  M87 is the first detected non-blazar extragalactic Tera-Electron-Volt (TeV)
source with rapid variation and very flat spectrum in the TeV band. To explain
the two-peaks in the spectral energy distribution (SED) of the nucleus of M87
which is similar to those of blazars, the most commonly adopted models are the
synchrotron self-Compton scattering (SSC) models and the external inverse
Compton scattering (EIC) models. Considering that there is no correlated
variation in the soft band (from radio to X-ray) matching the TeV variation,
and the TeV sources should not suffer from the gamma-gamma absorption due to
the flat TeV spectrum, the EIC models are advantageous in modeling the TeV
emission from M87. In this paper, we propose a self-consistent EIC model to
explain the flat TeV spectrum of M87 within the framework of fully general
relativity, where the background soft photons are from the advection-dominated
accretion flow (ADAF) around the central black hole, and the high energy
electrons are from the mini-jets which are powered by the magnetic reconnection
in the main jet (Giannios et al. 2010). In our model, both the TeV flares
observed in the years of 2005 and 2008 could be well explained: the gamma-gamma
absorption for TeV photons is very low, even inside the region very close to
the black hole 20Rg~50Rg; at the same region, the average EIC cooling time (~
10^2-10^3s) is short, which is consistent with the observed time scale of TeV
variation. Furthermore, we also discuss the possibility that the accompanying
X-ray flare in 2008 is due to the direct synchrotron radiation of the
mini-jets.
