Dust-plasma Interactions Research Articles

Payload concepts for investigations of electrostatic dust motion on the lunar surface

Significant experimental and computational investigations have explored the feasibility of electrostatically-motivated dust motion on the lunar surface. The motion of lunar dust influences our understanding of the evolution of the surface and may also present a hazard to future exploration vehicles and astronauts. The possibility of a sustained exploration presence on the lunar surface opens the door to long-term experiments on the lunar surface, akin to the science facilities on the International Space Station. We have identified four measurements/observations that would significantly advance our understanding of dust-plasma interactions on the lunar surface. In this context, we provide conceptual designs for payloads to obtain these observations: a Langmuir probe, dust deposit witness plate, regolith charge measurement instrument, and cameras to look for evidence of horizon glow. These payloads could deploy independently and sequentially, or together as a suite. The proposed payloads would provide key observations that would inform future modeling efforts and direct future in situ experiments to understand the dust-plasma environment, both for planetary science and spacecraft design applications.

On the potential variation of charged dust in Saturn's magnetosphere: The dust-plasma interaction

We presented a theory describing interaction between cold plasma and dust grain based on Cassini observations of Enceladus in Saturn's E ring. We assumed a finite-sized dust cloud with inside plasma to simulate the environment. The dust cloud that results from this scenario has a different potential than the surrounding plasma. Cassini's observations revealed the cold plasma characteristics of the Enceladus plume, which include a high plasma density for both electrons and ions at sufficient low temperature. Therefore, the electron fluid is incorporated in the cloud to form a quantum electron gas governed through Fermi-Dirac statistics. According to observations, more electrons bound to the dust grain results in a collective dust plasma interaction with surrounding cold plasma. Dust-plasma interaction predominantly occurred at negative sub-micrometer sized dust grain. • Using Cassini observations of Enceladus in Saturn's E ring as a groundwork, a theory is presented in this article. • The Enceladus plume has cold plasma characteristics. We considered ions as Boltzmannian distributed particles and Fermi-Dirac distribution is applicable for electrons. • We derived relations for the potential variation in the Enceladus plume region and the E-rings. We found that more electrons bound to the dust grain results in a collective dust plasma interaction. • Analytical analysis and the numerical results form the expressions for the given environment is presented.

Neutral beam driven ion cyclotron instability of lower hybrid wave in a tokamak plasma

The effect of dust grains on the parametric coupling of neutral beam driven ion–cyclotron wave instability with a lower hybrid pump wave is studied. A high amplitude lower hybrid pump, which is launched into a tokamak for heating purposes in the presence of neutral beam driven ion-cyclotron waves, can excite the parametric coupling involving two lower hybrid sidebands. In a tokamak, the lower hybrid waves result in parametric excitation of the ion-cyclotron mode and quasi-modes near the edge when the electron oscillatory velocity is greater than the sound velocity. This parametric coupling increases the growth rate of instability when the lower sideband wave is resonant. Moreover, the presence of dust grains in the tokamak plasma, their radius, and the number density significantly affect the growth rate of the instability, which in turn can affect the advanced stage operations of a tokamak. The growth rate of parametric instability scales with the amplitude of the pump wave. The growth rate is found to be linearly increased with the dust grain density, but it decreased with increasing size of dust grains, which means large sized dust grains stabilize the instability. The theoretical results explained in the present paper are very helpful in explaining the complexity in the plasma properties of a tokamak due to the dust–plasma interactions, which can diminish the performance of the International Thermonuclear Experimental Reactor due to potential safety issues.

