Scene Setting Talk 1 – Spiro Antiochos “Slow Wind” Properties

1. Session: Connecting Slow Wind Theories to Current and Future Observationsby Justin Edmondson, Ben Lynch, AleidaHigginson, Xudong Sun and Liang Zhao Scene Setting Talk 1 – Spiro Antiochos • “Slow Wind” Properties • Compositional resembles the closed-field corona • slower speeds(but this is not the defining feature) • Strong variation in speed and especially composition • Always surrounds the HCS but can have a spatial extent up to 30 degrees away from HCS   • Theories (Location! Location! Location!) • Expansion factor– the slow wind is coming from the open field lines at the edges of coronal holes (this is steady state!) • S-Web – the slow wind is coming from closed field lines which interchange at the edges of coronal holes (this is dynamic!) • Interchange reconnection everywhere: the slow wind is coming from closed field lines which interchange throughout the closed field corona (this is dynamic!)

2. Connecting Slow Wind Theories to Current and Future Observations Scene Setting Talk 2 – Joe Borovsky • At both helmet streamer and pseudo streamer crossings • The transition from slow to fast wind there is an extremely sharp boundary between the speeds, proton entropy, and charge-state ratios, which all occur within a few minutes of each other • The transition from fast to slow wind shows a much more gradual boundary, as expected in the rarefaction region BUT the alignment between the speed, charge-state, and entropy transition is much farther apart than you would expect from just rarefaction effects (10-15 hours). Slides Show: Yuan-KuenKo • Low velocity fluctuations dip is a good marker to distinguish the slow wind from the fast wind, nearly all solar wind parameters (IMF, proton, electron, and heavy ions) line up within this low velocity fluctuation interval via super-epoch analysis. Happens near both heliosphericcurrent sheet crossing or pseudostreamer crossings and have nearly identical properties.

3. Connecting Slow Wind Theories to Current and Future Observations • From the discussion, we determined the following specific questions for the upcoming missions. • Remote sensing • Do the elemental abundances observed by Solar Orbiter (SO) and Parker Solar Probe (PSP) change as a function of position across a coronal hole? • How does the plasma variability measured by SO and PSP change as a function of angle from the center of the streamer stalk? Can we measure the boundary between the expansion factor “Slow Wind 1”, and plasma sheet “Slow Wind 2”. • How do coronal hole boundaries measured by SO change over time? On what time scales? • Can you see an S-Web arc with heliospheric imagers? What are the signatures? • In situ • Measure wind in S-Web arc and compare with predictions of quasi-steady models. • How does the magnetic field variability measured by SO and PSP change as a function of angle from the HCS? Especially inside 20 RS. Look for Slow 1 – Slow 2 boundary. • Work closely with modelers to calculate signatures of interchange reconnection and test predictions along S-Web arcs.

4. Need modelers to make specific predictions for observable signatures that address the previous questions. • Dedicated SHINE Campaign!! In order to answer these questions with PSP and SO, we need a coordinated effort to determine the connection of the magnetic field and the plasma back to the photosphere!

5. Theories for Slow Wind Origins • Expansion factor: • Open field near coronal hole boundary; due to same quasi-steady process as fast wind • Dynamic S-Web: • Closed field near coronal hole boundary; due to dynamics • Interchange: • Throughout closed field region; due to dynamics Open-closed structure critical to all models – never simple dipole

6. Helmet-Streamer Crossing Crooker et al. 2014 ? ♯

7. Pseudostreamer Crossing Crooker et al. 2014 ? ♯