Berlin 2014 – wissenschaftliches Programm

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SYPA: Symposium Plasma-Astrophysik

SYPA 1: Plasma Astrophysics

SYPA 1.4: Hauptvortrag

Donnerstag, 20. März 2014, 15:30–16:00, SPA Kapelle

Turbulent dynamo effects in astrophysical plasmas — •Wolfram Schmidt and Dominik Schleicher — Institut für Astrophysik, Göttingen

I will discuss how magnetic fields in astrophysical plasmas, particularly on cosmological scales, are amplified by turbulent dynamo effects. In numerical simulations of cosmological structure formation, two different amplification mechanisms are found. Primarily, the compression of the plasma due to gravity and shocks resulting from the accretion onto massive halos enhances magnetic fields. In addition, the fields are amplified by the shear of turbulent flows, which can be interpreted as turbulent dynamo. Both mechanisms yield significant contributions to the generation of strong and nearly saturated magnetic fields from very week seed fields. In numerical simulations, however, it is generally not possible to fully resolve turbulence. Moreover, the dissipation of magnetic energy by reconnection occurs on small scales below the resolution limit and is usually treated by numerical dissipation. The problem is further complicated by collisionless plasmas, such as the hot baryonic gas in galaxy clusters, in which the physical dissipation mechanism is not yet well understood. These issues can be addressed by novel subgrid scale models that incorporate magnetic field amplification by numerically unresolved turbulence as well as dissipative effects in the collisionless, kinetic regime. I will report on recent advances in this direction.