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Streamers and pseudostreamers structure the corona at the largest scales, as seen in both eclipse and coronagraph white-light images. Their inverted-goblet appearance encloses broad coronal loops at the Sun and tapers to a narrow radial stalk away from the star. The streamer associated with the global solar dipole magnetic field is long-lived, predominantly contains a single arcade of nested loops within it, and separates opposite-polarity interplanetary magnetic fields with the heliospheric current sheet (HCS) anchored at its apex. Pseudostreamers, on the other hand, are transient, enclose double arcades of nested loops, and separate like-polarity fields with a dense plasma sheet. We use numerical magnetohydrodynamic simulations to calculate, for the first time, the formation of pseudostreamers in response to photospheric magnetic-field evolution. Convective transport of a minority-polarity flux concentration, initially positioned under one side of a streamer, through the streamer boundary into the adjacent preexisting coronal hole forms the pseudostreamer. Interchange magnetic reconnection at the overlying coronal null point(s) governs the development of the pseudostreamer above—and of a new satellite coronal hole behind—the moving minority polarity. The reconnection dynamics liberate coronal-loop plasma that can escape into the heliosphere along so-called separatrix-web ("S-Web") arcs, which reach far from the HCS and the solar equatorial plane, and can explain the origin of high-latitude slow solar wind. We describe the implications of our results for in situ and remote-sensing observations of the corona and heliosphere as obtained, most recently, by Parker Solar Probe and Solar Orbiter. [ABSTRACT FROM AUTHOR]

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]

Magnetically driven eruptions on the Sun, from stellar-scale coronal mass ejections to small-scale coronal X-ray and extreme-ultraviolet jets, have frequently been observed to involve the ejection of the highly stressed magnetic flux of a filament. Theoretically, these two phenomena have been thought to arise through very different mechanisms: coronal mass ejections from an ideal (non-dissipative) process, whereby the energy release does not require a change in the magnetic topology, as in the kink or torus instability; and coronal jets from a resistive process involving magnetic reconnection. However, it was recently concluded from new observations that all coronal jets are driven by filament ejection, just like large mass ejections. This suggests that the two phenomena have physically identical origin and hence that a single mechanism may be responsible, that is, either mass ejections arise from reconnection, or jets arise from an ideal instability. Here we report simulations of a coronal jet driven by filament ejection, whereby a region of highly sheared magnetic field near the solar surface becomes unstable and erupts. The results show that magnetic reconnection causes the energy release via 'magnetic breakout'-a positive-feedback mechanism between filament ejection and reconnection. We conclude that if coronal mass ejections and jets are indeed of physically identical origin (although on different spatial scales) then magnetic reconnection (rather than an ideal process) must also underlie mass ejections, and that magnetic breakout is a universal model for solar eruptions. [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]