School of Astronomy (SoA) - Weekly Seminar

Streaming Cosmic Ray Driven Instabilities

I first review some of the most important roles of Cosmic Rays (CRs) in the astronomical systems from protoplanetary discs to the cluster of galaxies. In addition to the ionization and the heating of CRs, they may have a significant dynamical role. Also, just recently it has been proposed that amplification of the magnetic field under certain circumstances is mainly due to the streaming instability by CRs. Then, I mainly concentrate on this aspect of CRs by illustrating streaming CRs driven instabilities for both the non-magnetized and the magnetized CRs. However, it is shown that the cosmic ray back-reaction results in the streaming instability having considerably larger growth rates than that due to the return current of the background plasma. This increase is by a factor of the square root of the ratio of the background plasma mass density to the cosmic ray mass density. Possible astrophysical implications are discussed along with emphasizing on the directions for the future work in the field

IPM Larak Building, School of Astronomy