  Very fast variability on scales of minutes is regularly observed in Blazars.
The assumption that these flares are emerging from the dominant emission zone
of the very high energy (VHE) radiation within the jet challenges current
acceleration and radiation models. In this work we use a spatially resolved and
time dependent synchrotron-self-Compton (SSC) model that includes the full time
dependence of Fermi-I acceleration. We use the (apparent) orphan $\gamma$-ray
flare of \textit{Mrk501} during MJD 54952 and test various flare scenarios
against the observed data. We find that a rapidly variable external radiation
field can reproduce the high energy lightcurve best. However, the effect of the
strong inverse Compton (IC) cooling on other bands and the X-ray observations
are constraining the parameters to rather extreme ranges. Then again other
scenarios would require parameters even more extreme or stronger physical
constraints on the rise and decay of the source of the variability which might
be in contradiction with constraints derived from the size of the black hole's
ergosphere.
