Solar radio emissions: from simulations to laser experiment
Abstract
Solar flares generate intense electromagnetic radiation in the radio domain (1-100 MHz), part of which corresponds to emission at the electron plasma frequency ωp or its second harmonic 2ω_p. These waves are the signature of electron beams propagating in the interplanetary medium. Detected by space and ground-based radio telescopes, these electromagnetic waves can be used to remotely infer the characteristics of the electron beams. If the main steps of the process from electron beam to Electron Plasma Waves and mode conversion to electromagnetic radiations are known, several questions are still unresolved, in particular: (i) the efficiency of the conversion, (ii) the directionality of the process. To tackle these questions first PIC simulations, then laboratory laser-plasma experiment have been performed. If the parameters of the interplanetary plasma and laser-generated plasmas are very different in absolute values, they happen to be very similar in relative numbers (such as k⪉mbdaDe and T_e/T_i), which makes these laser experiments suitable for astrophysical purposes. The experiment was designed for the LULI 2000 facility (Ecole Polytechnique, France) operated at 2ω0 in the nanosecond regime. The results of PIC simulations and of the first experiment that hold in September 2018 will be presented.