Electrostatic Decay of Beam‐generated Plasma Turbulence

The study of the evolution of a suprathermal electron beam traveling througha background plasma is relevant for the physics of solar flares and theirassociated type III solar radio bursts. As they evolve guided by the coronalmagnetic field-lines, these beams generate Langmuir turbulence. Thebeam-generated turbulence is in turn responsible for the emission of radiophotons at the second harmonic of the local plasma frequency, which areobserved during type III solar radio bursts. To generate the radio emission,the beam-aligned Langmuir waves must coalesce, and therefore a process capableof re-directioning the turbulence in an effective fashion is required. Different theoretical models identify the electrostatic (ES) decay process L1-> L2 + S (L: Langmuir wave; S: Ion-acoustic wave) as the re-directioningmechanism for the L waves. Two different regimes have been proposed to play akey role: the back-scattering and the diffusive (small angle) scattering. Thispaper is a comparative analysis of the decay rate of the ES decay for eachregime, and of the different observable characteristics that are expected forthe resulting ion-acoustic waves.Comment: 14 pages, 8 Figures. AAS LaTeX Macros v5.0. To appear in The Astrophysical Journa