eigenmodes for MHD Rossby waves at the base of the convection zone and study how the properties of these energetically active Rossby waves change as these band pairs migrate equatorward.