Influência da Distribuição de Partículas do Vento Solar na Instabilidade de Ondas em Plasmas

Abstract

We simulate the interplanetary environment, from a background plasma (ambient) de scribed by a Kappa Velocity Distribution Function (VDF-κ). This environment plasma interacts with counterstreaming beams that are emitted by the Sun. These beams are de scribed by a Maxwellian Distribution Function (VDF-Maxwellian) and this beam-plasma interaction causes the growth of waves in the plasma (dispersive modes). In this work, we employ the Langmuir modes, since they are related to type III solar emissions. Type III emissions are the result of instabilities produced by beams of particles that can be gen erated in eruptive solar events, such as flares and Coronal Mass Ejections (CME’s). The VDF-κ was chosen to represent the background plasma in order to verify the influence on the wave growth from the variation of the κ spectral index. First, we carried out a study about VDF-κ and justified the reason for its use to represent the plasma environment. We used as the basis of the study the quasilinear theory because, it allows to study the evolution of plasma after an initial disturbance. To study the influence of the κ-index, we varied some parameters such as density and velocity of the beams. With this, it is possible to verify the wave growth behavior from this variation. The results were obtained in two different ways, by numerical and analytical. From this it was possible to find values for wave energy, magnification factor and initial growth rate. From comparison, a situation in which the ambient plasma was described by an VDF-Maxwellian was also simulated. The results showed that in addition to the influence of the κ-index the variation of the velocity and density of the beams affect the direct wave growth. In particular, for environments with the same characteristics, the VDF-κ case presented a smaller wave growth, when compared to an VDF-Maxwellian.