Deciphering solar magnetic activity: The solar cycle clock

We will discuss the end point of that progression, dubbed "terminator" events, and our means of diagnosing them. In this paper we expand on the Extended Solar Cycle framework to construct a new solar activity "clock" which maps all solar magnetic activity onto a single normalized epoch based on the terminations of Hale Magnetic Cycles.

Defining phase 0*2 pi on this clock as the Terminators, then solar polar field reversals occur at similar to 0.2*2 pi, and the geomagnetically quiet intervals centered around solar minimum start at similar to 0.6*2 pi and end at the terminator, thus lasting 40% of the cycle length. At this onset of quiescence, dubbed a "pre-terminator," the Sun shows a radical reduction in active region complexity and, like the terminator events, is associated with the time when the solar radio flux crosses F10.7 = 90 sfu.