Effect of dust grains on the parametric coupling of a lower hybrid wave driven ion cyclotron wave in a tokamak plasma

In this article, the effect of dust charge fluctuations on the parametric upconversion of a lower hybrid wave into an ion cyclotron wave and a side band wave in a two-ion species tokamak plasma is studied. When the oscillatory velocity of plasma electrons is a few percent of the sound velocity, the lower hybrid wave becomes unstable and decays into two modes: an ion cyclotron wave mode and a low frequency lower hybrid side band wave. Furthermore, a ponderomotive force by a lower hybrid pump and a side band wave is exerted on the existing electrons, which drives the ion cyclotron decay mode. The presence of negatively charged dust grains and their shape, size, radius, and density influence the instability. The growth rate of instability is calculated by considering typical existing D–T (Deuterium–Tritium) dusty plasma parameters, and it is observed that the growth rate increases with the relative density of dust grains, number density of dust grains, oscillatory velocity of electrons, and amplitude of pump waves. However, the normalized growth rate increases with the unstable wave frequency, and it also increases as we increase the ratio of deuterium to tritium density. Here, the growth rate decreases with the increase in the size of dust grains and electron cyclotron frequency. The theoretical results summarized in the present study are able to efficiently elaborate the complexity produced in plasma properties in a tokamak due to the dust–plasma interactions, which are briefly discussed here.

Modelling of dust generation, transport and remobilization in full-metal fusion reactors

The design, licensing and operation of magnetic confinement fusion reactors impose various limitations on the amount of metallic dust particles residing inside the plasma chamber. In this context, predictive studies of dust production and migration constitute one of the main sources of relevant data. These are mainly conducted using dust transport codes, which rely on coupled dust-plasma and dust-wall interaction models, and require external input on the dust and droplet initial conditions. Some particularities of dust modelling in reactor-relevant conditions are analyzed with an emphasis on dust generation mechanisms relevant for disruption scenarios and on dust remobilization mechanisms relevant for ramp-up scenarios. Emerging topics such as dust production by runaway electron impact and pre-plasma remobilization of magnetic dust are also discussed.

Effect of ionization waves on dust chain formation in a DC discharge

An interesting aspect of complex plasma is its ability to self-organize into a variety of structural configurations and undergo transitions between these states. A striking phenomenon is the isotropic-to-string transition observed in electrorheological complex plasma under the influence of a symmetric ion wake field. Such transitions have been investigated using the Plasma Kristall-4 (PK-4) microgravity laboratory on the International Space Station. Recent experiments and numerical simulations have shown that, under PK-4-relevant discharge conditions, the seemingly homogeneous direct current discharge column is highly inhomogeneous, with large axial electric field oscillations associated with ionization waves occurring on microsecond time scales. A multi-scale numerical model of the dust–plasma interactions is employed to investigate the role of the electric field in the charge of individual dust grains, the ion wake field and the order of string-like structures. Results are compared with those for dust strings formed in similar conditions in the PK-4 experiment.

Physical aspects of dust–plasma interactions

AbstractLow‐pressure gas discharge plasmas are known to be strongly affected by the presence of small dust particles. This issue plays a role in the investigations of dust particle‐forming plasmas, where the dust‐induced instabilities may affect the properties of synthesized dust particles. Also, gas discharges with large amounts of microparticles are used in microgravity experiments, where strongly coupled subsystems of charged microparticles represent particle‐resolved models of liquids and solids. In this field, deep understanding of dust–plasma interactions is required to construct the discharge configurations which would be able to model the desired generic condensed matter physics as well as, in the interpretation of experiments, to distinguish the plasma phenomena from the generic condensed matter physics phenomena. In this review, we address only physical aspects of dust–plasma interactions, that is, we always imply constant chemical composition of the plasma as well as constant size of the dust particles. We also restrict the review to two discharge types: dc discharge and capacitively coupled rf discharge. We describe the experimental methods used in the investigations of dust–plasma interactions and show the approaches to numerical modelling of the gas discharge plasmas with large amounts of dust. Starting from the basic physical principles governing the dust–plasma interactions, we discuss the state‐of‐the‐art understanding of such complicated, discharge‐type‐specific phenomena as dust‐induced stratification and transverse instability in a dc discharge or void formation and heartbeat instability in an rf discharge.

