selfCompton

SelfCompton, or synchrotron self-Compton (SSC), is a radiative process in which relativistic electrons scatter the photons they themselves emit via synchrotron radiation, boosting them to higher energies via inverse Compton scattering. The seed photons are the synchrotron photons produced by the same electron population, and the scattering typically occurs in a compact, magnetized region such as a jet or shock.

In the Thomson regime, the scattered photon energy is roughly ε_scat ≈ γ^2 ε_seed, with γ the electron Lorentz factor; the resulting spectrum depends on the electron distribution, magnetic field, and source size, while Klein–Nishina effects reduce efficiency at high energies. Observationally, SSC is a leading explanation for high-energy emission in blazar jets and other relativistic sources, producing the second broad peak in the spectral energy distribution; external Compton, by contrast, uses seed photons from outside the jet.

Modeling often adopts a one-zone, homogeneous approach with a power-law or broken-power-law electron distribution, a magnetic field B, a region size R, and a Doppler factor δ to account for relativistic beaming. Variability can be rapid, and coordinated multiwavelength campaigns frequently reveal correlated changes in both the synchrotron and high-energy components.

The term self-Compton is common in astrophysical literature and denotes SSC, distinct from generic self-scattering in other contexts. It is a key mechanism in interpreting the high-energy output of active galactic nuclei jets, gamma-ray bursts, and related sources.