Plasma Cloud Research Articles

Dynamics of a Plasma Cloud Generated by a Compact Coaxial Gun upon Expansion into Vacuum and Large-Volume Background Plasma in an External Magnetic Field

Dynamics of a Plasma Cloud Generated by a Compact Coaxial Gun upon Expansion into Vacuum and Large-Volume Background Plasma in an External Magnetic Field

Influence of a Secondary Plasma Cloud on the Ablation of Pellets in Magnetic Confinement Devices

Influence of a Secondary Plasma Cloud on the Ablation of Pellets in Magnetic Confinement Devices

Plasmasphere Control of ULF Wave Distribution at Different Geomagnetic Conditions

AbstractMagnetic storms and substorms cause global disturbances in the Earth's magnetosphere. Plasma clouds injected from the magnetotail during storm or substorm drift around the Earth and generate ultra‐low frequency (ULF) waves via various mechanisms. At the same time, the inner part of the magnetosphere called plasmasphere is filled with cold particles and its characteristics are sensitive to the geomagnetic activity level. Previous theoretical and some observational studies suggested plasmasphere and its boundary, plasmapause, are special regions for ULF waves to interact with charged particles. We present a statistical analysis of ULF waves during different geomagnetic conditions. We utilized Arase satellite magnetic field and electron density measurements from March 2017 to December 2020 to investigate spatial distribution of ULF waves and its dependence on the plasmapause location. A 1–2 RE gap between the plasmapause and a region of high transverse waves occurrence rate was found. This gap keeps during quiet geomagnetic conditions when plasmasphere expands, and we concluded that the plasmapause controls the ULF wave distribution in the magnetosphere. ULF wave occurrence rate significantly decreases at quiet time, but dayside and dawnside maxima still occur for poloidal and compressional, and toroidal waves, respectively. Thus, we can distinguish internally and externally excited waves. Average wave frequency distribution revealed field‐line resonance character of toroidal waves as frequency increases toward the Earth. Poloidal and compressional waves distributions clearly distinguish low frequency externally excited waves and high frequency storm‐time pulsations.

Local Electron Density Depletions in the Martian Upper Ionosphere Obtained From MARSIS: Comparison With ASPERA‐3, and MAVEN, and the Connection With Crustal Magnetic Fields

AbstractSteep electron density depletions in the Martian ionosphere are important, especially because they could be regions of significant plasma escape. Local electron density profiles of the Martian ionosphere obtained from the radar sounder onboard the Mars Express spacecraft often show large fluctuations. In some cases, these fluctuations are observed as deep depletions in the electron density. Investigation over the past 12 years of Mars Advanced Radar for Subsurface and Ionospheric Sounding data have revealed over 200 cases of density depletions where the lowest density is less than one fifth of the density in the surrounding regions. These density dips occur both on the dayside and the nightside, with an abundance between solar zenith angles of 50–70° and 100–120°. They occur at all altitudes in the ionosphere. Many of the depletions occur in the southern hemisphere where the crustal magnetic field is stronger and there are more regions where the crustal magnetic field is mostly vertical. In more than half of the cases, the depletion in the local electron density corresponds to a decrease in the electron flux measured with the Analyzer of Space Plasmas and Energetic Atoms electron spectrometer. Several different mechanisms could be responsible for the formation of the depletions, including regions of localized electric fields or magnetic fields creating areas of increased field pressure, escape of the plasma along magnetic field lines depleting density locally, and the density decrease around the photoelectron boundary followed by an increase in the plasma density due to plasma clouds.

Relativistic Magnetic Reconnection in Colliding Plasma Clouds Generated by Multiple High Power Laser Pulses

Relativistic Magnetic Reconnection in Colliding Plasma Clouds Generated by Multiple High Power Laser Pulses

Interaction of the Substance of the Tsarev Meteorite with Radiation from a Powerful Gyrotron: Dusty Plasma Cloud Formation and Phase Transformations

A new approach for simulation of the interaction of space and lunar dust with the surface of spacecrafts has been proposed. The approach is based on creating a dusty plasma cloud when the substance imitating the space or lunar dust is treated with high-power pulsed microwave radiation in the developed experimental facility. The facility consists of a high-power gyrotron (75 GHz, 0.8 MW); a plasma-chemical reactor; and a diagnostic complex, which includes optical emission spectrometers and a high-speed camera. The approach has been tested using the substance of the Tsarev meteorite, which represents a typical substance of meteorites. It was found that the substance mainly keeps the phase composition; however, the particles change their morphology due to rapid heating and melting.

