Absorption of energy from a large amplitude electromagnetic pulse by a collisionless plasma

A series of experiments in which an electromagnetic pulse (EMP) is propagated through a nitrogen plasma are discussed. The pulse has the general characteristics of an EMP. The pulse is observed as it emerges from the plasma as a function of the plasma parameters. As the electron number density increases, it is found that energy is increasingly absorbed from the pulse, a process due to joule heating. In addition, at higher number densities, ringing of the pulse occurs. The nitrogen pressure in these experiments is sufficiently low so that collisions play only a minor role. Also developed is a theoretical model based on the fluid transport equations. This theory predicts that the electrons of the plasma are attaining a temperature of about 15 eV in that part of the system where the dc magnetic field is about 80 G. More importantly, it is able to predict the output pulse quite well under the conditions that the ambient nitrogen pressure and the electron number density are low. The theory appears to fail as these parameters are increased.