Space Plasmas Research Articles

Effects of Nonzero-frequency Fluctuations on Turbulence Spectral Observations

In situ observations of turbulence spectra in space plasmas are usually interpreted as wavenumber spectra, assuming that the fluctuation frequency is negligible in the plasma flow frame. We explore the effects of nonzero frequency in the plasma flow frame on turbulence spectral observations. The finite frequency can be caused by either propagating waves or nonlinear broadening of nonpropagating structures. We show that the observed frequency spectrum can be modified by the nonzero frequency of turbulent fluctuations in several ways. Specifically, (i) frequency broadening results in a minor modification to the observed spectrum, primarily acting as a smoothing kernel of the spectrum near the spectral break, while the asymptotic spectral index remains unchanged; (ii) wave propagation can affect the observed spectral index for anisotropic turbulence. The effect is significant at low frequencies and weaker at high frequencies, leading to a “concave” shape of the observed perpendicular spectrum; (iii) the Doppler shift for forward- and backward-propagating Elsasser modes can result in a nonzero cross helicity for critical-balanced turbulence since the effect of the Doppler shift favors outward-propagating waves systematically, resulting in an observed imbalance. These results may have important implications for the interpretation of solar wind flows observed by Parker Solar Probe.

Impact of external magnetic field on temperature anisotropy driven Weibel instability in a magnetized plasma

In this paper, we investigate the impact of an external magnetic field on the Weibel instability driven by temperature anisotropy in a magnetized plasma. The study provides the influence of electron temperature anisotropy, considering both cold as well as warm ions. We derive expressions for the growth rate Γ (s−1) in each case to quantify the effect of some specific parameters on the instability. For example, the growth rate is plotted against the magnetic field for three distinct cases: considering only electrons, including cold ions, and incorporating warm ions. It is observed that the growth rate decreases as the applied magnetic field increases. Furthermore, the addition of both cold and warm ions to the plasma significantly influences the observed effects. It can be explained as follows: in the presence of cold ions, the growth rate is decreased with an increase in the wave number kz (cm−1). In addition, a decrease in the growth rate is observed with an increasing wave number in the case of warm ions. Therefore, it can be seen that the Weibel instability, propelled by thermal anisotropy, holds significant implications owing to its prevalence in both astrophysical and laboratory plasmas. The findings presented here are expected to contribute to the advancements in magnetic field generation and particle acceleration in various astrophysical phenomena, including gamma-ray bursts, relativistic collisionless shock fronts, radio supernovae, and pulsar winds.

Radiation-driven diffusive transport of fast electrons in solar flares

Fast electron scattering on plasma ions due to stimulated Bremsstrahlung is investigated and modeled. Comparison with Coulomb scattering suggests that stimulated Bremsstrahlung scattering can be dominant in low-density, radiation-driven plasmas, provided that the radiation spectrum has a sufficiently high brightness temperature in the neighborhood of the plasma frequency. While stimulated Bremsstrahlung scattering cannot be easily observed in laboratory plasmas due to their small size, it should operate in large-scale astrophysical plasmas, such as those met in the flaring solar corona. The effect of the solar microwave radiation on fast-electron scattering is evaluated through a parameterized flaring corona model. We find that stimulated Bremsstrahlung greatly enhances the fast-electron scattering frequency in the flare magnetic loop, leading the transport of deka-keV electrons to occur in the diffusion regime, characterized by significant precipitation rates. This prediction is consistent with the interpretation of the above-loop-top hard x-ray and microwave emissions from the X3.1 flare of August 24, 2002. Our analysis indicates that stimulated Bremsstrahlung may play an essential role in the dynamics of fast electrons trapped in solar flare loops.

