Abstract:
We investigate the occurrence of the “extended solar cycle” (ESC) as it occurs in a host of
observational data spanning 140 years. Investigating coronal, chromospheric, photospheric,
and interior diagnostics, we develop a consistent picture of solar activity migration linked to
the 22-year Hale (magnetic) cycle using superposed epoch analysis (SEA) and previously
identified Hale cycle termination events as the key time for the SEA. Our analysis shows
that the ESC and Hale cycle, as highlighted by the terminator-keyed SEA, is strongly recurrent throughout the entire observational record studied, some 140 years. Applying the same
SEA method to the sunspot record confirms that Maunder’s butterfly pattern is a subset of
the underlying Hale cycle, strongly suggesting that the production of sunspots is not the
fundamental feature of the Hale cycle, but the ESC is. The ESC (and Hale cycle) pattern
highlights the importance of 55◦ latitude in the evolution, and possible production, of solar
magnetism.
