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Authors: Pavan J., and Viñas A. F.
Title: Temperature Fluctuation at the Sun and Large-scale Electric Field in Solar Wind: A Challenge for the Parker Solar Probe Mission

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 o. . .
Date: 09/2019 Publisher: The Astrophysical Journal Pages: 28 DOI: 10.3847/1538-4357/ab2fcd
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Authors: Perrone Denise, Stansby D, Horbury T S, and Matteini L
Title: Thermodynamics of pure fast solar wind: radial evolution of the temperature–speed relationship in the inner heliosphereABSTRACT

A strong correlation between speed and proton temperature has been observed, across many years, on hourly averaged measurements in the solar wind. Here, we show that this relationship is also observed at a smaller scale on intervals of a few days, within a single stream. Following the radial evolution of a well-defined stream of coronal-hole plasma, we show that the temperature-speed (T-V) relationship evolves with distance, implying that the T-V relationship at 1 au cannot be used as a proxy for that near the Sun. We suggest that this behaviour could be a combination of the anticorrelation between speed and flux-tube expansion factor near the Sun and the effect of a continuous heating experienced by the plasma during the expansion. We also show that the cooling index for the radial evo. . .
Date: 09/2019 Publisher: Monthly Notices of the Royal Astronomical Society Pages: 2380 - 2386 DOI: 10.1093/mnras/stz1877 Available at:
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Authors: Balat-Pichelin M., Eck J., and Sans J.L.
Title: Thermal radiative properties of carbon materials under high temperature and vacuum ultra-violet (VUV) radiation for the heat shield of the Solar Probe Plus mission

The Solar Probe Plus (SP+) mission will approach the Sun as close as 9.5 solar radii in order to understand the origin of the solar corona heating and the acceleration of the solar wind. Submitted to such extreme environmental conditions, a thermal protection system is considered to protect the payload of the SP+ spacecraft. Carbon-based materials are good candidate to fulfill this role and critical point remains the equilibrium temperature reached at perihelion by the heat shield. In this paper, experimental results obtained for the solar absorptivity α, the total hemispherical emissivity ɛ and its ratio α/ɛ, conditioning the equilibrium temperature of the thermal protection system, are presented for different kinds of carbon materials heated at . . .
Date: 01/2012 Publisher: Applied Surface Science Pages: 2829 - 2835 DOI: 10.1016/j.apsusc.2011.10.142 Available at:
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