Synchrotron Self-Compton Radiation in the ICMART Model: Spectral Simulations and Application to the Record-breaking GRB 221009A

Abstract This paper presents simulations of the synchrotron self-Compton (SSC) spectrum within the Internal-Collision-induced Magnetic Reconnection and Turbulence (ICMART) model. We investigate how key parameters like the magnetization σ 0 shape the broadband spectral energy distribution by regulating the electron distribution and magnetic field strength. The overall spectrum typically comprises two components: synchrotron radiation peaking at E p with a low-energy spectral index α between −1 and −1.5 and an SSC component peaking at E ssc . At high energies, Klein–Nishina (KN) suppression causes an exponential cutoff. The flux ratio Y between these components is critical: when Y is small, the SSC peak can be suppressed. Spectral features of the synchrotron component reveal the underlying physical conditions: harder spectra with α ∼ −1 indicate a large Y parameter and strong KN suppression. We find a positive correlation between Y and σ 0 , contrasting with internal shock model predictions. Applied to GRB 221009A, our model suggests σ 0 ≤ 20 can reproduce the MeV–TeV observations. This study underscores the value of combined MeV–TeV observations in probing gamma-ray burst emission mechanisms.