Localization of beam generated whistler wave and turbulence generation in reconnection region of magnetopause

Whistler waves have been studied for many years in relation to turbulence and particle heating, and observations show that they are crucial to magnetic reconnection. Recent research has revealed a close relationship between magnetic reconnection and turbulence. The current work investigates the whistler turbulence caused by the energetic electron beam in the magnetic reconnection sites of magnetopause and also due to dynamic evolution of magnetic islands. For this, we develop a model based upon the two-fluid approximation to study whistler dynamics, propagating in the medium with the pre-existing chain of magnetic islands and under the influence of background density perturbation originating from ponderomotive nonlinearity of wave. Dynamics of nonlinear whistler have been solved with pseudo-spectral approach and a finite difference method with a modified predictor–corrector method and a Runge Kutta method for the semianalytical model. In the current research, we study how the nonlinear whistler wave contributes to the significant space phenomenon, i.e., turbulence, localization, and magnetic reconnection. We have also investigated the formation of a current sheet in a magnetopause region of the order of few-electron inertial length. We analyzed the power spectrum at the magnetopause when the system reached a quasi-steady condition. Our new approach to study whistler turbulence by an energetic electron beam at the magnetic reconnection sites has extensive applications to space plasmas, shedding a new light on the study of magnetic reconnection in nature.

A Note on the Flattop Velocity Distribution in Space Plasmas

A flattop velocity distribution is one of the most characteristic distributions in space plasmas. I discuss its properties using the generalized beta-prime distribution. Then I present a sampling algorithm for generating the flattop distribution in particle-in-cell and Monte Carlo simulations.

Head on collision of multi ion acoustic solitons with arbitrary degenerate electrons

This study presents a head-on collision of ion-acoustic (IA) multiple solitons in unmagnetized quantum plasma with arbitrary degenerate electrons. The two-sided Korteweg–de Vries equations and phase shift associated with them have been derived using the extended Poincaré-Lighthill-Kuo (PLK) method. Depending on the quantum parameter’s value for the degenerate electrons, it is found that compressive and rarefactive solitons are formed. In addition, the Hirota bilinear approach is used to investigate the overtaking collision, and the expressions of phase shifts of multi-solitons interactions are determined. For a specific range of quantum diffraction, i.e, H < 2 compressional solitons propagating with supersonic speed, and for H > 2 the rarefactive solitons travelling with subsonic speed are found. A new nonlinear structure with a larger amplitude is produced during the collision in the interaction region. Graphically, the effects of different plasma parameters such as quantum diffraction and fugacity on interacting IA solitons structures and their associated phase shifts are investigated. The results of this study might help us to understand the collision of ion-acoustic solitons in an unmagnetized quantum plasma with arbitrary electrons degeneracy which can exist in astrophysical or laser plasma environment.

Mediation of collisionless turbulent dissipation through cyclotron resonance

The dissipation of turbulence in astrophysical systems is fundamental to energy transfer and heating in environments ranging from the solar wind and corona to accretion disks and the intracluster medium. Although turbulent dissipation is relatively well understood in fluid dynamics, astrophysical plasmas often exhibit exotic behaviour, arising from the lack of interparticle collisions, which complicates turbulent dissipation and heating in these systems. Recent observations by NASA’s Parker Solar Probe mission in the inner heliosphere have shed new light on the role of ion cyclotron resonance as a potential candidate for turbulent dissipation and plasma heating. Here, using in situ observations of turbulence and wave populations, we show that ion cyclotron waves provide a major pathway for dissipation and plasma heating in the solar wind. Our results support recent theoretical predictions of turbulence in the inner heliosphere, known as the helicity barrier, that suggest a role of cyclotron resonance in ion-scale dissipation. Taken together, these results provide important constraints for turbulent dissipation and acceleration efficiency in astrophysical plasmas.

Effect of Cosmic Plasma on the Observation of Supernovae Ia

In observational cosmology, a supernova Ia is used as a standard candle in order to extend the Hubble diagram to a higher redshift range. Astrophysicists found that the observed brightness of high redshift supernovae Ia is dimmer than expected. This dimming effect is considered observational evidence for the existence of dark energy in the universe. It should be noted that this conclusion is based on an assumption that the mass density of the cosmic plasma is very small. Therefore, the dimming effect caused by the Compton scattering of free electrons in cosmic plasma can be neglected. X-ray observations suggest that the mass density of the cosmic plasma may be very large. In theory, the observed dimming effect of high redshift supernovae Ia may be caused by the Compton scattering of free electrons in the cosmic plasma. In this paper it will be shown that this idea is reasonable. Therefore, there is no need to introduce the confusing concept of dark energy into cosmology.

