In collision-poor space plasmas protons with an excess of kinetic energy or temperature in direction perpendicular to background magnetic field can excite the electromagnetic ion cyclotron (EMIC) instability. This instability is expected to be highly sensitive to suprathermal protons, which enhance the high-energy tails of the observed velocity distributions and are well reproduced by the (bi-)Kappa distribution functions. In this paper we present the results of a refined quasilinear (QL) approach, able to describe the effects of suprathermal protons on the extended temporal evolution of EMIC instability. It is thus shown that suprathermals have a systematic stimulating effect on the EMIC instability, enhancing not only the growth rates and the range of unstable wave-numbers, but also the magnetic fluctuating energy density reached at the saturation. In effect, the relaxation of anisotropic temperature becomes also more efficient, i.e., faster in time and closer to isotropy.
In the absence of efficient collisions, deviations from thermal equilibrium of plasma particle distributions are controlled by the self-generated instabilities. The whistler instability is a notorious example, usually responsible for the regulation of electron temperature anisotropy $A = T_{\perp}/T_\parallel>$ (with $\perp, \parallel$ respective to the magnetic field direction) observed in space plasmas, e.g., solar wind and planetary magnetospheres. Suprathermal electrons present in these environments change the plasma dispersion and stability properties, with expected consequences on the ki…
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 investigat…
This letter presents the results of an advanced parametrization of the solar wind electron temperature anisotropy and the instabilities resulting from the interplay of the (bi-)Maxwellian core and (bi-)Kappa halo populations in the slow solar wind. A large set of observational data (from the Ulysses, Helios and Cluster missions) is used to parametrize these components and establish their correlations. The instabilities are significantly stimulated in the presence of suprathermals, and the instability thresholds shape the limits of the temperature anisotropy for both the core and halo populatio…
X-Ray Spectroscopy for Characterizing Stimulated Raman Scattering in Inertial Confinement Fusion
Key Laboratory of Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University（四川大学核科学技术学院辐射物理与技术教育部重点实验室）；National Key Laboratory of Plasma Physics, Laser Fusion Research Center, China Academy of Engineering Physics（中国工程物理研究院激光聚变研究中心等离子体物理全国重点实验室）；College of Intelligent Manufacturing, Sichuan University of Arts and Science（四川文理学院智能制造学院）
The indefinite increase of temperature predicted by the solar wind expansion in the direction parallel to the interplanetary magnetic field is already notorious for not being confirmed by the observations. In hot and dilute plasmas from space particle-particle collisions are not efficient in constraining large deviations from isotropy, but the resulting firehose instability provides in this case plausible limitations for the temperature anisotropy of the thermal (core) populations of both the electron and proton species. The present paper takes into discussion the suprathermal (halo) electrons…
This paper summarizes the results of experiments on electron cyclotron emission (ECE) measurements at the fundamental harmonic recently performed at the axially symmetric magnetic mirror device GDT (Budker Institute, Novosibirsk). New ECE diagnostics is installed to facilitate the successful electron cyclotron resonance heating experiment and operates in the vicinity of the heating frequency of 54.5 GHz. Besides expected emission of thermal electrons, a clearly resolved non-thermal ECE is observed indicating the presence of suprathermal electrons driven by high-power microwave heating. The par…
In the solar wind electron velocity distributions reveal two counter-moving populations which may induce electromagnetic (EM) beaming instabilities known as heat flux instabilities. Depending on plasma parameters two distinct branches of whistler and firehose instabilities can be excited. These instabilities are invoked in many scenarios, but their interplay is still poorly understood. An exact numerical analysis is performed to resolve the linear Vlasov-Maxwell dispersion and characterize these two instabilities, e.g., growth rates, wave frequencies and thresholds, enabling to identify their …
Context. Recent studies on Kappa distribution functions invoked in space plasma applications have emphasized two alternative approaches which may assume the temperature parameter either dependent or independent of the power-index $κ$. Each of them can obtain justification in different scenarios involving Kappa-distributed plasmas, but direct evidences supporting any of these two alternatives with measurements from laboratory or natural plasmas are not available yet. Aims. This paper aims to provide more facts on this intriguing issue from direct fitting measurements of suprathermal electron po…
