  The Compton Gamma Ray Observatory revealed the high energy emission of some
Active Galactic Nuclei called "Blazars"; few of them have also been observed by
ground Cererenkov arrays. Those sources observed with Whipple Observatory emit
gamma rays up to few TeV. From the spectral data and variability measurements,
a purely electrodynamical description of this emission can be proposed,
provided that it comes from relativistic flares at the beginning of the jet.
Because of the source compacity, the creation of electron-positron pairs and
their escape from the black hole environment could likely explain the shape of
the spectra. A plasma dominated by relativistic electrons (positrons) close to
equipartition with the magnetic field is a suitable acceleration medium that
can account for both the required high Lorentz factors and the short
variability.
