Parker Solar Probe in the inner heliosphere: insights and problems

The solar magnetic field plays a dual role in the generation of the Heliosphere. On the one hand it creates the corona by storing and transmitting, via a Poynting flux crossing the photosphere and transition region, the energy provided by the dynamo and convective motions; on the other hand, it provides the confinement, or magnetic cage, through which the heated coronal plasma must break through - everywhere except solar polar regions around solar minimum - to produce the supersonic solar wind. Solar wind streams are characterized by different plasma properties, from overall speed, to temperature and temperature anisotropies, composition, as well as different properties for the embedded turbulence. While it has been established that the source of fast solar wind streams at solar minimum are the polar coronal holes, slower solar wind streams have contributions from different sources. The larger than expected filling factor of slow solar wind has been attributed to flows coming from coronal hole boundaries, i. e. , regions with large expansion factors, or from the complex mapping of the magnetic field from the photosphere into the heliosphere. The observation by Parker Solar Probe that much of the solar wind, independently of speed, is dominated by Alfvénic fluctuations, and the frequent observation of slow Alfvénic solar wind, previously observed relatively rarely in Helios and Wind data, provide evidence for a modified picture of solar wind origins. I will discuss the properties, origin and acceleration of different types of solar wind streams as observed by Parker Solar Probe in the inner heliosphere. Image credit: Jongsun Lee (Unsplash) (https: //unsplash. com/photos/moon-eclipse-F-pSZOⱼeE8).