The new physics of dust in plasmas

The new physics of dust, which arises due to dust-plasma interaction in space environments and laboratory devices, is presented. The new research horizons (different new fields of physics involving many challenging research problems and open issues) introduced by this new physics of dust in plasmas are explained. The basic features of dust-plasma interaction, particularly, basic characteristics of dust in plasmas, and typical dusty plasma parameters for different space and laboratory conditions are presented. The complexity and the diversity of the field of the new physics of dust in plasmas are briefly discussed. The theoretical and experimental discoveries of dust associated linear waves, nonlinear structures, and some other important phenomena are mentioned. The basic features of dust associated nonlinear structures (viz. solitary waves, shock structures, and Mach cones) obtained from our recent published works are briefly discussed.

Radar studies of ionospheric dusty plasma phenomena

We discuss the influence of charged dust on radar observations in the Earth ionosphere. This region in the upper Earth atmosphere can be described as a partially ionized, low‐temperature plasma. Plasma parameters vary by orders of magnitude spatially and in time. Dust particles influence the charge balance, in some cases dusty plasma condition is met. The polar mesospheric echoes are an example of dust plasma interactions observed with radar. The mesosphere is a region where atmospheric temperature decreases with altitude and can reach frost point temperature. The formation of the polar mesospheric radar echoes involves neutral atmosphere dynamics, which is latitude dependent and it involves charged dust particles, especially icy dust that forms in the polar summer mesosphere. Charged dust can also influence incoherent scatter that results from electromagnetic waves scattering off electrons, where the electrons are coupled to other charged components. Observers rarely report charged dust signatures in the incoherent scatter spectra; we show that there is a good chance for doing so with improved observations. The incoherent scatter can possibly also be used to estimate the amount of charged dust in the direct vicinity of a meteor, as we show based on the order of magnitude considerations. This prospect of new observational results makes theoretical investigations of radio‐wave scattering in the presence of charged dust with size distributions worthwhile.

A treecode to simulate dust–plasma interactions**Substantial portions of this paper are adapted from chapters 4 and 5 of the first author’s recent PhD dissertation.

The interaction of a small object with surrounding plasma is an area of plasma-physics research with a multitude of applications. This paper introduces the plasma octree code pot, a microscopic simulator of a spheroidal dust grain in a plasma. pot uses the Barnes–Hut treecode algorithm to perform N-body simulations of electrons and ions in the vicinity of a chargeable spheroid, employing also the Boris particle-motion integrator and Hutchinson’s reinjection algorithm from SCEPTIC; a description of the implementation of all three algorithms is provided. We present results from pot simulations of the charging of spheres in magnetised plasmas, and of spheroids in unmagnetized plasmas. The results call into question the validity of using the Boltzmann relation in hybrid PIC codes.

Plasma dynamics in Saturn's middle-latitude ionosphere and implications for magnetosphere-ionosphere coupling

A multifluid model is used to investigate how Saturn's magnetosphere affects ionosphere. The model includes a magnetospheric plasma temperature of 2eV as a boundary condition. The main results are: (1) H+ ions are accelerated along magnetic field lines by ambipolar electric fields and centrifugal force, and have an upward velocity of about 10km/s at 8000km; (2) the ionospheric plasma temperature is 10,000K at 5000km, and is significantly affected by magnetospheric heat flow at high altitudes; (3) modeled electron densities agree with densities from occultation observations if the maximum neutral temperature at a latitude of 54˚ is about 900K or if electrons are heated near an altitude of 2500km; (4) electron heating rates from photoelectrons (≈100K/s) can also give agreement with observed electron densities when the maximum neutral temperature is lower than 700K (note that Cassini observations give 520K); and (5) the ion temperature is high at altitudes above 4000km and is almost the same as the electron temperature. The ionospheric height-integrated Pedersen conductivity, which affects the magnetospheric plasma velocity, varies with local time with values between 0.4 and 10S. We suggest that the sub-corotating ion velocity in the inner magnetosphere depends on the local time, because the conductivity generated by dust–plasma interactions in the inner magnetosphere is almost comparable to the ionospheric conductivity. This indicates that magnetosphere–ionosphere coupling is highly important in the Saturn system.