Design and construction of the near-earth space plasma simulation system of the Space Plasma Environment Research Facility

Our earth is immersed in the near-earth space plasma environment, which plays a vital role in protecting our planet against the solar-wind impact and influencing space activities. It is significant to investigate the physical processes dominating the environment, for deepening our scientific understanding of it and improving the ability to forecast the space weather. As a crucial part of the National Major Scientific and Technological Infrastructure–Space Environment Simulation Research Infrastructure (SESRI) in Harbin, the Space Plasma Environment Research Facility (SPERF) builds a system to replicate the near-earth space plasma environment in the laboratory. The system aims to simulate the three-dimensional (3-D) structure and processes of the terrestrial magnetosphere for the first time in the world, providing a unique platform to reveal the physics of the 3-D asymmetric magnetic reconnection relevant to the earth's magnetopause, wave–particle interaction in the earth's radiation belt, particles’ dynamics during the geomagnetic storm, etc. The paper will present the engineering design and construction of the near-earth space plasma simulation system of the SPERF, with a focus on the critical technologies that have been resolved to achieve the scientific goals. Meanwhile, the possible physical issues that can be studied based on the apparatus are sketched briefly. The earth-based system is of great value in understanding the space plasma environment and supporting space exploration.

Nonlinear structure and growth rate of solitary waves for extended Zakharov-Kuznetsov equation in plasma having (r, q) distribution electrons

The Reductive Perturbation Technique (RPT) is used to investigate ion acoustic waves (IAWs) in magnetized plasmas made up of electrons obeying the generalized form of ( r,q ) distribution. The analysis makes use of the Extended Zakharov-Kuznetsov (EZK) equation and the hydrodynamic theory of plasmas. The study investigates the effects of electron flatness ( r ) at low energy and superthermal ( q ) at high energy on the characteristics of IAWs, and the solutions to the EZK equation are plotted for different values of the plasma characteristics, such as the total ion cyclotron frequency, the ion to electron temperature ratio, and the ion-specific heat. The research goes into great detail to estimate the instability threshold and growth rate of these waves by applying a small-k perturbation technique. Overall, this investigation contributes to the better understanding of ion acoustic structures in space plasmas.

Theoretical investigation of magnetic-field and hyperfine-induced transition parameters for magnesium-like and chlorine-like ions

In this paper, we report an extensive theoretical study of the magnetic-field and hyperfine-induced transition parameters for magnesium-like ions from Cr XIII to Zn XIX and chlorine-like ions from Mn IX to Co XI. These ions have a high abundance in the astrophysical plasma. Zeeman splitting level energies, hyperfine- and/or magnetic-field dependent wavelengths, and transition rates of the 3s3p 3P2,1,0→3s21S0 (for magnesium-like ions) and the 3p43d 4D7/2→ 3p52P3/2 line (for chlorine-like ions), are computed using the multiconfiguration Dirac–Fock method. Some higher-order effects, such as the Breit interaction and quantum electrodynamics corrections, are included in the relativistic configuration interaction method, as this makes the results more accurate. A comparison between the our predictions and other theoretical and experimental values is made. A satisfactory agreement is achieved. Besides providing valuable information for spectral line analysis, the present work will have a variety of implications for fusion and astrophysical plasma sources, for example, in the determination of magnetic fields in solar coronas and other stars.

STUDY OF GLOBAL STABILITY OF ROTATING PARTIALLY IONIZED PLASMA SATURATING A POROUS MEDIUM

The importance of thermal convection in rotating partially ionized plasma has been observed in various laboratory and astrophysical plasmas. The focus of this work is on the investigation of the effect of rotation on the thermal convection of partially ionized plasma within a porous medium by using nonlinear and linear analyzes. For porous medium, the Darcy-Brinkman model has been used. The eigenvalue problems for linear and nonlinear analyzes have been developed using the normal mode method and energy method, respectively. For numerical analysis, the Galerkin-weighted residual method has been employed to determine the Rayleigh-Darcy number. The effects of rotation, medium permeability, compressibility, and collisional frequency have been observed on the stability of the system. It has been found that the subcritical region does not exist, and hence global stability prevails. The rotation is found to induce oscillatory modes of convection. Rotation, medium permeability, and compressibility are found to delay the onset of convection. The collisional frequency doesn't influence the stability of the system for stationary convection; however, it does influence energy decay and oscillatory convection. All the findings of our study have been discussed and presented graphically.