Meterwavelength Single Pulse Polarimetric Emission Survey. VI. Toward Understanding the Phenomenon of Pulsar Polarization in Partially Screened Vacuum Gap Model

We have observed 123 pulsars with periods longer than 0.1 s in the Meterwavelength Single Pulse Polarimetric Emission Survey. In this work, a detailed study of the polarization behavior of these pulsars has been carried out. We were able to fit the rotating vector model to the polarization position angle sweeps in 68 pulsars, and in 34 pulsars the emission heights could be measured. In all cases the radio emission was constrained to arise below 10% of the light cylinder radius. In pulsars with low spin-down energy loss, erg s−1, we found the mean fractional linear polarization of the individual time samples in single pulses to be around 0.57 (57%), which is significantly larger than the fractional linear polarization of 0.29 (29%) obtained from the average profiles. On the other hand, the mean fractional circular polarization of the individual time samples in single pulses is around 0.08 (8%), similar to the measurements from the average profiles. To explain the observed polarization features, we invoke the partially screened vacuum gap model of pulsars, where dense spark-associated plasma clouds exist with high pair plasma multiplicity, with significant decrease of density in the regions between the clouds that are dominated by iron ions. The coherent radio emission is excited by curvature radiation from charge bunches in these dense plasma clouds and escape as linearly polarized waves near cloud boundaries. We suggest that the circular polarization arises due to propagation of waves in the low-pair-multiplicity, ion-dominated inter-cloud regions.

Study on electrothermal ignition model of self-propagation high-temperature synthesis system for samarium vaporization

The quality of short-wave radio communication in the ionosphere depends largely on the state of the ionosphere, but it is uncontrollable and unreliable. The release of gaseous samarium into the ionospheric space can form high-density plasma clouds, which is of great significance for improving the quality of shortwave radio communication. The high temperature and high heat released by the self-propagation high-temperature synthesis reaction can effectively heat and vaporize the samarium. At the same time, this method can effectively avoid the adverse impact of the reaction of individual components of the reaction material on the ionization efficiency of samarium, and greatly improve the ionization efficiency of the samarium. Therefore, self-propagation high-temperature synthesis is an important method for heating and vaporizing samarium. To study the ignition model of self-propagation high-temperature synthesis system for heating and vaporizing samarium, and to design and control the ignition process is the premise for heating and vaporizing samarium. Based on the theory of chemical reaction and heat conduction, the electrothermal ignition process is studied in detail. By analyzing the change of energy distribution in the ignition process, a theoretical model of ignition under the electric energy heating mode is proposed, and a theoretical equation for calculating the ignition time is derived. The model can be used to design and control the ignition system and explain many phenomena in the ignition process. In addition, the electrothermal ignition test was carried out for heating and vaporizing samarium in the self-propagation high-temperature synthesis system to obtain the ignition power and ignition time of different reaction systems under different samarium content and porosity, and further analyze the universality of the calculation model. The results show that the test results are in good agreement with the theoretical calculation results, and the validity of the model is verified, which provides an important support for the design of self-propagation high-temperature synthesis reaction heating and vaporizing samarium ignition system.

Simulation of cathode spots crater formation on electrodes with micro-scale and nano-scale alloy materials in a vacuum arc

In the field of vacuum interrupting, an important research is to improve the erosion resistance properties of contacts. In this paper, a two-dimensional axisymmetric swirl model based on basic parameters has been proposed to describe the formation and development of cathode spots of micro-scale alloy and nano-scale alloy electrode in a vacuum arc. In this model, the peak ion density of the plasma cloud, the mean charge state in near-cathode region, the electron temperature, and the near-cathode voltage drop are adopted as external parameters. Ions and electrons originating from the plasma cloud, thermo-field (T-F) emission, vaporization of metal atoms, backing ions and back-diffused electrons are all taken into consideration. The morphology and temperature of cathode spots crater and the liquid metal velocity of pure copper electrode (Cu), copper-chromium (Cu-Cr) electrode and tungsten-copper (W-Cu) electrode under the conditions of micro-scale grains and nano-scale grains are compared, respectively. Simulation results show that the cathode spot crater of the Cu-Cr electrode is smaller than that of the pure copper electrode. Moreover, it can hold more current and inhibit the formation of new cathode spots nearby. Cathode spots appearing on tungsten grains are smaller in size and have a lower probability of forming liquid metal droplets than Cu-Cr electrodes. Contacts made of nano-scale grain alloys have stronger erosion resistance properties than that of micro-scale alloy contacts and can reduce the maximum temperature of the cathode. The simulation results are in good agreement with other researchers’ results.

