Investigating Alfvenic wave propagation in coronal open-field regions

The physical mechanisms behind accelerating solar and stellar winds are a long-standing astrophysical mystery, although recent breakthroughs have come from models invoking the turbulent dissipation of Alfven waves. The existence of Alfven waves far from the Sun has been known since the 1970s, and recently the presence of ubiquitous Alfvenic waves throughout the solar atmosphere has been confirmed. However, the presence of atmospheric Alfvenic waves does not, alone, provide sufficient support for wave-based models; the existence of counter-propagating Alfvenic waves is crucial for the development of turbulence. Here, we demonstrate that counter-propagating Alfvenic waves exist in open coronal magnetic fields and reveal key observational insights into the details of their generation, reflection in the upper atmosphere and outward propagation into the solar wind. The results enhance our knowledge of Alfvenic wave propagation in the solar atmosphere, providing support and constraints for some of the recent Alfven wave turbulence models.