Saturation Characteristics of Multi‐Band EMIC Waves in the Inner Magnetosphere and Observational Evidence for the Second Saturation Process

Abstract The wave amplitude is vital for quantifying the impact of electromagnetic ion cyclotron (EMIC) waves on inner magnetospheric dynamics. Previous numerical studies mainly focused on the evolution of total wave energy/amplitude, whose maximum is usually modeled as a function of initial conditions. Recent quasilinear theory analysis shows existence of a second saturation of multi‐band EMIC waves which exhibits a dip of the total amplitude, emphasizing the need for more precise band‐specific models. Through one‐dimensional hybrid simulations, we reproduce the second saturation phenomenon and separately model wave characteristics for H + ‐ and He + ‐bands waves, including the maximum amplitudes and the time to maximum as a function of the initial maximum growth rate. Moreover, new parameters for the anisotropy‐beta inverse correlation of hot protons are obtained at the second saturation stage. We further present an in situ observation that first demonstrates the existence of the second saturation.