MHD of double-bands representing extended solar cycle

Abstract:

Along with the "butterfly diagram" of sunspots, combined observational studies of ephemeral active regions, X-ray and EUV brightpoints, plage, filaments, facule and prominences demonstrate a pattern, which is known as the Extended Solar Cycle (ESC). This pattern indicates the wings of the sunspot butterfly could be extended to much higher latitudes (about 60 degrees) and to earlier time than the start of a sunspot cycle, hence creating a strong overlap between cycles, meaning that, during the ongoing cycle's activity near 30-degrees latitude in each hemisphere, the next cycle is starting at around 60-degrees. By representing these epochs by oppositely-directed double magnetic bands in each hemisphere, we compute the eigen modes for MHD Rossby waves at the base of the convection zone and study how the properties of unstable MHD Rossby waves change as these band-pairs migrate equatorward. We find that the low-latitude band itself drives the major dynamics as the solar activity progresses from 35 to 20 degrees. When the activity proceeds further equatorward of 20 degrees, the next cycle's band from higher latitudes starts taking over to drive the majority of the activity features by interacting with the low-latitude band.