Mitigation of communication blackout with in-plane magnetic thin films

Abstract

The communications blackout problem encountered by objects rapidly traveling in atmosphere can be mitigated via the application of magnetic fields. Traditional (electro-)magnets used to generate strong out-of-plane fields to magnetize plasma sheaths can be large and heavy, limiting the benefits of the approach. This article investigates the potential use of magnetic material sheets magnetized in-plane to reduce material size requirements and make use of the material’s natural shape anisotropy. Via frequency bandwidth analysis, the existence of open communication bands due to applied in-plane magnetic fields is revealed. Numerical solvers are formulated to compute (i) the varying B fields applied in 3D space from source magnetization regions and (ii) signal attenuation through magnetized plasmas. Performing three numerical studies, it is found that the sizes and locations (in frequency space) of opened windows depend on the plasma profile, the transmitter location, and the material shape, and the magnetic configurations, which offer the greatest reduction in signal attenuation, can often be unintuitive. In addition, it is shown that it is possible to use arrays of smaller magnetic elements to emulate the performance of bulk material, enabling the use of modern thin-film magnetic materials. The presented analysis and numerical studies show that thin-film magnets are expected to be able to open windows to overcome communication blackout.