  We observe the abrupt end of solar activity cycles at the Sun's equator by
combining almost 140 years of observations from ground and space. These
"terminator" events appear to be very closely related to the onset of magnetic
activity belonging to the next sunspot cycle at mid-latitudes and the
polar-reversal process at high-latitudes. Using multi-scale tracers of solar
activity we examine the timing of these events in relation to the excitation of
new activity and find that the time taken for the solar plasma to communicate
this transition is of the order of one solar rotation, but could be shorter.
Utilizing uniquely comprehensive solar observations from the Solar Terrestrial
Relations Observatory (STEREO), and Solar Dynamics Observatory (SDO) we see
that this transitional event is strongly longitudinal in nature. Combined,
these characteristics imply that magnetic information is communicated through
the solar interior rapidly. A range of possibilities exist to explain such
behavior: the presence of magnetic reconnection in the deep interior, internal
gravity waves on the solar tachocline, or that the magnetic fields present in
the Sun's convection zone could be very large, with a poloidal field strengths
reaching 50k - considerably larger than conventional explorations of solar and
stellar dynamos estimate. Regardless of mechanism responsible, the rapid
timescales demonstrated by the Sun's global magnetic field reconfiguration
present strong constraints on first-principles numerical simulations of the
solar interior and, by extension, other stars.
