@article{Matteini:2015:1/13,
author = {Matteini, L and Hellinger, P and Schwartz, SJ and Landi, S},
doi = {1/13},
journal = {Astrophysical Journal},
title = {FIRE HOSE INSTABILITY DRIVEN BY ALPHA PARTICLE TEMPERATURE ANISOTROPY},
url = {http://dx.doi.org/10.1088/0004-637X/812/1/13},
volume = {812},
year = {2015}
}

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TY  - JOUR
AB  - We investigate properties of a solar wind-like plasma, including a secondary alpha particle population exhibiting aparallel temperature anisotropy with respect to the background magnetic field, using linear and quasi-linearpredictions and by means of one-dimensional hybrid simulations. We show that anisotropic alpha particles candrive a parallel fire hose instability analogous to that generated by protons, but that, remarkably, can also betriggered when the parallel plasma beta of alpha particles is below unity. The wave activity generated by the alphaanisotropy affects the evolution of the more abundant protons, leading to their anisotropic heating. When both ionspecies have sufficient parallel anisotropies, both of them can drive the instability, and we observe the generationof two distinct peaks in the spectra of the fluctuations, with longer wavelengths associated to alphas and shorterones to protons. If a non-zero relative drift is present, the unstable modes propagate preferentially in the directionof the drift associated with the unstable species. The generated waves scatter particles and reduce their temperatureanisotropy to a marginally stable state, and, moreover, they significantly reduce the relative drift between the twoion populations. The coexistence of modes excited by both species leads to saturation of the plasma in distinctregions of the beta/anisotropy parameter space for protons and alpha particles, in good agreement with in situ solarwind observations. Our results confirm that fire hose instabilities are likely at work in the solar wind and limit theanisotropy of different ion species in the plasma.
AU  - Matteini,L
AU  - Hellinger,P
AU  - Schwartz,SJ
AU  - Landi,S
DO  - 1/13
PY  - 2015///
SN  - 1538-4357
TI  - FIRE HOSE INSTABILITY DRIVEN BY ALPHA PARTICLE TEMPERATURE ANISOTROPY
T2  - Astrophysical Journal
UR  - http://dx.doi.org/10.1088/0004-637X/812/1/13
UR  - http://hdl.handle.net/10044/1/28175
VL  - 812
ER  - 

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