  Cometary activity is a manifestation of sublimation-driven processes at the
surface of nuclei. However, cometary outbursts may arise from other processes
that are not necessarily driven by volatiles. In order to fully understand
nuclear surfaces and their evolution, we must identify the causes of cometary
outbursts. In that context, we present a study of mini-outbursts of comet
46P/Wirtanen. Six events are found in our long-term lightcurve of the comet
around its perihelion passage in 2018. The apparent strengths range from $-0.2$
to $-1.6$ mag in a 5" radius aperture, and correspond to dust masses between
$\sim10^4$ to $10^6$ kg, but with large uncertainties due to the unknown grain
size distributions. However, the nominal mass estimates are the same order of
magnitude as the mini-outbursts at comet 9P/Tempel 1 and
67P/Churyumov-Gerasimenko, events which were notably lacking at comet
103P/Hartley 2. We compare the frequency of outbursts at the four comets, and
suggest that the surface of 46P has large-scale ($\sim$10-100 m) roughness that
is intermediate to that of 67P and 103P, if not similar to the latter. The
strength of the outbursts appear to be correlated with time since the last
event, but a physical interpretation with respect to solar insolation is
lacking. We also examine Hubble Space Telescope images taken about 2 days
following a near-perihelion outburst. No evidence for macroscopic ejecta was
found in the image, with a limiting radius of about 2-m.
