Abstract
Type-III-burst radio signals can be mimicked in the laboratory via laser-plasma interaction. Instead of an electron beam generating Langmuir waves (LWs) in the interplanetary medium, the LWs are created by a laser interacting with a millimeter-sized plasma through the stimulated Raman instability. In both cases, the LWs feed the Langmuir decay instability which scatters them in several directions. The resulting LWs may couple to form electromagnetic emission at twice the plasma frequency, which has been detected in the interplanetary medium, and recently in a laboratory laser experiment [Marquès et al., Phys. Rev. Lett. 124, 135001 (2020)]. This article presents the first numerical analysis of this laser configuration using particle-in-cell simulations, providing details on the wave spectra that are too difficult to measure in experiments. The role of some parameters is addressed, with a focus on laser intensity, in order to illustrate the behavior of the electromagnetic emission's angular distribution and polarization.
Highlights
Electron beams from solar eruptions or interplanetary shocks produce intense radio emissions[1,2] at the plasma frequency ωp and its harmonic 2ωp
PIC numerical simulations have proven succesful in describing the physical scenario for the growth and coupling of waves that generate 2ωp emission in a laser-plasma experiment
The rich structure of this setup can have many outcomes, but we identified two main routes which result in different angular distributions and degrees of polarization
Summary
Electron beams from solar eruptions or interplanetary shocks produce intense radio emissions[1,2] at the plasma frequency ωp and its harmonic 2ωp. Following the original idea of Ginzburg & Zhelezniakov[3], the beams provide the free energy for the bump-on-tail instability which generates Langmuir waves (LW) The decay of these plasma waves leads to the emission of the electromagnetic waves. The present article explores this laser setup via largescale numerical particle-in-cell (PIC) simulations They allow to perform parametric studies and provide direct information on electrostatic waves that was not accessible in the experiment. These simulations support that the LDI-based scenario is dominant in these conditions, with conversion efficiencies and polarization coherent with the experimental results of Ref. 12.
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