  We are presenting a detailed parameter study of the time-dependent electron
injection and kinematics and the self-consistent radiation transport in jets of
intermediate and low-frequency peaked BL Lac objects. Using a time-dependent,
combined synchrotron-self-Compton and external-Compton jet model, we study the
influence of variations of several essential model parameters, such as the
electron injection compactness, the relative contribution of synchrotron to
external soft photons to the soft photon compactness, the electron-injection
spectral index, and the details of the time profiles of the electron injection
episodes giving rise to flaring activity. In the analysis of our results, we
focus on the expected X-ray spectral variability signatures in a region of
parameter space particularly well suited to reproduce the broadband spectral
energy distributions of intermediate and low-frequency peaked BL Lac objects.
We demonstrate that SSC- and external-Compton dominated models for the
gamma-ray emission from blazars are producing significantly different
signatures in the X-ray variability, in particular in the soft X-ray light
curves and the spectral hysteresis at soft X-ray energies, which can be used as
a powerful diagnostic to unveil the nature of the high-energy emission from BL
Lac objects.