XPS INVESTIGATION OF THE WORK FUNCTION OF GLASS CARBON COATINGS AFTER EXTENDED STAY ON THE INTERNATIONAL SPACE STATION (ISS)

Using XPS, the electron work function values on the surface of glassy carbon coatings of graphite samples, after an extended stay on a board of the ISS in open space conditions, were investigated. The results were compared with the characteristics of glassy carbon coatings of samples left on the ground for the same period. It was found that the electron work function does not change significantly, and this proves the possibilities of successfully application of these coatings, obtained by original Bulgarian technology, for space experiments on the board of satellites for measuring electric fields in the ionospheric-magnetospheric plasma. The minimal observed variations in the values of the electron work function are explained by small differences in the content of traces of different chemical elements on the surface of the coatings. It has been established that the glassy carbon coatings have stable characteristics after a long stay in space, despite the small fluctuations in the values of the electron work function. The results show that glassy carbon coatings are chemically and mechanically stable. The obtained results of this original technological experiment are unique for development of sensitive elements - sensors for measuring weak electric fields in the cosmic plasma.

Observations of Electron Secondary Reconnection in Magnetic Reconnection Front

Magnetic reconnection, a fundamental plasma process transforming magnetic field energy into particle energy, is ubiquitous in space and responsible for many explosive phenomena, such as solar flares and gamma-ray bursts. Recent numerical theories have predicted that reconnection fronts far from the primary reconnection region can host secondary reconnection in three-dimensional scenarios, different from the conventional two-dimensional diagram where only one X-line stands to sustain reconnection. In this study, we provide direct observational evidence for ongoing secondary reconnection in the reconnection front via the unprecedentedly high-cadence data from NASA’s MMS mission. The secondary reconnection is identified by the presence of an X-line, a super-Alfvénic electron jet, and nonideal energy dissipation. Different from the primary ion–electron reconnection, the secondary reconnection is electron-only, with its X-line quasi-perpendicular to the primary X-line. Hence reconnection, when evolving from local to global scales, becomes essentially three-dimensional with different patterns developed. These results provide crucial insights into understanding cross-scale energy transport driven by reconnection in space plasmas.

Особенности применения установок Плазменный фокус в радиационном и космическом материаловедении

The features of the use of Plasma Focus (PF) devices in the field of radiation and space materials science related to the specific generation of several types of radiation in the working chambers of the PF are considered. It is noted that the main role in the damage and modification of the structural state of the surface layers of materials irradiated in the cathode zone of the PF working chamber is played by powerful pulsed beams of working gas ions and flows of high-temperature plasma in the nano- and microsecond range of pulse duration. It is shown that in addition to the common combined beam-plasma effect on a target sample, PF installations allow the possibility of separate irradiation of the target material with ion and plasma flows. Three methods for separating pulsed flows of hot plasma and fast ions in space and time in a PF installation, described in the literature, are presented. It is noted that PF installations are a promising tool for solving fundamental and applied problems in radiation and space materials science, including for simulation experiments focused on problems of thermonuclear energy and aerospace engineering. It is also indicated that hard X-ray pulses with a duration in the nanosecond range, arising from pulsed discharges in the PF chamber, can be used for diagnosing fast processes, in particular for non-destructive flaw detection of machines and mechanisms during their operation.

Observation of rapid flux coalescence in merging field-reversed configurations

Rapid magnetic reconnection was experimentally observed to occur within a microsecond timescale, leading to the field-reversed configuration (FRC) comprising a single closed magnetic field structure. The compressibility of the plasma within the FRC played a crucial role in accelerating the coalescence process, making it considerably faster than the resistive process. A strong similarity between the observed experimental results and those of the coalescence of solar flare loops indicates that astrophysical phenomena and laboratory plasmas are governed by a common physics.

