Space Physics Seminar fall-2019

Parker Solar Probe (PSP) launched on August 12th, 2018, its mission to carry out the first in situ exploration of the outer solar corona and inner Heliosphere. Observations of solar-wind plasma at a distance of ~ 36 RS, well inside the radius at which stream interactions become important, have shown that Alfvén waves organize into structured velocity spikes up to minutes long that are associated with propagating S-like bends in the magnetic-field lines. These are associated with measured magnetic field patches of large, intermittent reversals with enhanced Poynting flux interspersed with a smoother and less turbulent flow with a near-radial magnetic field. This slow, Alfvénic solar wind emerged from a small, rapidly expanding equatorial coronal hole, and the wind was still accelerating at this distance. The measured circulation of the wind around the Sun, peaking at 35-50 km/s, exceed classical predictions of a few km/s, challenging models of circulation in the corona and calling into question our understanding of how stars lose angular momentum and spin down as they age. Plasma-wave measurements suggest the existence of electron and ion velocity-space micro-instabilities associated with with plasma heating and thermalization processes. Not many energetic particle events were observed over the first encounter, while the white light imager observed pseudostreamer and streamer stalks emitting small intermittent blobs, potential evidence of reconnection.