Plasma and magnetic field dynamics in the young solar wind

Abstract

<p>Parker Solar Probe (PSP) has completed four encounters with the Sun since launch, three with a perihelion of 35.7 solar radii and one at 27.9 solar radii in January of this year.  More than a factor of two closer to the Sun than any previous mission, observations by the spacecraft are already revealing a surprisingly dynamic and non-thermal solar wind plasma near the Sun.  An overview of initial findings related to the solar wind and coronal plasmas will be presented, including the discovery of large-amplitude velocity spikes, highly non-thermal distribution functions, and large non-radial flows of plasma near the Sun observed by the Solar Wind Electrons Alphas and Protons (SWEAP) Investigation plasma instruments and the FIELDS Investigation electromagnetic field instruments.  Once PSP dropped below a quarter of the distance from the Sun to the Earth, SWEAP began to detect a persistent and growing rotational circulation of the plasma around the Sun peaking at 40-50 km/s at perihelion as the Alfvén mach number fell to 3.  This finding may support theories for enhanced stellar angular momentum loss due to rigid coronal rotation, but the circulation is large, and angular momentum does not appear to be conserved, suggesting that torques still act on the young wind at these distances.  PSP also measured numerous intense and organized Alfvénic velocity spikes with strong propagating field reversals and large jumps in speed.  These field reversals and jets call for an overhaul in our understanding of the turbulent fluctuations that may, by energizing the solar wind, hold the key to its origin.</p>