Temperature Fluctuation at the Sun and Large-scale Electric Field in Solar Wind: A Challenge for the Parker Solar Probe Mission

• Published in: The Astrophysical journal Vol. 882; no. 1; pp. 28 - 33
• Main Authors: Pavan, J., Viñas, A. F.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.09.2019; IOP Publishing
• Subjects: Advection; Astrophysics; Electric fields; In situ measurement; Interplanetary particle acceleration; Kappa mechanism; Kinetic equations; Parallel field; Solar coronal transients; Solar probes; Solar wind; Solar wind velocity; Sun; Two dimensional models; Variation; Velocity; Wind power generation; Wind speed; Wind velocities
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab2fcd

Velocity distributions of particles are key elements in the study of solar wind. The physical mechanisms that regulate their many features are a matter of debate. The present work addresses the subject with a fully analytical method in order to establish the shape of particle velocity distributions in solar wind. The method consists of solving the steady-state kinetic equation for particles and the related fluid equations, with spatial profiles for density and temperature that match general observational data. The model is one-dimensional in configuration-space and two-dimensional in velocity-space, and accounts for large-scale processes, namely, advection, gravity, magnetic mirroring, and the large-scale ambipolar electric field. The findings reported add to the general understanding of regulation of particle distributions in solar wind and to the predictions of their shape in regions restricted for in situ measurements. In particular, the results suggest that fluctuations of temperature at the Sun might play a key role in shaping solar wind velocity distributions via large-scale ambipolar electric field.