Modeling and experimental study of low-frequency electromagnetic wave propagation in cylindrical enveloping plasma produced by a shock tube

A promising solution has been proposed to overcome blackout using the magnetic field component of low-frequency electromagnetic waves to transmit a small amount of critical data. The principle of the method is that the magnetic-field attenuation is less than the electric-field attenuation for low-frequency electromagnetic waves in electrically small plasma. This paper presents an experiment based on a shock tube to verify the theory. Analytical expressions of SE and SH suitable for a shock-tube cylindrical model are derived using an equivalent circuit, which is used to describe the different forms of attenuation of electric and magnetic fields. For comparison, numerical simulations are conducted with varying plasma parameters. In the experiment, low-frequency electromagnetic waves penetrate the plasma produced by the shock tube from the test section, and measurements are made by field-strength probes at the center of the plasma flow field. A difference between SH and SE is found in both the experiment and theoretical simulation, with |SH| being less than |SE| by 20–30 dB when the frequency of low-frequency electromagnetic waves is 10 MHz. The verification of this theory thus shows that the magnetic field component of the low-frequency electromagnetic waves may potentially be used to transmit a small amount of critical data or vocal communication, allowing continuous communication during a period of radio blackout.