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Articles

• Schober, J.; Schleicher, D. ; Klessen, R.:
  Magnetic Field Amplification in Young Galaxies
  (submitted to "Astronomy & Astrophysics")
• Schleicher, D.; Latif, M.; Schober, J.; Schmidt, W.; Bovino, S.; Federrath, C.; Niemeyer, J.; Banerjee, R.; Klessen, R.:
  Magnetic fields during high redshift structure formation
  (proceedings article for "Annual Meeting of the Astronomische Gesellschaft" 2012)
• Schober, J.; Schleicher, D. ; Klessen, R..; Federrath, C.; Bovino, S.; Glover, S.; Banerjee, R.:
  Small-Scale Dynamo Action in Primordial Halos
  (proceedings article for "28th General Assembly of the IAU" 2012)
• Schleicher, D.; Schober, J.; Federrath, C.; Bovino, S.; Schmidt, W.:
  The small-scale dynamo: Breaking universality at high Mach numbers
  ("New Journal of Physics" 2013)
• Bovino, S.; Schleicher, D.; Schober, J.:
  Turbulent magnetic field amplification from the smallest to the largest magnetic Prandtl numbers: Implications of the turbulent spectra
  ("New Journal of Physics" 2013)
• Schober, J.; Schleicher, D.; Bovino, S.; Klessen, R.:
  The Small-Scale Dynamo at Low Magnetic Prandtl Numbers
  ("Physical Review E" 2012)
• Schober, J.; Schleicher, D.; Federrath, C.; Glover, S.; Klessen, R.; Banerjee, R.:
  The Small-scale Dynamo and Non-ideal Magnetohydrodynamics in Primordial Star Formation
  ("Astrophysical Journal" 2012)
• Schober, J.; Schleicher, D.; Federrath, C.; Klessen, R.; Banerjee, R.:
  Magnetic field amplification by small-scale dynamo action: Dependence on turbulence models and Reynolds and Prandtl numbers
  ("Physical Review E" 2012)
• Schleicher, D.; Schober, J.; Federrath, C.; Miniati, F.; Banerjee, R.; Klessen, R.:
  Magnetic fields in the first galaxies: Dynamo amplification and limits from reionization
  (proceedings article for "Magnetic Fields in the Universe III: From Laboratory and Stars to Primordial Structures" 2011)
• Federrath, C.; Chabrier, G.; Schober, J.; Banerjee, R.; Klessen, R. S.; Schleicher, D.:
  Mach Number Dependence of Turbulent Magnetic Field Amplification: Solenoidal versus Compressive Flows
  ("Physical Review Letters" 2011)

Diploma Thesis

In this work we explore the small-scale dynamo - a mechanism which may rapidly amplify a week magnetic seed field by converting turbulent kinetic energy into magnetic energy. %The basics for the description of this process are magnetohydrodynamics and turbulence. Both of these theories are presented in this work as far as necessary and available. Moreover, we give an introduction to the theory of magnetohydrodynamical dynamos in general. The small-scale dynamo is described by a theory of Kazantsev, which depends crucially on the nature of turbulence. We propose a model for different types of turbulence and use the Kazantsev theory to determine properties of the small-scale dynamo. With our model we find that the critical magnetic Reynolds number, which needs to be exceeded for small-scale dynamo action, lies between 110 and 2700. Furthermore, we show that the growth rate of the small-scale magnetic field depends strongly on the hydrodynamical Reynolds number Re. In the limit of infinite magnetic Prandtl numbers the growth rate Γ scales between Γ∝Re^1/2 and Γ∝Re^1/3 for different types of turbulence. For decreasing magnetic Prandtl number, the growth rate of the small-scale dynamo decreases. We apply our model to the magnetic fields in the formation of the first stars. For this we estimate the typical quantities of primordial gas by using a one-zone chemistry code. The resulting small-scale magnetic field reaches its saturation value almost instantly and thus we expect it to be dynamically important in primordial star formation.

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