Astronomy and astrophysics

Magnetic Helicity in Astrophysics

by Simon Candelaresi (Nordita)

FA31 ()


Helical magnetic fields are ubiquitous in the universe. They arise naturally from the dynamo process observed in the Sun, galaxies and accretion discs. During the generation of magnetic fields in dynamos helicity reduces the formation of the field field which is particularly problematic in the astrophysical environment. How its presence and fluxes influence the astrophysical dynamo is part of this work, where it is show that fluxes can save the dynamo. The gauge dependence of magnetic helicity makes its physical significance questionable. Considering three gauges it is shown that time averaged fluxes, which are physically meaningful, are gauge-invariant. The topological interpretation of magnetic helicity as linkage and knotting rises questions about how the field's stability is connected to its topology. The dominance of magnetic helicity is confirmed, but we have signs that higher order topological invariants might play a role too.