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SFB 591 » Projekte » A5
 

Title

Self-generated electromagnetic fields: Instabilities and energetic charged particle beams

Project manager

Prof. Dr. Reinhard Schlickeiser
Institut für Theoretische Physik IV
Weltraum- und Astrophysik
Ruhr-Universität Bochum

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  Summary
  Goals

A central question with the investigation of intensive cosmic radiation sources is the processing of free energy in the surrounding impact-poor, interstellar and intergalactic plasmas. To it all dynamic phenomena of the stellar development, i.e. all plasma reciprocal effects of phenomena like an explosion of stars (Novae, star hoist, Supernovae, Hypernovae) belong, dramatic events, like the fusion of neutron stars or black holes in binary systems, and the radiation generation in accredidated systems. Particularly with active galactic cores the enormous energy release is in these objects led back to the accretion of materia onto a supermassif black hole under formation of a accretion disc with perpendicular relativistic jet. These processes set enormous quantities of kinetic energy free in arranged streams, whose dissipation into the surrounding smooth interstellar and intergalactic plasmas leads to magnetized shock waves and two-current-instabilities that induce plasma heating and particle acceleration.

In this subproject the relaxation of particle beams is examined by kinetic instabilities of self-arranging plasma wave fields both analytically (on the basis of the quasi-linear description) and numerically. During the analytic investigations, in the case of propagating electron-proton-particle beams, the past restrictions are to be given up. This is done in regard to the wave propagation direction, its nature and to the frequency range of the waves and the postulat of cold plasmas. The numeric work aims to achieve the exact temporal development of the particle relaxation.

The work to the relativistic pick UP model is to be continued in particular for the relaxation of particle beams in self-activated plasma wave fields that are formed by kinetic instabilities. Here the restrictions in the case of outward propagating electron-proton-particle beams, regarding the wave propagation direction (not only parallel to the background magnetic field), the nature of the waves (not only parallel transversal Alfv�n waves but also electrostatic longitudinal waves in particular), and the frequency of the waves (not only Alfv�n waves but also the Whistler waves that are in particular important for electrons) are to be given up. In these calculations also the assumption of cold plasmas (temperature T = 0) is to be dropped and the influence both of a warm interstellar medium and a heating of the jet plasma is to be examined. The inclusion of the electrostatic instability with regard to the particle beam relaxation (Pohl, Lerche and Schlickeiser 2002) leads to the fact that half of the arranged jet energy is converted into electrostatic turbulence, which can heat up the jet material. In particular for the low-frequency emission the exact temperature balance from heater and refrigeration processes is crucial, since the temperature determines considerably the optical thickness of the jet medium. While as refrigeration process essentially only the thermal radiation of the jet plasma is available, the heating is caused by absorption of not-thermal radiation, the coulomb reciprocal effect of the high-energy particles as well as smooth dissipation of electrostatic turbulence. While thus the cooling depends only upon the temperature and the density of the jet material, the heating rate is a function of the density of the surrounding interstellar medium and therefor correlates with the high-energy radiation. One thus must expect short fluctuations of the temperature of the jet medium, which lead to brief fluctuations of the optical thickness. Therefore the low-frequency emission will show variability in the radio to optical frequency range, not only due to the fluctuations in the non-thermal particle spectrum, but also because of the fluctuations of the optical thickness. Possibly also a synchrotron-maser can operate.

A second large question is concerned with the nature of the outward propagating particle beams.

 
 
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