Finding reconnection lines and flux rope axes via local coordinates in global ion-kinetic magnetospheric simulations

Magnetic reconnection is a crucially important process for energy transfer in plasma physics, the substorm cycle of Earth's magnetosphere and solar flares being prime examples. While 2D models have been widely applied to study reconnection, investigating reconnection in 3D is still in many aspects an open problem. Finding sites of magnetic reconnection in a 3D setting is not a trivial task, with several approaches from topological skeletons to Lorentz transformations proposed to tackle the issue. This work presents a complementary method by noting that the magnetic field structures near reconnection lines exhibit two-dimensional features that can be identified in a suitably chosen local coordinate system. We present applications of this method, with two approaches, to a hybrid-Vlasov Vlasiator simulation of the Earth's magnetosphere, showing the complex magnetic topologies created by reconnection. We also overview the dimensionalities of magnetic field structures in the simulation to support the use of such coordinate systems.