Magnetic field amplification in accretion discs - the disc dynamo

The turbulent dynamo is the most efficient process for amplifying magnetic fields in the present and early Universe. The growth of the magnetic field is exponential, which leads to dynamically significant magnetic energies on very short time scales. Dynamo action ranges from the Earth and the Sun, over the interstellar medium to galaxies and might have played an important role during the formation of the first stars in the Universe.

Despite its importance, our theoretical understanding of the dynamo process is limited. The basic mechanism is to convert turbulent, kinetic energy into magnetic energy by twisting, stretching and folding the field lines. This has been investigated with computer simulations in very artificial geometries, for example in periodic boxes. Here, we will test more realistic geometries, such as accretion discs around new-born stars. Questions to be answered include: "Can the field grow exponentially in a rotating, turbulent disc and what are the achieved exponential growth rates? What is the saturation level of the magnetic field when the back-reaction of the field starts to resist the tangling induced by turbulence? Is a dynamo-amplified field sufficient to launch a jet from the accretion disc?“ and finally, "How might this all affect star and planet formation?"

To answer these questions, we will use the FLASH code with our own existing modifications to form discs and drive turbulence. The project does not require any special skills, except some basic programming experience with Fortran/C type languages.

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