Electron heating in bulk overdense plasma aided by time dependent external magnetic field

Abstract: This study investigates the localized electron heating in a bulk overdense plasma. The method relies on using a time dependent magnetic field. An initially high external magnetic field imposed on the overdense plasma target enables the propagation of a laser pulse inside it through the pass bands that occur in the magnetized dispersion relation. The choice of decaying external magnetic field is then tailored appropriately to achieve Electron Cyclotron Resonance (ECR) with the frequency of the laser electromagnetic field. At the resonance location, the field energy of the laser gets transferred to the electrons. These studies have been carried out with the help of the Particle-In-Cell (PIC) simulation technique on the OSIRIS4.0 platform. A detailed study has been carried out to illustrate the energy gain by electrons for a variety of temporal profiles of the magnetic field, laser intensities, and polarizations. The experiments in this regime may be within reach in the near future. For instance, the choice of long-wavelength CO$_2$ laser requires a magnetic field of about 10s of kilo Tesla to comfortably elicit a magnetized response from electrons. Recent technological advancements have shown the generation of about 1.4 kilo Tesla of magnetic field.