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Coronal jets are observed above minority-polarity intrusions throughout the solar corona. Some of the most energetic ones occur on the periphery of active regions where the magnetic field is strongly inclined. These jets exhibit a non-radial propagation in the low corona as they follow the inclined field, and often have a broad, helical shape. We present a three-dimensional magnetohydrodynamic simulation of such an active-region-periphery helical jet. We consider an initially potential field with a bipolar flux distribution embedded in a highly inclined magnetic field, representative of the field nearby an active region. The flux of the minority polarity sits below a bald-patch separatrix initially. Surface motions are used to inject free energy into the closed field beneath the separatrix, forming a sigmoidal flux rope that eventually erupts producing a helical jet. We find that a null point replaces the bald patch early in the evolution and that the eruption results from a combination of magnetic breakout and an ideal kinking of the erupting flux rope. We discuss how the two mechanisms are coupled, and compare our results with previous simulations of coronal-hole jets. This comparison supports the hypothesis that the generic mechanism for all coronal jets is a coupling between breakout reconnection and an ideal instability. We further show that our results are in good qualitative and quantitative agreement with observations of active-region-periphery jets. [ABSTRACT FROM AUTHOR]

Magnetic reconnection in three dimensions (3D) is a natural extension from X-point reconnection in two dimensions. Of central importance in the 3D process is a localized non-ideal region within which the plasma and magnetic field decouple allowing for field line connectivity change. In practice, localized current structures provide this localization; however, mathematically a similar effect can be achieved with the localization of plasma resistivity instead. Physically though, such approaches are unrealistic, as anomalous resistivity requires very localized currents. Therefore, we wish to know how much information is lost in localizing η instead of current? In this work we develop kinematic models for torsional spine and fan reconnection using both localized η and localized current and compare the non-ideal flows predicted by each. We find that the flow characteristics are dictated almost exclusively by the form taken for the current profile with η acting only to scale the flow. We do, however, note that the reconnection mechanism is the same in each case. Therefore, from an understanding point of view, localized η models are still important first steps into exploring the role of non-ideal effects. [ABSTRACT FROM PUBLISHER]