Dust–wall and dust–plasma interaction in the MIGRAINe code

The physical models implemented in the recently developed dust dynamics code MIGRAINe are described. A major update of the treatment of secondary electron emission, stemming from models adapted to typical scrape-off layer temperatures, is reported. Sputtering and plasma species backscattering are introduced from fits of available experimental data and their relative importance to dust charging and heating is assessed in fusion-relevant scenarios. Moreover, the description of collisions between dust particles and plasma-facing components, based on the approximation of elastic-perfectly plastic adhesive spheres, has been upgraded to take into account the effects of particle size and temperature.

Floating potential of large dust grains with electron emission

Electron emission from the surface of solid particles plays an important role in many dusty plasma phenomena and applications. Examples of such cases include fusion plasmas and dusty plasma systems in our solar system. Electron emission complicates the physics of the plasma-dust interaction. One of the most important aspects of the physics of the dust plasma interaction is the calculation of the particle's floating potential. This is the potential a dust particle acquires when it is in contact with a plasma and it plays a very important role for determining its dynamical behaviour. The orbital motion limited (OML) approach is used in most cases in the literature to model the dust charging physics. However, this approach has severe limitations when the size of the particles is larger than the electron Debye length λDe. Addressing this shortcoming for cases without electron emission, a modified version of OML (MOML) was developed for modelling the charging physics of dust grains larger than the electron Debye length. In this work, we will focus on extending MOML in cases where the particles emit electrons. Furthermore, a general method for calculating the floating potential of dust particles with electron emission will be presented for a range of grain sizes.

On vapor shielding of dust grains of iron, molybdenum, and tungsten in fusion plasmas

The shielding effects of ablation cloud around a small dust grain composed of iron, molybdenum, or tungsten in fusion plasmas are considered. These include collisional dissipation of momentum flux of impinging plasma ions, heat transfer by secondary plasma created due to electron impact ionization of the ablated atoms, and radiative plasma power losses in the ablation cloud. The maximum radius, which limits applicability of existing dust-plasma interaction models neglecting the cloud shielding effects, for dust grains of the considered high-Z metals is calculated as function of plasma parameters. The thermal bifurcation triggered by thermionic electron emission from dust grains, observed for some of the considered materials, is analyzed. The results are compared with previous calculations for dust composed of low-Z fusion related materials, i.e., lithium, beryllium, and carbon.

Migration of tungsten dust in tokamaks: role of dust–wall collisions

The modelling of a controlled tungsten dust injection experiment in TEXTOR by the dust dynamics code MIGRAINe is reported. The code, in addition to the standard dust–plasma interaction processes, also encompasses major mechanical aspects of dust–surface collisions. The use of analytical expressions for the restitution coefficients as functions of the dust radius and impact velocity allows us to account for the sticking and rebound phenomena that define which parts of the dust size distribution can migrate efficiently. The experiment provided unambiguous evidence of long-distance dust migration; artificially introduced tungsten dust particles were collected 120° toroidally away from the injection point, but also a selectivity in the permissible size of transported grains was observed. The main experimental results are reproduced by modelling.

Guest Editorial Special Issue on Dusty Plasmas

This special issue contains papers solicited at the 13th Workshop on the Physics of Dusty Plasmas held May 20-23 in Waco, TX, USA and follows the tradition of earlier workshops, which resulted in such issues in 1994, 2001, 2004, 2007, and 2010. Dusty plasmas constitute a fully developed interdisciplinary field with direct connections to astrophysics, nanoscience, fluid mechanics, and material science as defined through experimental, theoretical, and numerical studies. The field achieved an interdisciplinary research focus when the 1986 fly by of Halley's Comet and Voyager's images of Saturn's rings focused the attention of plasma physicists on a field that had previously been considered as purely planetary science. Joint efforts between these disciplines quickly led to rapid advancement in both plasma physics (e.g., discovery of dustacoustic waves, dust-ion-acoustic waves) and the planetary sciences (e.g., spokes in Saturn's rings, Jovian stream particles). The primary objectives of the 13th Workshop on the Physics of Dusty Plasmas were to provide a review of recent advancements in the field of complex plasma, define new/existing/outstanding issues and research challenges, and strengthen engagement between the field of complex plasma and other research related disciplines. Researchers from universities all over the world, including twenty-six graduate students evenly split between universities in the United States and international universities, participated in the workshop. Eighty-six paper and poster presentations were accepted covering topics including laboratory, theoretical, and computational studies of dust plasma interactions. Sixteen papers from the Waco meeting appear in this special issue covering topics across a variety of theoretical and experimental areas. Instabilities in dusty plasma systems, the manner in which such instabilities are believed to be linked to the onset of dust density or dust-acoustic waves and the mechanism by which these waves evolve and are related to the ambient plasma are reported. Dust dynamics, mass loss, and a method for employing the plasma glow to probe the plasma sheath in the vertical direction are discussed. A numerical method allowing calculation of the grain charge while including secondary electron emission and the application of this method to the lunar environment is provided. Finally techniques for stereoscopic observations, three-dimensional models of dust plasma interactions and dusty plasma experiments allowing inspection of magnetized dusty plasmas and dusty plasma environments containing chemically reactive gases are reported.

