Author: Joshua P. Sauppe
Requested Type: Poster
Submitted: 2016-02-15 21:33:16
Co-authors: W. Daughton
Los Alamos National Laboratory
Los Alamos, NM 87544
Magnetic reconnection is the process by which magnetic field lines break and reconnect, releasing magnetic energy and altering the magnetic topology. It has been extensively studied in two-dimensional systems, where reconnection occurs at well defined positions known as X-points defined by the vanishing of the in-plane components of magnetic field. However, this process is much more complicated in three dimensions where there are no clear locations at which reconnection occurs. Theoretical work [Priest 1995] has suggested that reconnection occurs at quasi-separatrix layers (QSLs), regions where the magnetic field line connectivity changes drastically. This has recently been investigated experimentally on the large plasma research device (LAPD) through the interaction and merging of two distinct magnetic flux ropes [Gekelman 2016]. Measurements confirm that the quasi-potential, a measurement of the nonlinear reconnection rate [Hesse 2005], is
indeed large near these QSLs, supporting the earlier theoretical predictions.
We present initial results of the investigation of 3D magnetic reconnection of two neighboring flux ropes in parameter regimes comparable to the setup on LAPD, using both particle-in-cell computations with VPIC and fluid computations with NIMROD. We focus on the 3D behavior of the Fadeev equilibrium [Fadeev 1965], which consists of two neighboring magnetic islands in a periodic domain. This equilibrium has been well-studied in 2D, where the islands merge as a result of the island coalescence instability. For parameters relevant to LAPD, the initial separation of the island centers is comparable to the ion skin depth, and we find that two-fluid effects substantially impact the details of the merging event. The reconnection behavior is examined as a function of both the guide field strength and the parallel wavenumber.