Fig. 4.28.3. The electron velocity distribution fe (vx). The red (1), green (2), and blue (3) lines show fe (vx) at apet = 0, apet = 200 without Bc, and at apet = 200 with Bc for mcelape = 2, respectively. The electrons velocity vx is normalized by the velocity of light. According to Saito et al. (2003).
From Fig. 4.28.3 it follows that with the condition mcejct)pe = 2, the electrostatic field can more effectively accelerate the electrons in the x-direction than the electromagnetic wave driven by the instability without the background magnetic field. In this condition the maximum Lorentz gamma factor of electrons is about 3, and the number of accelerated particles that exceeds 0.9c is about two hundreds times as the number of accelerated particles in the condition without background magnetic field.
Saito et al. (2003) came to conclusion that:
1. The background magnetic field restrains the generation of the electromagnetic wave driven by this instability, and consequently it generates the electrostatic wave that has the wave vector parallel to the both magnetic field and the counter-streaming. This means that the nature of counter-streaming instability becomes electrostatic mode from electromagnetic mode.
2. This electrostatic field effectively accelerates the particles in the direction parallel to both the magnetic field and the counter-streaming.
3. The positron velocity distributions are the almost same as the electron velocity distributions.
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