title: Formation of current singularity in a topologically constrained plasma.
abstract: Recently a variational integrator for ideal magnetohydrodynamics in Lagrangian labeling has been developed. Its built-in frozen-in equation makes it optimal for studying current sheet formation. We use this scheme to study the Hahm-Kulsrud-Taylor problem, which considers the response of a 2D plasma magnetized by a sheared field under sinusoidal boundary forcing. We obtain an equilibrium solution that preserves the magnetic topology of the initial field exactly, with a fluid mapping that is non-differentiable. Unlike previous studies that examine the current density output, we identify a singular current sheet from the fluid mapping. These results are benchmarked with a constrained Grad-Shafranov solver. The same signature of current singularity can be found in other cases with more complex magnetic topologies.
authors.affiliation: Plasma Physics Laboratory and Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08543, USA.
authors.forename: Yao
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Plasma Physics Laboratory and Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08543, USA.
authors.forename: Yi-Min
authors.initials: YM
authors.lastname: Huang
authors.affiliation: Plasma Physics Laboratory and Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08543, USA.|Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Qin
authors.affiliation: Plasma Physics Laboratory and Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08543, USA.
authors.forename: A
authors.initials: A
authors.lastname: Bhattacharjee