  The detection of a long flaring activity from blazar TXS 0506+056 in temporal
and spatial coincidence with the energetic neutrino IceCube-170922A provided
evidence about the photo-hadronic interactions in this source. However,
analysis of the archival neutrino and multi-wavelength data from the direction
of this blazar between September 2014 and March 2015 revealed a "neutrino
flare" without observing quasi-simultaneous activity in the gamma-ray bands,
posing challenges to established models. Electron-positron ($e^\pm$) pairs
generated from the accretion disks have been amply proposed as a mechanism of
bulk acceleration of sub-relativistic and relativistic jets. These pairs
annihilate inside the source producing a line around the electron mass which is
expected to be blueshifted in the observed frame (on Earth) and redshifted in
the frame of the dissipation region of the jet. The redshifted photons in the
dissipation region interact with accelerated protons, producing high-energy
neutrinos that contribute significantly to the diffuse neutrino flux in the
$\sim$ 10 - 20 TeV energy range in connection with gamma-rays from photo-pion
process which can be detected by future MeV orbiting satellites. Based on this
phenomenological model we can explain the "neutrino flare" reported in
2014-2015.
