Research on the Attenuation of Electromagnetic Waves Suppressed by Traveling Magnetic Fields in Plasma
M. M. Han, Zhenmei Li, Hui Zhou, Zhenyan Li, Guanghan Liu, Ziyuan Xu, Z L Liu
Abstract
When hypersonic flights or reentry vehicles enter the atmosphere, they are surrounded by the plasma sheath that can impede the propagation of electromagnetic (EM) waves, resulting in communication blackout. The current method of travelling magnetic field (TMF) reduces the high magnetic field strength required by the magnetic window method and mitigates communication blackout during reentry which can translate the requirement for magnetic field strength into a demand for TMF velocity. The magnetic field waveforms generated by multi-phase TMF generation devices are compared under different phase and magnetic spacing to select the more optimal generator structure, and its effect on the electron density of a nonuniform plasma is simulated, and the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> components were found to account for a relatively small part of the effect of TMF on plasma electron density. Further by fitting the expression for the magnetic field, a set of parameters describing the magnetic field can be obtained to analyze the changes in electron density of the plasma and the propagation characteristics of EM waves in the plasma under the action of the TMF, and the results of analyzing the TMF generated by the device through the fitted magnetic field method are in agreement with the simulation results. The results indicate that this device can effectively reduce plasma density by altering the velocity of the TMF through different frequency settings of the signal source. Furthermore, the TMF restrains the attenuation of EM waves effectively during their propagation in the plasma, and concrete analysis is conducted for typical frequency bands such as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> -, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -, and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> -bands. This article demonstrates the feasibility of applying TMF to mitigate the attenuation of EM waves in nonuniform plasma.