@article{Matteini:2013:10.1002/jgra.50320,
author = {Matteini, L and Hellinger, P and Goldstein, BE and Landi, S and Velli, M and Neugebauer, M},
doi = {10.1002/jgra.50320},
journal = {Journal of Geophysical Research: Space Physics},
pages = {2771--2782},
title = {Signatures of kinetic instabilities in the solar wind},
url = {http://dx.doi.org/10.1002/jgra.50320},
volume = {118},
year = {2013}
}

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TY  - JOUR
AB  - <jats:p>An analysis of ion nonthermal properties in the fast solar wind based on Ulysses data is reported. The radial evolution of the main proton moments (density, temperature, and drift velocities) and their empirical correlations with other plasma parameters are investigated in detail and compared with theoretical expectations. The stability of the plasma is studied against different ion kinetic instabilities driven by ion temperature anisotropies and differential velocities, focusing on the identification of possible signatures of relevant instabilities in the observed corebeam structure of proton distributions. The temperature anisotropy of the total proton distribution appears to be constrained by fire hose instabilities, in agreement with previous studies, while if considered separately, beam and core populations exhibit opposite anisotropies, with core protons characterized by perpendicular temperatures larger than the parallel ones, possibly (marginally) unstable for ioncyclotron instability. The evolution with distance of the drift velocity between the secondary population and the main core is found to be nonadiabatic, leading to the identification of a marginal stability path of a magnetosonic ionbeam instability. As a conclusion, we find that a large fraction of the proton distributions observed by Ulysses display signatures of either a beam or a fire hose instability, suggesting that such kinetic processes play an important role in regulating the solar wind thermal energetics during the plasma expansion.</jats:p>
AU  - Matteini,L
AU  - Hellinger,P
AU  - Goldstein,BE
AU  - Landi,S
AU  - Velli,M
AU  - Neugebauer,M
DO  - 10.1002/jgra.50320
EP  - 2782
PY  - 2013///
SN  - 2169-9380
SP  - 2771
TI  - Signatures of kinetic instabilities in the solar wind
T2  - Journal of Geophysical Research: Space Physics
UR  - http://dx.doi.org/10.1002/jgra.50320
VL  - 118
ER  - 

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