Plasma astrophysics


    99% of cosmic matter is in the form of ionised plasma. In this form, a diverse range of interactive processes become operational on account of the magnetic fields that the motion of these particles are able to sustain. It is within such an environment that fast charged particles both originate and reside. Furthermore, the energies stored in the magnetic field, turbulences, and non-thermal particles (cosmic rays) are comparable in interstellar plasma, implying their close links among each other.
    For instance, if the kinetic energy in turbulences is larger than the magnetic energy, the magnetic field can be amplified by a turbulent dynamo; if the flux of cosmic rays is sufficiently high, they can also drive turbulences through streaming and other kinetic instabilities; on the other hand, turbulences accelerate particles directly through the stochastic process or facilitate their acceleration at shocks and at sites of magnetic reconnection.

    We explore the basic processes in large-scale plasma, which are closely linked to many astrophysical phenomena in environments ranging from our solar system to the early universe. This area of research has been among the most rapidly developing fields in theoretical astrophysics for the past two decades. A list of particular topics includes cosmic-ray propagation and acceleration, plasma instabilities, magnetohydrodynamic turbulences, cosmic magnetic fields, grain dynamics, etc.


    The movie shows simulation results for drifting cosmic rays: The top panel indicates the turbulent magnetic field and the bottom panel depicts the density of interstellar gas. Initially the interstellar gas is at rest and the cosmic rays drift to the left. After a while the structures in both the magnetic field and the gas density appear to drift as well.