Fiber Optic Vacuum Ultraviolet Sensor Based on an AlN-Microwire Probe

Vacuum ultraviolet (VUV) light sensing shows great potential applications in the space science, materials, biophysics, and plasma physics. In this work, an all-optical detection method is proposed for VUV sensing by constructing an optical fiber-end Fabry-Pérot interferometer based on a single aluminum nitride (AlN) microwire. Compared with the traditional electrical devices, this all-optical detection method overcomes the difficulties like the fast response and electromagnetic interference immunity in detecting VUV bands at the present stage, and improves the response speed. The proposed device shows the excellent performance of VUV detection, with the static sensitivity of 1.03 nm/(W·cm−2), response rise time of down to 10 µs, and decay time of 0.64 ms. Beneficial from the excellent radiation resistance of AlN microwires and UV resistance of silica fibers, the proposed device is expected to have the good stability and potential applications in the fields of the solar physics and space exploration.

Kinetic Alfvén solitary waves in a low-β plasma with regularized kappa-distributed electrons

This study examines the characteristics of small-amplitude kinetic Alfvén waves (KAWs) in a typical magnetoplasma, where both ions and electrons are considered to have a regularized kappa distribution (RKD). The restrictions imposed on the standard Kappa distribution function will be removed by considering the RKD function. The RKD can also be used for kappa areas for spectral index κ &amp;lt; 3/2. We then use the Korteweg–de Vries equation to investigate the KAWs in this model, which we obtained from the reductive perturbation method. It is observed that the equation’s nonlinear and dispersive coefficients are functions of the Kummar functions and the cut-off parameter. It is found that the nonlinear and dispersive coefficients of this equation depend on the Kummar functions and the cut-off parameter. Due to the negativity of the coefficients of the wave equation, only compressive KAWs can exist and propagate in this model. The numerical results demonstrate a positive correlation between the soliton’s profile (amplitude and width) with an increase in the cut-off parameter. Conversely, the superthermality has a negative influence on the soliton profile. The influence of the soliton’s propagation angle on the magnetic field’s direction is investigated. It is found that the solitary wave will not propagate in the ambient when the propagation angle θ becomes 0 or 90. Overall, the results obtained from this research can be used in space and laboratory plasmas with low β that have non-Maxwellian electrons.

On the arbitrary amplitude ion-acoustic structures in an anisotropic non-Maxwellian electron–positron–ion magnetoplasma

This paper comprehensively investigates the oblique propagation of ion-acoustic solitary waves (IASWs) with arbitrary amplitude in a magnetoplasma consisting of inertialess non-Maxwellian (nonthermal) electrons, inertialess Maxwellian positrons, and inertial adiabatically heated ions. It is postulated that the positive ions demonstrate adiabatic behavior that is distinguished by anisotropic thermal pressure. The study utilizes Sagdeev's pseudopotential theory to analyze the fluid equations of the plasma model and reduce them to the energy equation. Different plasma configuration factors, such as nonthermal parameters, positron concentration, and parallel and perpendicular ion pressure, are being studied to see how they affect the properties of solitary waves with large amplitudes. The findings demonstrate the simultaneous coexistence of compressive and rarefactive IASWs, significantly influenced by positrons and nonthermal electron parameters. The study provides valuable insights into wave phenomena in magnetized plasmas and presents possible applications in both Space and laboratory plasma environments.

To the theory of turbulent dynamo in magnetised weakly compressible astro-geophysical objects

We discuss a phenomenological self-consistent model of a turbulent magnetized conducting fluid for mean flow and magnetic field in geophysical and astrophysical contexts. This model is designed to study spirality and dynamo effect in the study of astro-geophysical magnetic fields. It is believed that the very existence of cosmic magnetic fields is largely explained by the chirality of background turbulence, the simplest measure of which is the non-vanishing helicity of small-scale turbulence. The mean velocity and magnetic fields are modelled using averaged MHD -equations and phenomenological differential equations for the four bulk turbulence quantities (hydro magnetic turbulent energy, magnetic and cross helicity and residual helicity). These model equations, combined with the mean-field equations, allow the most complete construction of a self-consistent model of the turbulent dynamo. These problems and open questions are considered, especially those concerning the model transport equations for the determination of the alpha effect in astrophysical magnetic fields. The presented work is mainly aimed at modelling rotation effects in hydro magnetic turbulent flows of spiral space and thermonuclear plasma.