SSC 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 $\sigma_0$ 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 $E_{\rm p}$ with a low-energy spectral index $\alpha$ between -1 and -1.5, and an SSC component peaking at $E_{\rm ssc}$. At high energies, Klein-Nishina 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 $\alpha\sim-1$ indicate a large Y parameter and strong KN suppression. We find a positive correlation between Y and $\sigma_0$, contrasting with internal shock model predictions. Applied to GRB 221009A, our model suggests $\sigma_0\leq20$ can reproduce the MeV-TeV observations. This study underscores the value of combined MeV-TeV observations in probing GRB emission mechanisms.