Magnetar-binary weather in hyperactive repeating fast radio bursts: A time-dependent plasma-environment model for RM flares, polarization stability, and extreme repetition

We present a time-dependent magnetar-binary weather framework for hyperactive repeating fast radio bursts (FRBs). The burst engine is treated phenomenologically as a magnetar, while a companion-supplied magnetized plasma environment regulates Faraday rotation, polarization transport, transparency, visibility, and apparent activity. We distinguish orbital climate, the deterministic phase-connected contribution of a wind, disk, or shocked sheath, from weather, the stochastic contribution of sectors, filaments, streamers, and eruptive magnetized structures. We test three nested models: M0, a smooth or isolated local environment; M1, deterministic binary climate; and M2, climate plus localized weather. The comparison uses a joint multi-observable likelihood for rotation measure (RM), dispersion measure (DM), linear and circular polarization, width, bandwidth, activity diagnostics or exposure-corrected rates where available, and transparency constraints, with model preferences summarized using the Bayesian information criterion (BIC). FRB 20220529 provides the strongest eruptive-weather test: its RM reached 1 9 7 7 ± 8 4 ⁢ r ⁢ 𝑎 ⁢ 𝑑 𝑚 − 2 and recovered in about two weeks, with M2 favored over M1 by Δ ⁢ B ⁢ 𝐼 ⁢ 𝐶 = 5 9 6 . 8 . FRB 20240114A is best described as a slow structured-sector crossing, with M2 favored by Δ ⁢ B ⁢ 𝐼 ⁢ 𝐶 = 1 3 8 . 3 ; its detected counts are retained only as catalog activity diagnostics because complete observing-window metadata are unavailable. FRB 20201124A is climate-compatible but not weather-required in the daily products; the reported 26.24 ± 0.02 day RM periodicity provides independent support for an orbital-climate interpretation. For FRB 20220529, the weak DM response gives a conservative lower limit of order 0.8 mG on the coherent line-of-sight field. The framework unifies RM drift, RM flares, and RM periodicity as dynamical limits of a binary-controlled plasma environment.