On the Origin of the Slow Solar Wind: Periodic Plasma Release from Pseudostreamers

We present observations of quasi-periodic release of plasma from pseudostreamers, and demonstrate that these observations place severe constraints on the origin of both the slow solar wind and pseudostreamer dynamics. Though quasi-periodic release of slow solar wind plasma is routinely observed in remote white light images, such plasma release is often associated with the tips of helmet streamers and the heliospheric current sheet. Helmet streamers and the heliospheric current sheet are natural locations for magnetic reconnection to occur, both in the form of complete disconnections and interchange reconnection. However, pseudostreamers are not associated with the heliospheric current sheet, and are predicted by some models to have steady solar wind release. In contrast, in the S-web model of solar wind formation, pseudostreamers and their magnetic extensions into the heliosphere are also locations where slow solar wind is released sporadically through magnetic reconnection. We present the first observations demonstrating that quasi-periodic plasma release occurs in pseudostreamers as well. We build a comprehensive picture of the dynamics by combining remote-sensing data with in situ composition and magnetic connectivity information. Our results have critical implications for the magnetic topology of pseudostreamers and for their reconnection dynamics. This analysis pushes the limits of current instrument resolution and sensitivity, showing the enormous potential science to be accomplished with Solar Probe Plus and Solar Orbiter.