| Abstract: Magnetic topology governs the storage and release of energy in the solar corona. Changes in topology imply magnetic reconnection, a process that converts magnetic energy into heat and kinetic energy and drives solar transients such as flares, coronal jets. In three dimensions, reconnection is associated with topological structures including magnetic null points and separators. Although 3D nulls are found to be abundant in the solar atmosphere, the physical mechanisms responsible for their generation remain poorly understood.
This thesis investigates the spontaneous creation and annihilation of 3D magnetic nulls using Implicit Large Eddy Simulations of incompressible magnetohydrodynamics without explicit magnetic diffusivity. All simulations rigorously preserve null identities and conserve the net topological degree. Three complementary scenarios are examined. First, an imposed flow acting on a magnetic configuration containing a single proper radial null triggers magnetic reconnection and produces null pairs with opposite topological degrees. These nulls form away from the original null via a mechanism distinct from classical pitchfork bifurcation, and additional null pairs emerge spontaneously during the evolution. Second, a data-driven simulation of a flaring solar active region, initialized using Non-Force-Free Field extrapolations of observed vector magnetograms, reveals spontaneous null generation through reconnection. The newly formed nulls exhibit dome-shaped fan structures and are associated with chromospheric brightenings consistent with slip reconnection, before undergoing pairwise annihilation. Third, simulations starting from chaotic magnetic fields with no pre-existing nulls demonstrate that increasing magnetic chaoticity leads to earlier and more frequent null formation, including evolving spiral and radial nulls that ultimately annihilate through reconnection.
Across all cases, magnetic reconnection is identified as the fundamental driver of null generation and annihilation. These results support a reconnection-assisted mechanism for the spontaneous formation of 3D nulls, offering a compelling explanation for their ubiquity in the solar atmosphere and their potential contribution to coronal heating.
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