  Models of Blazars based on the propagation of finite discontinuities or
fronts in the Poynting flux jet from the innermost regions of an accretion disk
around a black hole are discussed. Such fronts may be responsible for short
time-scale (from less than hours to days) flares in different wavebands from
high frequency radioband to TeV, with delay in low radio frequencies as a
result of synchrotron self-absorption. The cases of magnetic fields of one and
opposite polarities across the front are investigated. We find that
annihilation of magnetic field in the front leads to higher energy spectrum of
leptons and possibility of strong TeV flares. Electron-positron pairs form in
most cases as a result of interaction between numerous synchrotron photons and
SSC photons, and constitute the majority species, compared with the ions at
subparsec scales. Frequent weak outbursts may be responsible for flickering
core radiation in all wavebands, while the stronger outbursts may be observed
as short time-scale flares.
