Time-dependent models for blazar emission with the second-order fermi acceleration

Katsuaki Asano, Fumio Takahara, Masaaki Kusunose, Kenji Toma, Jun Kakuwa

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54 Citations (Scopus)


The second-order Fermi acceleration (Fermi-II) driven by turbulence may be responsible for the electron acceleration in blazar jets. We test this model with time-dependent simulations. The hard electron spectrum predicted by the Fermi-II process agrees with the hard photon spectrum of 1ES 1101-232. For other blazars that show softer spectra, the Fermi-II model requires radial evolution of the electron injection rate and/or diffusion coefficient in the outflow. Such evolutions can yield a curved electron spectrum, which can reproduce the synchrotron spectrum of Mrk 421 from the radio to the X-ray regime. The photon spectrum in the GeV energy range of Mrk 421 is hard to fit with a synchrotron self-Compton model. However, if we introduce an external radio photon field with a luminosity of 4.9 × 1038 erg s-1, GeV photons are successfully produced via inverse Compton scattering. The temporal variability of the diffusion coefficient or injection rate causes flare emission. The observed synchronicity of X-ray and TeV flares implies a decrease of the magnetic field in the flaring source region.

Original languageEnglish
Article number64
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 2014 Jan 1


  • acceleration of particles
  • BL Lacertae objects: individual (1ES 1101-232, Mrk 421)
  • radiation mechanisms: non-thermal
  • turbulence


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