Setting up experiments with laser plasma clouds to simulate the generation of quasi-spherical collisionless shock waves in cosmic plasma, based on calculations by the particle (ion) method using a hybrid model

Setting up experiments with laser plasma clouds to simulate the generation of quasi-spherical collisionless shock waves in cosmic plasma, based on calculations by the particle (ion) method using a hybrid model

Trajectories of coronal mass ejection from solar-type stars

ABSTRACT The Sun and other solar-type stars have magnetic fields that permeate their interior and surface, extend through the interplanetary medium, and are the main drivers of stellar activity. Stellar magnetic activity affects the physical processes and conditions of the interplanetary medium and orbiting planets. Coronal mass ejections (CMEs) are the most impactful of these phenomena in near-Earth space weather and consist of plasma clouds with a magnetic field, ejected from the solar corona. Precisely predicting the trajectory of CMEs is crucial in determining whether a CME will hit a planet and impact its magnetosphere and atmosphere. Despite the rapid developments in the search for stellar CMEs, their detection is still very incipient. In this work, we aim to better understand the propagation of CMEs by analysing the influence of initial parameters on CME trajectories, such as position, velocities, and the stellar magnetic field’s configuration. We reconstruct magnetograms for Kepler-63 (KIC 11554435) and Kepler-411 (KIC 11551692) from spot transit mapping, and use a CME deflection model, ForeCAT, to simulate trajectories of hypothetical CMEs launched into the interplanetary medium from Kepler-63 and Kepler-411. We apply the same methodology to the Sun, for comparison. Our results show that in general deflections and rotations of CMEs decrease with their radial velocity and increase with ejection latitude. Moreover, magnetic fields stronger than the Sun’s, such as Kepler-63’s, tend to cause greater CME deflections.

Magnetic field of solar dark filaments obtained from He i10830 Å spectropolarimetric observation

AbstractSolar filaments are dense, cool plasma clouds in the solar corona. They are supposed to be supported in a dip of the coronal magnetic field. However, the models still disagree between two types of field configuration; one is the normal polarity model proposed by Kippenhahn and Schlueter (1957, Z. Astrophys., 43, 36), and the other is the reverse polarity model proposed by Kuperus and Raadu (1974, A&A, 31, 189). To understand the mechanism that makes the filaments become unstable before eruption, it is critical to know the magnetic structure of solar filaments. We performed spectropolarimetric observation in the He i (10830 Å) line to investigate the magnetic field configuration of dark filaments. The observation was carried out with the Domeless Solar Telescope at Hida Observatory with a polarization sensitivity of 3.0 × 10−4. We obtained eight samples of filaments in a quiet region. As a result of the analysis of full Stokes profiles of filaments, we found that the field strengths were estimated as 8–35 G. By comparing the direction of the magnetic field in filaments and the global distribution of the photospheric magnetic field, we determined the magnetic field configuration of the filaments, and we concluded that one out of the eight samples has normal polarity configuration, and seven out of the eight have reverse polarity configuration.

Nonlinear Three-Dimensional Simulations of the Gradient Drift and Secondary Kelvin–Helmholtz Instabilities in Ionospheric Plasma Clouds

A newly developed three-dimensional electrostatic fluid model solving continuity and current closure equations aims to study phenomena that generate ionospheric turbulence. The model is spatially discretized using a pseudo-spectral method with full Fourier basis functions and evolved in time using a four-stage, fourth-order Runge Kutta method. The 3D numerical model is used here to investigate the behavior and evolution of ionospheric plasma clouds. This problem has historically been used to study the processes governing the evolution of the irregularities in the F region of the ionosphere. It has been shown that these artificial clouds can become unstable and structure rapidly (i.e., cascade to smaller scales transverse to the ambient magnetic field). The primary mechanism which causes this structuring of ionospheric clouds is the E×B, or the gradient drift instability (GDI). The persistence and scale sizes of the resulting structures cannot be fully explained by a two-dimensional model. Therefore, we suggest here that the inclusion of three-dimensional effects is key to a successful interpretation of mid-latitude irregularities, as well as a prerequisite for a credible simulation of these processes. We investigate the results of 2D and 3D nonlinear simulations of the GDI and secondary Kelvin–Helmholtz instability (KHI) in plasma clouds for three different regimes: highly collisional (≈200 km), collisional (≈300 km), and inertial (≈450 km). The inclusion of inertial effects permits the growth of the secondary KHI. For the three different regimes, the overall evolution of structuring of plasma cloud occurs on longer timescales in 3D simulations. The inclusion of three-dimensional effects, in particular, the ambipolar potential in the current closure equation, introduces an azimuthal “twist“ about the axis of the cloud (i.e., the magnetic field B). This azimuthal “twist” is observed in the purely collisional regime, and it causes the perturbations to have a non-flute-like character (k‖≠0). However, for the 3D inertial simulations, the cloud rapidly diffuses to a state in which the sheared azimuthal flow is substantially reduced; subsequently, the cloud becomes unstable and structures, by retaining the flute-like character of the perturbations (k‖=0).

