Physics and Astronomy Calendar

I will describe measurements of velocity distribution functions and waves in the solar wind at 1 AU using instruments on NASA's WIND spacecraft and at 0.3 AU using Helios spacecraft. Plasma velocity distributions at 1 AU suggest the evolution by Coulomb collisions from nonthermal states to collisional equilibrium. Measurements at 0.3 AU are generally more nonthermal. This Coulomb coupling relationship can be used probe the plasma distributions of the inner heliosphere and suggests that the coronal population will be highly nonthermal. Furthermore, measurements of plasma waves at 1 AU suggest nonlinear evolution from a population of intense Alfven waves in the inner
heliosphere. Taken together, these observations suggest that the coronal plasma
environment is highly nonthermal and perhaps permeated by impulsive jets or waves. I will also describe the NASA Solar Probe Plus mission which will launch in summer 2018 and orbit the Sun with a final perihelion altitude of 9.8 solar radii, well within the predicted Alfven surface. Parker Solar Probe will make the first ever in situ measurements of plasma heating processes in the solar corona.