Aceleração de elétrons devido à turbulência de Langmuir via simulação por partículas

Abstract

The presence of suprathermal particles has been continually detected in di erent regions of the interplanetary medium since the beginning of space exploration in the years 60s. In sito observations made by instruments aboard of the spacecraft and space satellites, show that the velocity distribution function of these particles have a more energetic tail, which di ers from the Maxwellian distribution functions, that are well described by kappa-like distribution functions. Kappa functions are used to t the observational data. However, the physical mechanisms responsible for the particle energization are still a topic in discussion in the literature. In this work we study the physical processes related to the acceleration of suprathermal electrons due to the instabilities caused in the interaction of a beam-plasma system, using a PIC particle simulation method (paticle-in-cell ). We simulate the interaction of a beam-plasma system with an electron beam with 1% and 4% of the background density. For both cases we observed the formation of suprathermal tails in the distribution function at the end of the interaction process. Comparing the results of the simulations with the theoretical description for this kind of system, we veri ed that the appearance of suprathermal particles in the distribution function occurs after the system reaches the turbulent phase (nonlinear wave-particle interaction), and analyzing the space-time evolution of the velocity distribution function of the beam and the background presented separately, we identify that the population of particles that makes up the suprathermal tail at the end of the simulation process is basically composed by the beam particles. Moreover, our results show that the velocity distribution function assumes a shape that is better adjusted by a kappa-like distribution function.