Effects of suprathermal electrons on the proton temperature anisotropy in space plasmas: Electromagnetic ion-cyclotron instability

In collision-poor plasmas from space, e.g., the solar wind and planetary magnetospheres, the kinetic anisotropy of the plasma particles is expected to be regulated by the kinetic instabilities. Driven by an excess of ion (proton) temperature perpendicular to the magnetic field $(~T_\perp >T_\parallel)$, the electromagnetic ion-cyclotron (EMIC) instability is fast enough to constrain the proton anisotropy, but the observations do not conform to the instability thresholds predicted by the standard theory for bi-Maxwellian models of the plasma particles. This paper presents an extended investigation of the EMIC instability in the presence of suprathermal electrons which are ubiquitous in these environments. The analysis is based on the kinetic (Vlasov-Maxwell) theory assuming that both species, protons and electrons, may be anisotropic, and the EMIC unstable solutions are derived numerically providing an accurate description for conditions typically encountered in space plasmas. The effects of suprathermal populations are triggered by the electron anisotropy and the temperature contrast between electrons and protons. For certain conditions the anisotropy thresholds exceed the limits of the proton anisotropy measured in the solar wind considerably restraining the unstable regimes of the EMIC modes.Comment: Accepted for publication in Astrophysics and space scienc

Kinetic equations for thermal degradation of polymers

Kinetic equations are analyzed for thermal degradation of polymers. The governing relations are based on the fragmentation-annihilation concept. Explicit solutions to these equations are derived in two particular cases of interest. For arbitrary values of adjustable parameters, the evolution of the number-average and mass-average molecular weights of polymers is analyzed numerically. Good agreement is demonstrated between the results of numerical simulation and experimental data. It is revealed that the model can correctly predict observations in thermo-gravimetric tests when its parameters are determined by matching experimental data for the decrease in molecular weight with exposure time

Distribution of estrogen receptor in the rabbit cervix during pregnancy with special reference to stromal elements: an immunohistochemical study

Abstract The estrogen plays a critical role during pregnancy through their receptors. Although the rabbit is one of the most important lab animal estrogen receptor alpha (ERA) localization on basic cells, newly discovered cells including telocyte and neuroendocrine cells, vascular compartments and interstitium during pregnancy not been described. At 0 day pregnancy, the most prominent immunoreactivity was moderate to ERA and observed on the ciliated cells, secretory cells, blood plasma, and interstitium. The smooth muscles and the endothelial cells showed mild immunoreactivity to ERA. Lymphocytes only exhibited strong immunoreactivity to ERA. At 7 days pregnancy moderate immunoreactivity to ERA observed on ciliated cells, secretory cells, smooth muscles, interstitium, and lymphocytes. Strong immunoreactivity to ERA detected on endothelial cells and blood plasma. At 14 days of pregnancy, the most prominent immunoreactivity was strong and detected on ciliated cells, smooth muscles, lymphocytes, and interstitium. Moderate immunoreactivity detected on endothelial cells and blood plasma. Secretory cells only exhibited mild immunoreactivity to ERA. At 21 days of pregnancy, the immunoreactivity to ERA ranged between mild on ciliated cells, smooth muscles, blood plasma and interstitium and negative on secretory cells, endothelial cells and lymphocytes. Our results indicated that the frequency and intensity of ERA immunostaining in the rabbit cervix varied on different structural compartments of the cervix during different pregnancy stages

EFFECTS OF ELECTRONS ON THE ELECTROMAGNETIC ION CYCLOTRON INSTABILITY: SOLAR WIND IMPLICATIONS

© 2015. The American Astronomical Society. All rights reserved.. In diffuse plasmas in space, particle-particle collisions are rare and inefficient, such that a plausible mechanism for constraining the temperature anisotropy of plasma particles may be provided by the resulting instabilities. The implication of the electromagnetic ion-cyclotron (EMIC) instability in the solar wind is still unclear because this instability is fast enough to relax the proton temperature anisotropy, but the 1 AU measurements do not conform to the instability thresholds predicted by the existing theories, which ignore the kinetic effects of electrons, assuming them to be isotropic. This paper presents a refined analysis of the EMIC instability in the presence of a temperature (T) anisotropy of electron (subscript "e") population, i.e., enabling the identification of two distinct regimes of this instability that correspond to an excess of perpendicular temperature () or an excess of parallel temperature (). The growth rates, real frequencies, and threshold conditions are found to be highly sensitive to the electron temperature anisotropy, and electrons with inhibit the instability, while for the instability growth rates increase with the electron anisotropy. Moreover, the electron-proton temperature ratio becomes an important factor that stimulates the effect of the anisotropic electrons. The potential relevance of the new results in the solar wind is analyzed by contrasting the instability thresholds with the observed limits of the proton temperature anisotropy.status: publishe

The interplay of the solar wind proton core and halo populations: EMIC instability

©2016. American Geophysical Union. All Rights Reserved. The kinetic properties of the solar wind protons (ions), like their temperature anisotropy and the resulting instabilities, are, in general, investigated considering only the proton core (or thermal) populations. The implication of the suprathermal halo components is minimized or just ignored, despite the fact that their presence in the solar wind is continuously reported by the observations, and their kinetic energy density may be significant. Whether they are originating in the corona or solar wind, the energetic particles may result from acceleration by the plasma turbulence or from the pitch angle scattering of the streaming protons by the self-generated fluctuations. The presence of suprathermal protons in the heliosphere suggests, therefore, a direct implication in resonant interactions, e.g., Landau and cyclotron, with plasma particles. This paper presents the results of a first investigation on the interplay of the proton core and suprathermal halo, when both these two populations may exhibit temperature anisotropies, which destabilize the electromagnetic ion (proton) cyclotron (EMIC) modes. These results clearly show that for conditions typically encountered in the solar wind, the effects of the suprathermals can be more important than those driven by the core. Remarkable are also the cumulative effects of the core and halo components, which change dramatically the instability conditions.status: publishe

Plasma Parameters Effects on Dust Acoustic Solitary Waves in Dusty Plasmas of Four Components

The presence and propagation of dust-acoustic solitary waves in dusty plasma contains four components such as negative and positive dust species beside ions and electrons are studied. Both the ions and electrons distributions are represented applying nonextensive formula. Employing the reductive perturbation method, an evolution equation is derived to describe the small-amplitude dust-acoustic solitons in the considered plasma system. The used reductive perturbation stretches lead to the nonlinear KdV and modified KdV equations with nonlinear and dispersion coefficients that depend on the parameters of the plasma. This study represents that the presence of compressive or/and rarefactive solitary waves depends mainly on the value of the first-order nonlinear coefficient. The structure of envelope wave is undefined for first-order nonlinear coefficient tends to vanish. The coexistence of the two types of solitary waves appears by increasing the strength of nonlinearity to the second order using the modified KdV equation