Interpreting magnetic helicity flux in solar flux emergence. (arXiv:1902.07997v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Prior_C/0/1/0/all/0/1">Chris Prior</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+MacTaggart_D/0/1/0/all/0/1">David MacTaggart</a>
Magnetic helicity flux gives information about the topology of a magnetic
field passing through a boundary. In solar physics applications, this boundary
is the photosphere and magnetic helicity flux has become an important quantity
in analysing magnetic fields emerging into the solar atmosphere. In this work
we investigate the evolution of magnetic helicity flux in magnetohydrodynamic
(MHD) simulations of solar flux emergence. We consider emerging magnetic fields
with different topologies and investigate how the magnetic helicity flux
patterns corresponds to the dynamics of emergence. To investigate how the
helicity input is connected to the emergence process, we consider two forms of
the helicity flux. The first is the standard form giving topological
information weighted by magnetic flux. The second form represents the net
winding and can be interpreted as the standard helicity flux less the magnetic
flux. Both quantities provide important and distinct information about the
structure of the emerging field and these quantities differ significantly for
mixed sign helicity fields. A novel aspect of this study is that we account for
the varying morphology of the photosphere due to the motion of the dense plasma
lifted into the chromosphere. Our results will prove useful for the
interpretation of magnetic helicity flux maps in solar observations.
Magnetic helicity flux gives information about the topology of a magnetic
field passing through a boundary. In solar physics applications, this boundary
is the photosphere and magnetic helicity flux has become an important quantity
in analysing magnetic fields emerging into the solar atmosphere. In this work
we investigate the evolution of magnetic helicity flux in magnetohydrodynamic
(MHD) simulations of solar flux emergence. We consider emerging magnetic fields
with different topologies and investigate how the magnetic helicity flux
patterns corresponds to the dynamics of emergence. To investigate how the
helicity input is connected to the emergence process, we consider two forms of
the helicity flux. The first is the standard form giving topological
information weighted by magnetic flux. The second form represents the net
winding and can be interpreted as the standard helicity flux less the magnetic
flux. Both quantities provide important and distinct information about the
structure of the emerging field and these quantities differ significantly for
mixed sign helicity fields. A novel aspect of this study is that we account for
the varying morphology of the photosphere due to the motion of the dense plasma
lifted into the chromosphere. Our results will prove useful for the
interpretation of magnetic helicity flux maps in solar observations.
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