A&A 470, 1117-1122 (2007)
DOI: 10.1051/0004-6361:20066978

Emission of electromagnetic waves by proton beams propagating in nonuniform solar plasmas

J. I. Sakai and Y. Nagasugi

Laboratory for Plasma Astrophysics, Faculty of Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan
    e-mail: sakaijun@eng.u-toyama.ac.jp

(Received 20 December 2006 / Accepted 24 April 2007)

Abstract
Aims.We investigate the dynamics of proton beams propagating along a uniform magnetic field, as well as across the magnetic field in nonuniform solar plasmas, paying attention to the emission process of electromagnetic waves. The aim is to understand a new solar-burst component emitting only in the terahertz range during the solar flare observed by Kaufmann et al. (2004, ApJ, 603, L121).
Methods.We used a 2D3V, fully relativistic, electromagnetic particle-in-cell (PIC) simulation.
Results.From the simulation where the proton beams propagate along a uniform magnetic field into the high-density region, we found that strong electromagnetic waves are generated behind the proton beams. When the proton beams propagate perpendicular to the magnetic field, we found that the extra-ordinary mode can be excited from two electron Bernstein waves through three-wave interactions. These simulation results could be applied to the electromagnetic wave emission from the solar photosphere during the solar flares.

Key words: plasmas -- shock waves -- Sun: flares -- Sun: radio radiation -- acceleration of particles

© ESO 2007

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