Suprathermal Particle Populations in the Solar Wind and Corona

Lazar, M.; Schlickeiser, R.; Poedts, Stefaan

doi:10.5772/39281

Cited by 19 publications

(24 citation statements)

References 61 publications

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“…EMIC instability propagates nearly parallel (k k ) to the large-scale magnetic field (B 0 ) and is driven by an excess of transverse kinetic energy of ions, e.g., a temperature anisotropy T ⊥ > T . These deviations from thermal equilibrium are usually enhanced by the suprathermal ion populations, i.e., the high-energy tails of the measured distributions (Christon et al 1991;Collier et al 1996;Fisk & Gloeckler 2006), which, overall, are properly described by the generalized power-law (Kappa) distribution functions (Pierrard & Lazar 2010;Lazar et al 2012). The presence of suprathermal populations is therefore expected to change the EMIC instability conditions predicted by an idealized bi-Maxwellian model.…”

Section: Introductionmentioning

confidence: 99%

The electromagnetic ion-cyclotron instability in bi-Kappa distributed plasmas

Lazar

2012

A&A

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Context. Observations regularly show low-frequency fluctuations of the interplanetary magnetic field (IMF), which are attributed to the electromagnetic ion-cyclotron (EMIC) waves generated either locally and self-consistently by the kinetic anisotropies of ions, or closer to the Sun (through a nonlinear cascade from long to short wavelengths), and transported by the super-Alfvénic solar wind. As a back reaction, ions can be pitch-angle scattered and accelerated, leading to the observed suprathermal populations, which are invariably anisotropic and are well described by the generalized Kappa models. Aims. A refined analysis is proposed for the EMIC wave instability as one of the most plausible constraints for the proton temperature anisotropy T p,⊥ > T p, , where and ⊥ denote directions relative to the stationary IMF. In the context of a strong, but not clear competition with the mirror instability that can develop in the same conditions, an advanced Kappa model is expected to provide the first realistic insights into the EMIC instability conditions in the solar wind. Methods. Because the solar wind is a poor-collisional plasma, the dispersion/stability formalism is based on the fundamental kinetic Vlasov-Maxwell equations for an nonthermal bi-Kappa distributed plasma. EMIC solutions are derived exactly numerically, providing accurate physical correlations between the maximum growth rates and the instability threshold conditions, which are here derived for the full range of values of the plasma beta, including the solar wind and magnetospheric plasma conditions. Results. The lowest thresholds (close to the marginal stability), which are the most relevant for the instability conditions, decrease with the increase in density of suprathermal populations. This is contrary to what was found before in a less general model, but it is fully predicted by the enhanced fluctuations of this instability for sufficiently low temperature anisotropies. These results furthermore support a fast and efficient EMIC instability involving the relaxation of kinetic anisotropies and (re)heating plasma particles.

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Section: Introductionmentioning

confidence: 99%

The electromagnetic ion-cyclotron instability in bi-Kappa distributed plasmas

Lazar

2012

A&A

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“…Multiple plausible scenarios have been proposed, including a coronal origin (Scudder, 1992;Pierrard et al, 1999;Viñas et al, 2000) of the suprathermals, as well as their generation by heating the resonant plasma particles by the fluctuations (Ma and Summers, 1998) transported by the super-Alfvénic solar wind, or the isotropisation of the field-aligned streams (also known as strahls) by the selfgenerated instabilities (Maksimovic et al, 2005;Gary and Saito, 2007;Pagel et al, 2007;Pierrard et al, 2011;Vocks, 2012;Pavan et al, 2013). Not only the origin of these two components is still controversial, but also their interplay and subsequent implication in the solar wind dynamics remains unclear (Lin, 1998;Lazar, Schlickeiser, and Poedts, 2012).…”

Section: Introductionmentioning

confidence: 99%

The Electron Temperature and Anisotropy in the Solar Wind. Comparison of the Core and Halo Populations

et al. 2016

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Estimating the temperature of the solar wind particles and their anisotropies is particularly important for understanding the origin of these deviations from thermal equilibrium as well as their effects. In the absence of energetic events the velocity distribution of electrons reveal a dual structure with a thermal (Maxwellian) core and a suprathermal (Kappa) halo. This paper presents a detailed observational analysis of these two components, providing estimations of their temperatures and temperature anisotropies and decoding any potential interdependence that their properties may indicate. The data set used in this study includes more than 120 000 the events detected by three missions in the ecliptic within an extended range of heliocentric distances from 0.3 to over 4 AU. The anti-correlation found for the core and halo temperatures is consistent with the radial evolution of the Kappa model, clarifying an apparent contradiction in previous observational analysis and providing valuable clues about the temperature of the Kappa-distributed populations. However, these two components manifest a clear tendency to deviate from isotropy in the same direction, that seems to confirm the existence of mechanisms with similar effects on both components, e.g., the solar wind expansion, or the particle heating by the fluctuations. On the other hand, the existence of plasma states with anti-correlated anisotropies of the core and halo populations suggests a dynamic interplay of these components, mediated, most probably, by the anisotropy-driven instabilities.

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“…[24] for an idealized LDM plasma with anisotropic bi-Maxwellian particles, while here we generalize the approach by assuming both the electron and ion (proton) populations well described by bi-Kappa distributions in velocity space. The generalized Kappa power-laws are more appropriate to reproduce the velocity distributions with enhanced high-energy tails, which are frequently reported by the in-situ measurements in space plasmas, i.e., the solar wind and planetary magnetospheres [25,26]. On the other hand, cyclotron instabilities have been extensively investigated, but only in bi-Kappa plasmas embedded in a uniform magnetic field [15][16][17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Cyclotron Electromagnetic Instabilities in a Laboratory Dipole Magnetospheric Plasma with bi-Kappa Distributions

Grishanov

Azarenkov

Lazar

2017

Plasma and Fusion Research

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The transverse dielectric susceptibility elements are derived for electromagnetic cyclotron waves in an axisymmetric laboratory dipole magnetosphere accounting for the cyclotron and bounce resonances of trapped and untrapped particles. A bi-Kappa (or bi-Lorentzian) distribution function is invoked to model the energetic particles with anisotropic temperature. The steady-state two-dimensional (2D) magnetic field is modeled by laboratory dipole approximation for a superconducting ring current of finite radius. Derived for field-aligned circularlypolarized waves the dispersion relations are suitable for analyzing both the whistler instability in the range below the electron-cyclotron frequency, and the proton-cyclotron instability in the range below the ion-cyclotron frequency. The instability growth rates in the 2D laboratory magnetosphere are defined by the contributions of energetic particles to the imaginary part of transverse susceptibility.

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Suprathermal Particle Populations in the Solar Wind and Corona

Cited by 19 publications

References 61 publications

The electromagnetic ion-cyclotron instability in bi-Kappa distributed plasmas

The electromagnetic ion-cyclotron instability in bi-Kappa distributed plasmas

The Electron Temperature and Anisotropy in the Solar Wind. Comparison of the Core and Halo Populations

Cyclotron Electromagnetic Instabilities in a Laboratory Dipole Magnetospheric Plasma with bi-Kappa Distributions

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