Nordita Astrophysics seminars

Decay of helical and non-helical magnetic knots

by Simon Candelaresi (Nordita)

122:026 ()


We present calculations of the relaxation of magnetic field structures that have the shape of particular knots and links. A set of helical magnetic flux configurations is considered, which we call $n$-foil knots of which the trefoil knot is the most primitive member.

We also consider two non-helical knots, namely the Borromean rings as well as a single interlocked flux rope that also serves as the logo of the Inter-University Centre for Astronomy and Astrophysics in Pune, India. The field decay characteristics of both configurations is investigated and compared with previous calculations of helical and non-helical triple ring configurations. For the n-foil knots the decay is described by power laws that range form t^{-2/3} to t^{-1/3}, which can be as slow as the t^{-1/3} behavior for helical triple-ring structures that was seen in earlier work. The two non-helical configurations decay like t^{-1}, which is somewhat slower than the previously obtained t^{-3/2} behavior in the decay of interlocked rings with zero magnetic helicity. We attribute the difference to the creation of local structures that contain magnetic helicity which inhibits the field decay due to the existence of a lower bound imposed by the realizability condition. We speculate that higher order topological invariants beyond magnetic helicity may also be responsible for slowing down the decay of the two more complicated non-helical structures mentioned above.


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