Turbulence in the young solar wind - Parker Solar Probe observations and global modeling

NASA's Parker Solar Probe (PSP) mission was launched in 2018, with the primary science objective of determining the structure and dynamics of the Sun's coronal magnetic field, understanding how the solar corona and wind are heated and accelerated, and determining the processes that accelerate energetic particles. The spacecraft's pioneering observations in the near-Sun space environment have led to novel insights, and raised new questions, regarding the nature and role of turbulence in the young solar wind. One topic of deep relevance is the nature of the transition from the magnetically structured, sub-Alfvénic inner corona into the super-Alfvénic, increasingly hydrodynamic young solar wind. This talk will first present an overview of the PSP mission and highlight some of its discoveries. We will then cover recent work exploring the transition from sub-Alfvénic to super-Alfvénic flow, using global magnetohydrodynamic modeling with turbulence transport, together with in-situ observations. We explore the possibility that, due to the influence of broadband turbulence, the critical Alfvénic transition takes place in fragmented and disconnected subvolumes within a general Alfvén critical zone. This picture stands in contrast to the conventional view of an Alfvén surface that separates simply connected regions. PSP has recently obtained the first measurements of sub-Alfvénic solar wind near the Sun, and we will end the presentation with a statistical analysis of magnetic turbulence observed in these regions.