The Use of Magnetic Fields in the Elimination of the Re-Entry Radio Blackout

This paper reviews first the most significant results concerning wave propagation through the plasma sheath surrounding a re-entering missle; second, it presents a new evidence showing that the re-entry radio blackout can be eliminated when a static magnetic field of the order of 500 Gauss is applied through the sheath. The evidence is based on the results of an analysis of transmission and reflection losses taking place at a plasma-air interface. The analysis also shows that in the special case of the absence of collisions, (v=0) maximum transmission occurs when the signal frequency (¿) is half the gyrofrequency (¿b); the ratio of transmitted to incident power, in this case, equals approximately the ratio of gyro to plasma frequency. This result is also shown to hold when collisions are present, provided that v2<<(¿b-¿)2.