Pseudostreamers: Formation, Magnetic Topology and Plasma Properties

Abstract:

A traditional view of the origins of the solar wind states that slow wind streams arise from coronal hole boundaries due to the larger expansion factor. It is hard in this explanation to understand why the slow wind occupies so much space in the heliosphere. Pseudostreamers are multipolar features which develop into fields that are unipolar at greater heights. There is debate as to the speed and nature of the wind from pseudostreamers: it could be fast, slow, or in between. And, in general, they might form a network of slow wind which may or may not connect in the heliosphere to slow wind coming from around the heliospheric current sheet. Here we discuss the relationship between the expansion factor along PFSS extrapolated magnetic field lines of pseudostreamers and wind speed and plasma properties calculated with numeral modeling. We demonstrate how the resulting wind type depends on the stage of pseudostreamer development in the context of the global coronal environment: factors in determining wind speed include the height of the pseudostreamer null point, the presence or absence of filament channels, and the expansion of coronal magnetic field lines in the neighborhood of the pseudostreamer spine. This study helps to better understand the sources of slow and fast solar wind for the Solar Probe Plus mission.