The aircrafts, such as space shuttle, spaceship and so on, are facing the well-known blackout problem when they reentry into the atmosphere. The plasma sheath leads electromagnetic waves to attenuation, and the communications between the aircrafts and the ground to losing, and even completely interrupte, thereby resulting in the loss of radar targets and threatening the lives of the astronauts. Therefore, it is important to study the properties of the electromagnetic wave transmission in plasma. The characteristics of electromagnetic wave transmission in plasma are studied theoretically and experimentally in this paper. The variations of the electromagnetic wave attenuation with plasma density, collision frequency and electromagnetic wave frequency are obtained. The electromagnetic wave attenuation increasean an order of magnitude with plasma density increasing an order of magnitude. The electromagnetic wave attenuation first increases and then decreases with plasma collision frequency increasing, the electromagnetic wave attenuation decreases with the increase of electromagnetic wave frequency. The electromagnetic wave transmission properties in plasma are studied experimentally with shock tube, and the experimental results accord well with the theoretical results. The results show that increasing the electromagnetic wave frequency is an effective way to solve the reentry blackout problem.
This article integrate the theoretical calculation of the power-frequency electromagnetic field intensity and radio interference intensity under transmission line, and analyze the factor which influence the value and distribution of the electromagnetic field, radio interference under transmission line, aiming to provide basis and reference for other environmental assessment of electromagnetism. The study shows that a reasonable selection of analog lines can get an accurate result as the theoretical calculation. Important factors of analog lines selection including: grade of voltage, current, height of line, location order of line, number of circuit, section area of line, number of bundle conductors.
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