Abstract Details

Name: Pallavi Bhat
Affiliation: International Centre for Theoretical Sciences
Conference ID: ASI2021_280
Title : Magnetic field generation in closed and open domains
Authors and Co-Authors : Pallavi Bhat (International Centre for Theoretical Sciences), Steven Tobias (University of Leeds), Fausto Cattaneo (University of Chicago), Gianluigi Bodo (INAF Osservatorio Astronomico di Torino)
Abstract Type : Oral
Abstract Category : Stars, ISM and Galaxy
Abstract : The origin of large-scale magnetic fields in most astrophysical systems like the Sun, stars and galaxies remains a challenging open problem. Dynamo action in the underlying turbulent fluid is thought to be responsible for the emergence of coherent magnetic fields. Due to the enormity of magnetic Reynolds numbers in these astrophysical systems, current theoretical models of the turbulent dynamo struggle to generate large-scale field on fast dynamic timescales. The conservation properties of magnetic helicity can constrain the nonlinear evolution of the dynamo. We have performed direct numerical simulations of the turbulent dynamo to investigate if employing open boundaries relaxes the constraint imposed by magnetic helicity conservation. We find that in the open systems a net magnetic flux (or system-scale fields) of significant strength arises and provides a hint of alleviation of the magnetic Reynolds number dependence in the nonlinear evolution of the large-scale fields. A large part of the answer involves understanding the behaviour of the current helicity. We provide both an analytic and numerical look at how current helicity influences the evolution of the magnetic helicity.