Enhanced near-complete absorption of electromagnetic waves by dual resonance in a magnetized plasma

There has been significant interest lately in the study of Electromagnetic (EM) waves interacting with magnetized plasmas. The variety of resonances and the existence of several pass and stop bands in the dispersion curve for different orientations of the magnetic field offer new mechanisms of EM wave energy absorption (PhysRevE.105.055209, Juneja_2023,vashistha2022localized,vashistha2020new). By an appropriate choice of inhomogeneous magnetic field, one can construct a configuration wherein the same EM wave pulse encounters more than one resonance in the plasma. A 2-D Particle - In - Cell (PIC) simulation using the OSIRIS4.0 platform has been carried out for the case of dual resonance. It is observed that in the presence of dual resonance, there is a significant enhancement in leading to almost complete absorption of laser energy by the plasma in certain cases. A detailed study of the influence of the relative location of the resonances, the effect of high input EM wave intensity, etc., has also been carried out.Comment: 11 pages, 10 figure

Harmonic generation in magnetized plasma for Electromagnetic wave propagating parallel to external magnetic field

The harmonic generation has always been of fundamental interest in studying the nonlinear nature of any physical system. In the present study, Particle - In - Cell (PIC) simulations have been carried out to explore the harmonic generation of Electromagnetic waves in a magnetized plasma. The EM wave propagation is chosen to be parallel to the applied external magnetic field. The simulations show the excitation of odd higher harmonics of RCP (Right circularly polarized) and LCP (Left circularly polarized) when the incident wave is linearly polarised. The harmonic generation is maximum when the incident EM wave frequency matches the electron cyclotron frequency. When the incident EM wave has a circular polarization, no harmonics get excited. A theoretical understanding of these observations has also been provided. The studies thus show that by appropriately tailoring of plasma parameters EM waves of higher frequencies and desired nature of circular polarization can be generated.Comment: 25 pages, 15 figure

Two dimensional effects of laser interacting with magnetized plasma

Recent advancements in low-frequency short-pulse $CO_2$ lasers and the production of strong magnetic fields have made experimental studies on laser interactions with magnetized plasma a near-future possibility. Therefore, theoretical and numerical simulation studies have been pursued lately in this direction [A. Das, Review of Modern Plasma Physics 4, 1 (2020)] illustrating a host of novel phenomena related to laser energy absorption [Vashistha et al., New Journal of Physics, 22(6):063023 (2020); Goswami et al., Plasma Physics and Controlled Fusion 63, 115003 (2021)], harmonic generation [Maity et al., Journal of Plasma Physics, 87(5) (2021)], etc. However, most of these studies have been carried out in one-dimensional geometry with the laser having infinite transverse extent, and the plasma target was considered cold. This manuscript explores the manifestation of the 2-D and thermal effects on the problem of a laser interacting with magnetized plasma. As expected, additional transverse ponderomotive force is shown to be operative. A finite temperature of the target, along with transverse density stratification generates, leads to diamagnetic drift for the two plasma species. The imbalance of this drift between the two species can be an additional effect leading to an enhancement of laser energy absorption. The Particle - In - Cell (PIC) simulations with the OSIRIS4.0 platform is used to explore these features.Comment: 15 pages, 12 figures, 12 equation

Ion heating in Laser interacting with magnetized plasma

The ion heating mechanism in the context of laser interacting with plasma immersed in a strong magnetic field is studied. The magnetic field is chosen to be strong for laser electromagnetic field propagation inside the plasma to be governed by the magnetized dispersion relation. Both X and RL mode configurations have been studied in detail using Particle - In - Cell (PIC) simulations. It is shown that the energy absorption process is governed by a resonant mechanism wherein the laser frequency matches with an underlying mode in the plasma. For X and RL mode configurations, these correspond to lower hybrid and ion cyclotron resonance, respectively. The absorption, however, is found to be most efficient at frequencies close to but not exactly matching with the resonance frequency. An understanding of the same has been provided. The role of laser polarization has been studied in detail.Comment: 21 pages, 17 figure

Controlling intense, ultrashort, laser-driven relativistic mega-ampere electron fluxes by a modest, static magnetic field

The guiding and control of ultrahigh flux, femtosecond relativistic electron pulses through solid density matter is of great importance for many areas of high energy density science. Efforts so far include the use of magnetic fields generated by the propagation of the electron pulse itself or the application of hundreds of Tesla magnitudes, pulsed external magnetic fields driven by either short pulse lasers or electrical pulses. Here we experimentally demonstrate the guiding of hundreds of keV mega-ampere electron pulses in a magnetized neodymium solid that has a very modest, easily available static field of 0.1 tesla. The electron pulses driven by an ultrahigh intensity, 30 femtosecond laser are shown to propagate beam-like, a distance as large as 5 mm in a high Z target (neodymium), their collimation improved and flux density enhanced nearly by a factor of 3. Particle-in-cell simulations in the appropriate parameter regime match the experimental observations. In addition, the simulations predict the occurrence of a novel, near-monochromatic feature towards the high energy end of the electron energy spectrum, which is tunable by the applied magnetic field strength. These results may prove valuable for fast electron beam-driven radiation sources, fast ignition of laser fusion, and laboratory astrophysics.Comment: 10 pages, 5 figure