Compact VLF antenna surrounded with a magnetized plasma shell

Summary form only given. Experimental investigations of an electric dipole surrounded with a magnetized plasma shell show that the antenna system can be matched with a feeding line in a wide frequency range near the lower-hybrid frequency. As a result, in the presence of the plasma shell the power radiated by the antenna grew by almost three orders as compared to radiation of the dipole without plasma. It has been shown that the input antenna reactance vanishes to zero at some resonant density of the plasma shell. The antenna has an inductive input reactance at higher plasma densities and a capacitive reactance at lower densities. The field structure inside the plasma shell and in the near zone of the antenna has been extensively investigated. It has been shown that the antenna radiates both as electric and magnetic dipoles. Nonlinear effects in the plasma shell have been studied. It is shown that when increasing the high-frequency power the matching is shifted in dense plasma. The experimental results have been qualitatively interpreted in the framework of an idealized model of the slow mode of a magnetized plasma cylinder. The obtained experimental results are promising for making compact low frequency antennas.