Ion temperature anisotropy limitation in high beta plasmas

Scime, Earl; Keiter, P. A.; Balkey, M. M.; Boivin, Robert; Kline, J. L.; Blackburn, M.; Gary, S. Peter

doi:10.1063/1.874036

Cited by 65 publications

(63 citation statements)

References 34 publications

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“…In the latter environment, these instabilities not only modify the thermodynamics of the plasma (as in the solar wind), but they also play a crucial dynamical role, regulating the anisotropic stress that helps transport angular momentum, allowing accretion to proceed. vice, where isotropization and magnetic fluctuations were observed corresponding to the Alfvén ion cyclotron instability [6]. Similar results were obtained in the solar wind at 1 AU [7] (for T ⊥ /T > and solar wind speeds greater than 600 km/s), suggesting that the proton cyclotron instability plays a role.…”

supporting

confidence: 73%

“…Growth of ion temperature anisotropy instabilities has been studied in a (relatively collisional) laboratory de-vice, where isotropization and magnetic fluctuations were observed corresponding to the Alfvén ion cyclotron instability [6]. Similar results were obtained in the solar wind at 1 AU [7] (for T ⊥ /T > and solar wind speeds greater than 600 km/s), suggesting that the proton cyclotron instability plays a role.…”

supporting

confidence: 64%

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Magnetic Fluctuation Power Near Proton Temperature Anisotropy Instability Thresholds in the Solar Wind

et al. 2009

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The proton temperature anisotropy in the solar wind is known to be constrained by the theoretical thresholds for pressure anisotropy-driven instabilities. Here we use approximately 1 million independent measurements of gyroscale magnetic fluctuations in the solar wind to show for the first time that these fluctuations are enhanced along the temperature anisotropy thresholds of the mirror, proton oblique firehose, and ion cyclotron instabilities. In addition, the measured magnetic compressibility is enhanced at high plasma beta (β 1) along the mirror instability threshold but small elsewhere, consistent with expectations of the mirror mode. The power in this frequency (the 'dissipation') range is often considered to be driven by the solar wind turbulent cascade, an interpretation which should be qualified in light of the present results. In particular, we show that the short wavelength magnetic fluctuation power is a strong function of collisionality, which relaxes the temperature anisotropy away from the instability conditions and reduces correspondingly the fluctuation power.PACS numbers: 96.50. Ci, 52.35.Ra, 95.30.Qd The physical processes that regulate the expansion of the super-Alfvénic solar wind into space include adiabatic particle motion, plasma instabilities, and binary particle collisions. As the wind expands, plasma density n p and magnetic field |B| decrease radially. The Chew-Goldberger-Low (CGL) relations [1] predict that the plasma ions should become anisotropic in the sense of T > T ⊥ if the particle motion is adiabatic and collisionless; here T is the ion temperature parallel and perpendicular to the background magnetic field. However, Coulomb collisions and pressure-anisotropy instabilities act to pitch-angle scatter the plasma back towards isotropy [2]. At 1 AU, the most probable value of the proton temperature anisotropy is T ⊥ /T ≈ 0.89 (see Figure 1, top panel below). If CGL were valid, this would imply a proton temperature anisotropy of T ⊥ /T ≥ 200 at 5 solar radii.The same pressure-anisotropy instabilities that operate in the solar wind are believed to operate in other low-collisionality astrophysical plasmas, including clusters of galaxies [3] and some accretion disks onto black holes [4,5]. In the latter environment, these instabilities not only modify the thermodynamics of the plasma (as in the solar wind), but they also play a crucial dynamical role, regulating the anisotropic stress that helps transport angular momentum, allowing accretion to proceed. vice, where isotropization and magnetic fluctuations were observed corresponding to the Alfvén ion cyclotron instability [6]. Similar results were obtained in the solar wind at 1 AU [7] (for T ⊥ /T > and solar wind speeds greater than 600 km/s), suggesting that the proton cyclotron instability plays a role. Both mirror mode and ion cyclotron anisotropy instabilities appear to be active in the terrestrial magnetosheath, inferred from observed constraints on the temperature anisotropy [8,9]. More recently, Kasper et al. Growth of ion...

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supporting

confidence: 73%

supporting

confidence: 64%

Magnetic Fluctuation Power Near Proton Temperature Anisotropy Instability Thresholds in the Solar Wind

et al. 2009

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“…Gary et al (1994d) extended the marginal stability analysis, or the inverse relationship, to include helium cyclotron anisotropy instability in the magnetosheath. Scime et al (2000) confirmed the validity of the inverse relationship on the basis of laboratory plasma experiment. Pantellini and Schwartz (1995) and Pokhotelov et al (2000) extended the model to include isotropic electrons and anisotropic ions.…”

Section: Introductionsupporting

confidence: 62%

Kinetic instabilities in the solar wind driven by temperature anisotropies

Yoon

2017

Rev. Mod. Plasma Phys.

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The present paper comprises a review of kinetic instabilities that may be operative in the solar wind, and how they influence the dynamics thereof. The review is limited to collective plasma instabilities driven by the temperature anisotropies. To limit the scope even further, the discussion is restricted to the temperature anisotropy-driven instabilities within the model of bi-Maxwellian plasma velocity distribution function. The effects of multiple particle species or the influence of field-aligned drift will not be included. The field-aligned drift or beam is particularly prominent for the solar wind electrons, and thus ignoring its effect leaves out a vast portion of important physics. Nevertheless, for the sake of limiting the scope, this effect will not be discussed. The exposition is within the context of linear and quasilinear Vlasov kinetic theories. The discussion does not cover either computer simulations or data analyses of observations, in any systematic manner, although references will be made to published works pertaining to these methods. The scientific rationale for the present analysis is that the anisotropic temperatures associated with charged particles are pervasively detected in the solar wind, and it is one of the key contemporary scientific research topics to correctly characterize how such anisotropies are generated, maintained, and regulated in the solar wind. The present article aims to provide an up-to-date theoretical development on this research topic, largely based on the author's own work.

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“…Scime et al [5] and Biloiu et al [6] have also developed optical tomography apparatus. The development of diode lasers [7] allowed the use of less expensive lasers (compared to dye lasers) in this work.…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional ion velocity distribution functions in inductively coupled argon plasma

Zimmerman

McWilliams

Edrich

2005

Plasma Sources Sci. Technol.

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Two-dimensional ion velocity distribution functions (IVDFs) of argon plasmas have been measured with optical tomography via laser-induced fluorescence (LIF). An inductive radio-frequency (RF) coil created the plasmas, and IVDFs were measured versus RF frequency, gas pressure and location (bulk plasma or presheath of a plate). Typical gas pressure was 0.3-0.4 mTorr, RF power 25 W and magnetic field 130 G. Effective perpendicular ion temperature decreased with increasing RF frequency, and changed little with pressure. Optical tomography reveals features of the presheath IVDF that cannot be deduced from LIF scans parallel and perpendicular to the plate alone. Progress also has been made toward performing optical tomography on a commercial ion beam source (Veeco/Ion Tech 3 cm RF Ion Source, Model #201). In particular, it has been discovered that the beam energy fluctuates in a range of about 20 eV over the timescale of a few minutes.

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Ion temperature anisotropy limitation in high beta plasmas

Cited by 65 publications

References 34 publications

Magnetic Fluctuation Power Near Proton Temperature Anisotropy Instability Thresholds in the Solar Wind

Magnetic Fluctuation Power Near Proton Temperature Anisotropy Instability Thresholds in the Solar Wind

Kinetic instabilities in the solar wind driven by temperature anisotropies

Two-dimensional ion velocity distribution functions in inductively coupled argon plasma

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