A two-dimensional Alfvén wave–driven solar wind model with proton temperature anisotropy

Using two-dimensional hybrid expanding box simulations we study the competition between the continuously driven parallel proton temperature anisotropy and fire hose instabilities in collisionless homogeneous plasmas. For a quasi-radial ambient magnetic field the expansion drives $T_{p\Vert }>T_{p\bot }$ and the system becomes eventually unstable with respect to the dominant parallel fire hose instability. This instability is generally unable to counteract the induced anisotropization and the system typically becomes unstable with respect to the oblique fire hose instability later on. The oblique instability efficiently reduces the anisotropy and the system rapidly stabilizes, while a significant part of the generated electromagnetic fluctuations is damped to protons. As long as the magnetic field is in the quasi-radial direction, this evolution repeats itself and the electromagnetic fluctuations accumulate. For a sufficiently oblique magnetic field the expansion drives $T_{p\bot }>T_{p\Vert }$ and brings the system to the stable region with respect to the fire hose instabilities.

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Linear and Nonlinear Effects of Proton Temperature Anisotropy on Proton-beam Instability in the Solar Wind

The Astrophysical Journal ◽

10.3847/1538-4357/ac02bc ◽

2021 ◽

Vol 916 (1) ◽

pp. 30

Author(s):

L. Xiang ◽

K. H. Lee ◽

D. J. Wu ◽

H. W. Yu ◽

L. C. Lee

Keyword(s):

Solar Wind ◽

Proton Beam ◽

Nonlinear Effects ◽

Beam Instability ◽

Temperature Anisotropy ◽

Proton Temperature ◽

Linear And Nonlinear

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The Downwind Solar Wind: Model Comparison with Pioneer 10 Observations

The Astrophysical Journal ◽

10.3847/2041-8213/abb81e ◽

2020 ◽

Vol 901 (2) ◽

pp. L23

Author(s):

M. Nakanotani ◽

G. P. Zank ◽

L. Adhikari ◽

L.-L. Zhao ◽

J. Giacalone ◽

...

Keyword(s):

Solar Wind ◽

Model Comparison ◽

Wind Model ◽

Solar Wind Model ◽

Pioneer 10

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Proton temperature-anisotropy-driven instabilities in weakly collisional plasmas: Hybrid simulations

Journal of Plasma Physics ◽

10.1017/s0022377814000634 ◽

2014 ◽

Vol 81 (1) ◽

Cited By ~ 18

Author(s):

Petr Hellinger ◽

Pavel M. Trávníček

Keyword(s):

Magnetic Field ◽

Langevin Equation ◽

Transport Coefficients ◽

Two Dimensional ◽

Temperature Anisotropy ◽

Coulomb Collisions ◽

Proton Temperature ◽

Collisionless Plasmas ◽

High Beta ◽

Kinetic Instabilities

Kinetic instabilities in weakly collisional, high beta plasmas are investigated using two-dimensional hybrid expanding box simulations with Coulomb collisions modeled through the Langevin equation (corresponding to the Fokker-Planck one). The expansion drives a parallel or perpendicular temperature anisotropy (depending on the orientation of the ambient magnetic field). For the chosen parameters the Coulomb collisions are important with respect to the driver but are not strong enough to keep the system stable with respect to instabilities driven by the proton temperature anisotropy. In the case of the parallel temperature anisotropy the dominant oblique fire hose instability efficiently reduces the anisotropy in a quasilinear manner. In the case of the perpendicular temperature anisotropy the dominant mirror instability generates coherent compressive structures which scatter protons and reduce the temperature anisotropy. For both the cases the instabilities generate temporarily enough wave energy so that the corresponding (anomalous) transport coefficients dominate over the collisional ones and their properties are similar to those in collisionless plasmas.

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