Kelvin–Helmholtz Instability at Mars: In Situ Observations and Kinetic Simulations

Kelvin–Helmholtz (K-H) instability is a fundamental boundary instability between two fluids with different speeds, exchanging the mass, momentum, and energy across the boundary. Although the K-H instability has been suggested to play a critical role in atmospheric ion loss on Mars, the knowledge about its formation and evolution is still poor, due to the limitation of spacecraft missions and a dearth of dedicated simulation codes. In this study, we combine observations from the Mars Atmosphere and Volatile EvolutioN mission and global 3D kinetic simulations to investigate the solar wind–Mars interaction. For the first time, it is found that K-H waves prominently appear in the −E hemisphere, which is attributed to the stronger proton velocity shear therein associated with the asymmetric diamagnetic drift motion of protons. The K-H instability is mainly excited in the −E hemisphere and propagates downstream along the boundary, with the waves also able to be generated near the subsolar point. The K-H waves produce plasma clouds with a net oxygen ion escape rate of about 1.5 × 1024 s−1, contributing to almost half of the global loss on present-day Mars. This heavy ion escape pattern associated with K-H instability is cyclic and could occur on other nonmagnetized planets, potentially influencing planetary atmosphere evolution and habitability.

Variability of Antenna Signals From Dust Impacts

AbstractElectric field instruments carried by spacecraft (SC) are complementary to dedicated dust detectors by registering transient voltage perturbations caused by impact‐generated plasma. The signal waveform contains information about the interaction between the impact‐generated plasma cloud and the elements of SC‐antenna system. The variability of antenna signals from dust impacts has not yet been systematically characterized. A set of laboratory measurements are performed to characterize signal variations in response to SC parameters (bias voltage and antenna configuration) and impactor parameters (impact speed and composition). The measurements demonstrate that dipole antenna configurations are sensitive to dust impacts and that the detected signals vary with impact location. When dust impacts occur at low speeds, the antennas typically register smaller amplitudes and less characteristic impact signal shapes. In this case, impact event identification may be more challenging due to lower signal‐to‐noise ratios and/or more variable waveforms shapes, indicating the compound nature of nonfully developed impact‐generated plasmas. To investigate possible variations in the impacting materials, the measurements are carried out using two dust samples with different mass densities: iron and aluminum. No significant variations of the measured waveform or plasma parameters obtained from data analysis are observed between the two materials used.

On the Formation of Clouds in the Dusty Ionosphere of Mars

Dusty plasma clouds observed at altitudes of about 100 km in the mesosphere of Mars have been considered. Features of the dusty ionosphere of Mars compared to the dusty ionosphere of the Earth have been listed. The equations of the model describing self-consistently dusty plasma structures in the ionosphere of Mars have been presented. This model involves features that are important for the ionosphere of Mars but are ignored when describing the dusty plasma system in the ionosphere of the Earth. In particular, the model for Mars involves effects of deceleration of dust particles because of the adhesion of condensed molecules to them. An altitude distribution of particles constituting mesospheric clouds on Mars has been calculated with the self-consistent model. It has been shown that an important factor for the formation of dusty plasma clouds in the ionosphere of Mars is the Rayleigh–Taylor instability, which limits both the maximum size of dust particles that can form dusty plasma clouds and the maximum thickness of the dusty plasma clouds.

