The Electron Temperature and Anisotropy in the Solar Wind. Comparison of the Core and Halo Populations

0463539 - ASÚ 2017 RIV NL eng J - Journal Article
Pierrard, V. - Lazar, M. - Poedts, S. - Štverák, Štěpán - Maksimovic, M. - Trávníček, Pavel M.
The Electron Temperature and Anisotropy in the Solar Wind. Comparison of the Core and Halo Populations.
Solar Physics. Roč. 291, č. 7 (2016), s. 2165-2179. ISSN 0038-0938. E-ISSN 1573-093X
R&D Projects: GA ČR GA15-17490S
Institutional support: RVO:67985815
Keywords : solar wind * electron velocity distributions * temperature anisotropy
Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics
Impact factor: 2.682, year: 2016

This article presents a detailed observational analysis of these two components, providing estimations of their temperatures and temperature anisotropies, and decoding any potential interdependence that their properties may indicate. The dataset used in this study includes more than 120 000 of the distributions measured by three missions in the ecliptic within an extended range of heliocentric distances from 0.3 to over 4 AU. The core temperature is found to decrease with the radial distance, while the halo temperature slightly increases, clarifying an apparent contradiction in previous observational analyses and providing valuable clues about the temperature of the kappa-distributed populations. For low values of the power-index kappa, these two components manifest a clear tendency to deviate from isotropy in the same direction, which seems to confirm the existence of mechanisms with similar effects on both components, e.g., the solar wind expansion, or the particle heating by the fluctuations. However, the existence of plasma states with anticorrelated anisotropies of the core and halo populations and the increase in their number for high values of the power-index kappa suggest a dynamic interplay of these components, mediated, most probably, by the anisotropy-driven instabilities.
Permanent Link: http://hdl.handle.net/11104/0262710