Amplification of electromagnetic radiation by a nonequilibrium plasma unstable against the development of Weibel instability

Collective modes of plasma formed by multiphoton ionization of rarefied gas

“…In particular, the study of the dispersion laws, for example, by registration of Raman scattering, opens up the possibility to obtain information on the evolution of the non-equilibrium distribution of photoelectrons. In turn, the presence of effectively developing instabilities allows us to count on additional opportunities for electromagnetic pulse amplification, similar to those revealed for the plasma formed during tunnel ionization of gas atoms (see, e.g., [30,33]). The excitation of the considered unstable modes during multiphoton ionization is due to plasma anisotropy caused by the presence of counter streams of photoelectrons along the strength vector of the linearly polarized ionizing field.…”

“…Thus, due to the anisotropy of particle energy or the presence of electron flows, energy is transferred to the electromagnetic field. Anisotropic non-equilibrium electron distribution evolves over time due to both pair collisions of particles [30] and because of the inverse influence of the instabilities on the initial state of plasma. According to [31], the inverse effect of the instability on the anisotropic distribution begins to affect when the energy density of the growing quasistationary magnetic field due to the instability reaches ten percent of the electron kinetic energy density.…”

“…A number of interesting predictions was also made for rarefied gases. There is a possibility of amplifying low-frequency radiation pulses in photoionized gas plasma [30,[33][34][35][36][37]. In addition, the longitudinal waves with a linear dispersion law corresponding to an electronic sound is possible in photoionized plasma [38,39].…”