Fine Structures of Type-IV Solar Radio Bursts Associated with Stationary and Moving Sources

Various types of fine structure in the continuum emission of type-IV radio bursts are considered asapplied to different types of radiation sources, both stationary and moving. In the case of stationary sources,the origin of the fine structure is associated both with processes in individual magnetic loops (quasi-periodicacceleration and magnetohydrodynamic waves), and with large-scale processes associated with the propagationof magnetohydrodynamic disturbances, the formation of loop arcades, and processes of discrete accelerationof particles synchronous with them, causing the pulsating nature of radio emissions. For the case of amoving source, the generation mechanism largely depends on the magnetic structure of the source (anexpanding magnetic arc or an isolated plasma cloud). In this case, the connection with coronal mass ejectionsand shock waves is also important. Secondary pulsations are explained by a magnetohydrodynamic fluctuationsource in the form of a magnetic loop or cloud. The absence of other fine structures in the continuum ofmoving type-IV bursts may be due to the critical angle of the loss cone for the excitation of whistlers

Enhanced Performance of Series Microexploding Bridge Planar Discharge Switch Integrated With Exploding Foil

To achieve the low energy, miniaturization, and low cost of the exploding bridge foil initiator, single and series microexploding bridge planar discharge switch (MEB-PDS) coplanar and cocathode integrated with exploding bridge foil is fabricated by magnetron sputtering and photolithography forming etching in this work. The maximum electrostatic field strength and breakdown voltage of the MEB-PDS are calculated by multiphysics field theory. The breakdown voltage, conduction performance, MEB electrical explosion performance, and integrated exploding foil initiator (EFI) of the MEB-PDS have been tested. The relationship between breakdown voltages and design parameters, variation law between conduction time and design parameters, operating voltages and trigger voltages, and the matching between operating voltages and trigger voltages of MEB-PDS are analyzed. The results show that the breakdown voltages of single-bridge and three-series MEB-PDS can meet the insulation requirements at the operating voltage. The plasma clouds generated by the three-series MEB-PDS converge and superimpose, which results in its better conduction performance and operating reliability than single MEB-PDS. Based on the optimization of MEB structure parameters, the breakdown voltage of the three-series MEB-PDS is 2.848 kV at a trigger voltage of 0.600 kV. The 50% ignition voltage sensitivity U (50%) of the corresponding integrated exploding foil initiator is 1.191 kV, and the 99.9% ignition voltage sensitivity U (99.9%) is 1.269 kV. Compared with other types of spark gap discharge switches, U (99.9%) is reduced by 11.07%. The trigger voltage of the switch is reduced from ∼1.5 to 0.6 kV.

Observations and simulations of stellar coronal mass ejections

<p indent="0mm">Coronal mass ejections (CMEs) normally refer to large-scale plasma clouds ejected from the Sun. On other stars, similar phenomena are called stellar coronal mass ejections or stellar CMEs. Based on our current understanding of solar CMEs, it is believed that stellar CMEs are likely the main drivers of space weather in star-exoplanet systems. Thus, as an important factor affecting the surrounding exoplanets, stellar CMEs play a key role in the formation of habitable worlds beyond the solar system. During certain periods of the long evolutionary histories of some stars, frequently occurring stellar CMEs could also significantly contribute to the mass and momentum loss of some stars. However, so far, there has been almost no solid observational evidence of a single stellar CME event, although some stellar CME candidates have been identified from multi-wavelength observations. Here we summarize several proposed methods of stellar CME detection, introduce existing attempts at stellar CME hunting as well as modeling of stellar CMEs and their interactions with exoplanets. We also point out limitations of these attempts and discuss future directions of stellar CME detection and modeling.

On the Formation of a Plasma Cloud at the Ablation of a Pellet in a High-Temperature Magnetized Toroidal Plasma

The investigation of cold secondary plasma clouds near pellets ablating in the hot plasma of magnetic confinement devices (tokamaks and stellarators) provides valuable information on the physical characteristics of a pellet cloud. In this work, the characteristic sizes of emitting clouds around fusible polystyrene pellets and refractory carbon pellets have been analyzed. The calculation of the ionization length of C+ ions in both carbon and hydrocarbon clouds has shown that the contribution of only hot electrons is insufficient to ensure the experimentally observed decay lengths of the CII line intensity. Taking into account the strong shielding of the electron flux of the background plasma in the hydrocarbon pellet cloud, the ionization of C+ ions in this cloud is determined predominantly by electrons of the cold plasma of the cloud. Shielding near a refractory carbon pellet is weak because its ablation rate is lower. The contributions from hot electrons of the surrounding plasma and cold electrons of the pellet cloud to the ionization of C+ ions are comparable in the case of carbon pellets.