Active Decoupling of Signal and Turbulence in Reentry Plasma Sheath via Dynamically Tuned Magnetic Field

During atmospheric reentry, a spacecraft is enveloped by a turbulent plasma sheath that induces severe signal degradation and communication blackout. Conventional mitigation strategies primarily focus on reducing average attenuation but fail to address the dynamic fluctuations in plasma density (typically 20–40%), which cause significant group velocity dispersion (GVD), pulse broadening, and intersymbol interference. To overcome this limitation, this paper proposes an active decoupling framework that dynamically tunes an external magnetic field to suppress turbulence-induced signal distortion in the reentry plasma sheath. By establishing a wave propagation model for right-hand circularly polarized (RCP) waves in magnetized collisional plasma and introducing a sensitivity analysis of propagation parameters with respect to plasma density fluctuations, we derive the condition under which the first-order sensitivity of GVD vanishes. Under this condition, a dynamic balance between collisional effects and frequency detuning renders the system immune to density perturbations, effectively decoupling signal transmission from plasma turbulence. Numerical simulations demonstrate that, under optimal parameter matching satisfying the dispersion immunity condition (Δω02=3νe2), pulse broadening can be suppressed by several orders of magnitude, and the broadening factor remains near unity over extended propagation distances. It is further shown that this optimal condition is highly sensitive to plasma parameter evolution, motivating the necessity of adaptive magnetic field control in dynamically evolving reentry environments. This work provides a novel physical-layer paradigm for mitigating reentry blackout by actively decoupling signals from turbulence via dynamically tuned magnetic fields.