Quasi-linear approach of bi-Kappa distributed electrons with dynamic $κ$ parameter. EMEC instability
Universidad de Chile（智利大学）；KU Leuven（荷语鲁汶大学）；Ruhr-Universität Bochum（波鸿鲁尔大学）；University of Maryland, College Park（马里兰大学帕克分校）；Comisión Chilena de Energía Nuclear（智利国家核能委员会）；Universidad Andres Bello（安德烈斯贝略大学）；University of Maria Curie-Skłodowska（玛丽亚·居里-斯克沃多夫斯卡大学）
The study of parametric instabilities has played a crucial role in understanding energy transfer to plasma and, with that, the development of key applications such as inertial confinement fusion. When the densities are between $0.108n_c\lesssim n_e\lesssim 0.138n_c$ and the electron temperature is $T_e=$2.5 keV, anomalous hot electrons with kinetic energies above 100 keV are generated. Here, a new electron acceleration mechanism - the anti-Stokes Langmuir decay instability cascade of forward stimulated Raman scattering - is investigated. This mechanism not only explains anomalous energetic ele…
Ion cyclotron emission (ICE) was the first collective radiative instability, driven by confined fusion-born ions, observed from deuterium-tritium plasmas in JET and TFTR. ICE comprises strongly suprathermal emission, which has spectral peaks at multiple ion cyclotron harmonic frequencies as evaluated at the outer mid-plane edge of tokamak plasmas. The measured intensity of ICE spectral peaks scaled linearly with measured fusion reactivity in JET. In other large tokamak plasmas, ICE is currently used as an indicator of fast ions physics. The excitation mechanism for ICE is the magnetoacoustic c…
Measurements are reported of electromagnetic emission close to the cyclotron frequency of energetic ions in JET plasmas heated by waves in the ion cyclotron range of frequencies (ICRF). Hydrogen was the majority ion species in all of these plasmas. The measurements were obtained using a sub-harmonic arc detection (SHAD) system in the transmission lines of one of the ICRF antennas. The measured ion cyclotron emission (ICE) spectra were strongly filtered by the antenna system, and typically contained sub-structure, consisting of sets of peaks with a separation of a few kHz, suggesting the excita…
Relative drifts between different species or particle populations are characteristic to solar plasma outflows, e.g., in the fast streams of the solar winds, coronal mass ejections and interplanetary shocks. This paper characterizes the dispersion and stability of the low-beta alpha/proton drifts in the absence of any intrinsic thermal anisotropies, which are usually invoked in order to stimulate various instabilities. The dispersion relations derived here describe the full spectrum of instabilities and their variations with the angle of propagation and plasma parameters. The results unveil a p…
The theory of the ion cyclotron (IC) electrostatic parametric instabilities of plasma which are driven by the elliptically polarized fast wave (FW) of the finite wavelength is developed. The growth rate of the IC quasimode decay instability, which was considered as a potential source of the generation of the high energy ions in scrape-off layer (SOL) during FW injection in tokamaks, is derived analytically for arbitrary values of the FW electric field and wavelengths of the unstable IC perturbations. The comprehensive numerical analysis of the dispersion equation for three wave system which co…
This paper summarizes the studies of plasma kinetic instabilities in the electron cyclotron frequency range carried out over the last decade at the Institute of Applied Physics of Russian Academy of Sciences. We investigate the nonequilibrium plasma created and sustained by high-power microwave radiation of a gyrotron under the electron cyclotron resonance condition. Resonant plasma heating results in the formation of at least two electron components, one of which, more dense and cold, determines the dispersion properties of the high-frequency waves, and the second, a small group of energetic …
The velocity particle distributions measured in-situ in space plasmas deviate from Maxwellian (thermal) equilibrium, showing enhanced suprathermal tails which are well described by the standard Kappa-distribution (SKD). Despite its successful application, the SKD is frequently disputed due to a series of unphysical implications like diverging velocity moments, preventing a macroscopic description of the plasma. The regularized Kappa-distribution (RKD) has been introduced to overcome these limitations, but the dispersion properties of RKD-plasmas are not explored yet. In the present paper we co…
Kappa distributions are ubiquitous in space and astrophysical poorly collisional plasmas, such as the solar wind, suggesting that microscopic and macroscopic properties of these non-equilibrium plasmas are highly conditioned by the wave-particle interactions. The present work addresses the evolution of anisotropic bi-Kappa (or bi-$κ$-)distributions of electrons triggering instabilities of electromagnetic electron-cyclotron (or whistler) modes. The new quasi-linear approach proposed here includes time variations of the $κ$ parameter during the relaxation of temperature anisotropy. Numerical res…
