Magnetic topology dynamics during reconnection events in RFX-mod

Magnetic reconnection is a self-organized phenomenon of redistribution of currents in a plasma, which changes dramatically the topology of the magnetic field. It is found in disparate environments, such as the magnetosphere, the solar corona and, last but not least, toroidally confined plasmas for nuclear fusion research. The study of reconnection in a laboratory is of paramount importance for comparison with space plasmas, where measurements are more difficult to perform, and also of practical importance, since reconnection sustains the magnetic field but is also responsible for fast particle losses, causing plasma–wall interaction (PWI) and deterioration of confinement. This paper is devoted to the study of particle orbits during a reconnection event in the reversed-field experiment-modified device. The PWI patterns are measured via a fast camera looking at the graphite-covered inner wall, and compared with detailed simulations of particle motion in the 3D magnetic topology, performed with the Hamiltonian, guiding center ORBIT. The inclusion of an electrostatic potential is shown to be a fundamental ingredient for explaining some typical features of reconnection in the laboratory, such as particle trapping in the potential, which are also seen in other environments, namely the solar corona and Earth’s magnetosphere.