Simulating the emission of electromagnetic waves in the terahertz range by relativistic electron beams

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Aims. We investigate the dynamics of relativistic electron beams propagating along a uniform magnetic field and the emission process of electromagnetic waves within the terahertz range from the solar photosphere. Our 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). Methods. We used a 2D3V fully relativistic electromagnetic particle-in-cell (PIC) simulation. Results. We did three different kinds of simulations. The first simulation confirmed that the growth rate of relativistic electron beam instability agrees well with the theoretical estimation. From the second simulation of the electron beam with finite width, we found that the beams are confined along the magnetic field and the electromagnetic waves are generated forward of the electron beams. Some fraction of the electrons are accelerated more than the initial beam velocity. From the third simulation where the electron beams propagate into the high density region, we found that strong electromagnetic waves are generated backward to the electron beams. We also found that the higher frequency emission like 405 GHz, which originate in the strong magnetic field region, becomes stronger than the 212 GHz emission, as shown in the observation by Kaufmann et al. (2004). These simulation results could be applied to the electromagnetic wave emission from the solar photosphere during the solar flares.