TY  - JOUR
A1  - Vafin, Sergei
A1  - Lazar, M.
A1  - Fichtner, H.
A1  - Schlickeiser, R.
A1  - Drillisch, M.
T1  - Solar wind temperature anisotropy constraints from streaming instabilities
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Due to the relatively low rate of particle-particle collisions in the solar wind, kinetic instabilities (e.g., the mirror and firehose) play an important role in regulating large deviations from temperature isotropy. These instabilities operate in the high beta(parallel to) > 1 plasmas, and cannot explain the other limits of the temperature anisotropy reported by observations in the low beta beta(parallel to) < 1 regimes. However, the instability conditions are drastically modified in the presence of streaming (or counterstreaming) components, which are ubiquitous in space plasmas. These effects have been analyzed for the solar wind conditions in a large interval of heliospheric distances, 0.3-2.5 AU. It was found that proton counter-streams are much more crucial for plasma stability than electron ones. Moreover, new instability thresholds can potentially explain all observed bounds on the temperature anisotropy, and also the level of differential streaming in the solar wind.
KW  - solar wind
KW  - instabilities
KW  - waves
KW  - turbulence
Y1  - 2018
U6  - https://doi.org/10.1051/0004-6361/201731852
SN  - 1432-0746
VL  - 613
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Vafin, Sergei
A1  - Schlickeiser, R.
A1  - Yoon, P. H.
T1  - AMPLIFICATION OF COLLECTIVE MAGNETIC FLUCTUATIONS IN MAGNETIZED BI-MAXWELLIAN PLASMAS FOR PARALLEL WAVE VECTORS. I. ELECTRON-PROTON PLASMA
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - The general electromagnetic fluctuation theory is a powerful tool to analyze the magnetic fluctuation spectrum of a plasma. Recent works utilizing this theory for a magnetized non-relativistic isotropic Maxwellian electron-proton plasma have demonstrated that the equilibrium ratio of vertical bar delta B vertical bar/B-0 can be as high as 10(-12). This value results from the balance between spontaneous emission of fluctuations and their damping, and it is considerably smaller than the observed value vertical bar delta B vertical bar/B-0 in the solar wind at 1 au, where 10(-3) less than or similar to vertical bar delta B vertical bar/B-0 less than or similar to 10(-1). In the present manuscript, we consider an anisotropic bi-Maxwellian distribution function to investigate the effect of plasma instabilities on the magnetic field fluctuations. We demonstrate that these instabilities strongly amplify the magnetic field fluctuations and provide a sufficient mechanism to explain the observed value of vertical bar delta B vertical bar/B-0 in the solar wind at 1 au.
KW  - instabilities
KW  - magnetic fields
KW  - solar wind
KW  - turbulence
KW  - waves
Y1  - 2016
U6  - https://doi.org/10.3847/0004-637X/829/1/41
SN  - 0004-637X
SN  - 1538-4357
VL  - 829
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  -