On the Spontaneous Generation of Three-dimensional Magnetic Nulls

Three-dimensional magnetic nulls relate to magnetic topology, and are propitious for triggering solar coronal transients. Although abundant in nature, their generation is not established. This paper reports magnetohydrodynamic simulations indicating the nulls to be dissipative self-organized structures. Categorically, the results of two case studies are presented. First, a potential null located at the origin of a Cartesian coordinate system is subjected to a sinusoidal flow. The null is seen to bifurcate while conserving the net topological degree. Using the corresponding deformed magnetic field as an initial condition, the magnetofluid is subsequently evolved by dissipating its magnetic and kinetic energies through magnetic reconnection and viscous dissipation. In effect, a current-carrying null develops in the process. Second, another simulation is initiated with a modified Arnold-Beltrami-Childress (ABC) magnetic field which exerts a Lorentz force on the magnetofluid and has no nulls within the computational volume. Astoundingly, allowed the magnetofluid to relax, nulls having mixed topological degrees are generated. The modified ABC field being chaotic, the spontaneous appearance of nulls establishes emergence of ordered magnetic structures from chaos-a trait of self-organized structures-explaining their ubiquity in naturally existing plasmas.