Thursday

Comparative studies of fast and slow solar wind streams performed over the past decades have shown several differences between these solar wind regimes, which span from the large-scale structure to small-scale phenomena. This also includes the nature of the embedded turbulence, i.e. the Alfvénicity of the fluctuations. Indeed, large amplitude Alfvénic fluctuations are very common features in the solar wind while slow wind fluctuations have usually a smaller amplitude, are less Alfvénic and more variable.
Although the two-state classification of the solar wind primarily based on flow speed has been widely adopted, more in depth studies have found that even slow solar wind streams with a strong Alfvénic character have been identified and characterized, showing that in many ways they resemble fast solar wind. The similarities with the fast wind, including composition, suggest a similar solar origin. As a consequence, understanding the mechanism for the difference in speed may provide insights into the origin and acceleration of the solar wind in general.

This talk gives and overview on the slow Alfvénic wind, presenting observations performed at different heliocentric distances, from Wind at L1 to Helios, Solar Orbiter and Parker Solar Probe in the inner heliosphere, and it discusses how it fits in with the bigger picture of solar wind sources.