  We explore the tail of various waiting time datasets of processes that follow
a nonstationary Poisson distribution with a sinusoidal driver. Analytically, we
find that the distribution of large waiting times of such processes can be
described using a power law slope of -2.5. We show that this result applies
more broadly to any nonstationary Poisson process driven periodically. Examples
of such processes include solar flares, coronal mass ejections, geomagnetic
storms, and substorms. We also discuss how the power law specifically relates
to the behavior of driver near its minima.
