Current Sheet Formation in Force-Free Magnetic Fields
Abstract. The evolution of coronal magnetic fields in response to slow photospheric footpoint motions does not in general produce smooth a force-free eguilibrium. The presence of separatrix lines results in current sheet formation even under an infinitesimal shearing deformation of a 2-D magnetic field. When a separatrix without neutral points is present a regular perturbation approach is valid and preserves the magnetic field geometry. In the case of a neutral X-point perturbation the scheme fails and a geometry with cusped triple points is formed. In general these current sheets could create coronal heating, but when new flux emerges into a highly sheared field it could also trigger a solar flare.
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