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 $E_{\mathrm{p}}$ with a low-energy spectral index $\alpha$ between -1 and -1.5, and an SSC component peaking at $E_{\mathrm{ssc}}$. 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 ${\sigma }_0\le 20$ can reproduce the MeV-TeV observations. This study underscores the value of combined MeV-TeV observations in probing GRB emission mechanisms.

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