Dust Plasma Effect on the Etching Process of Si[100] by Ultra Low Frequency RF Plasma

Dust-plasma interactions play vital roles in numerous observed phenomena in the space environment, their scope in the industrial laboratory has grown rapidly in recent times to include such diverse areas as materials processing, microelectronics, lighting and nuclear fusion. The etching processes of Si wafer has been studied using Ultra low frequency RF plasma (ULFP) at (1 KHz) by two different techniques namely: ion etching using inert gas only (e.g., argon gas), and ion chemical etching using an active gas (beside the inert gas) such as oxygen. In the case of large dust particle, the dust might act as a floating body in the plasma collecting equal fluxes of electrons and ions. The velocity of the ions flux out from the mesh (cathode) and cause ion sputtering for the sample (Si-Wafer) measured, moreover the rate coefficient for collection of electrons and ions by dust (K) is calculated here, the presence of dust, however, may itself cause loss process. As the plasma density increases, the etching rate increases and the volumetric rate of loss of electron and ions due to dust particle increases (K). A comparison between the volumetric rate of loss (K) due to ion chemical etching (75% Ar/25% O2) and ion etching (Pure Ar) has been carried out.

Dust–plasma interaction through magnetosphere–ionosphere coupling in Saturn’s plasma disk

The ion bulk speeds in the equatorial region of Saturn’s inner magnetosphere, according to data from the Langmuir Probe (LP) on board the Cassini spacecraft, are about 60% of the ideal co-rotation speed; the ion speeds are between the co-rotation and Keplerian speeds (Holmberg et al., Ion densities and velocities in the inner plasma torus of Saturn, Planetary and Space Science). These findings suggest that sub-micrometer negatively charged E ring dust contributes to the plasma dynamics in the plasma disk.We calculated the ion speeds by using a multi-species fluid model, taking into account dust interactions to investigate the effects of ion–dust coulomb collision, mass loading, as well as taking into account magnetosphere–ionosphere coupling to investigate the effect of the magnetospheric electric field. The results show that the ion speeds can be significantly reduced by the electric fields generated by the collisions between ions and dusts when the dust density is high and the thickness of dust distribution is large. We also show that the ion speeds from our model are consistent with the LP observations when the maximum density of dust is larger than ∼105m−3.

Modeling of Cassini's charging at Saturn orbit insertion flyby

[1] Spacecraft-plasma interactions are studied in the regime relevant for Cassini during the Saturn orbit insertion (SOI) flyby. Three-dimensional particle-in-cell self-consistent code has been employed to calculate the spacecraft potential in a complicated plasma environment of Saturn's magnetosphere for a wide range of distances (for dipole shells between L ∼ 4 and L ∼ 10). Plasma parameters derived from Cassini plasma spectrometer (CAPS) measurements at the SOI flyby have been used as input data. Modeling includes photoemission due to the solar UV radiation, two populations of ions, plasma flows and the flyby geometry. Numerical results highlight significant differences in the plasma conditions along the SOI trajectory. Outside Rhea's shell, at L ∼ 10, the positive spacecraft potential is primary due to the photoelectron production on the Sun-exposed surface of the orbiter. In the inner plasmasphere (L < 8) the spacecraft charges to a negative potential with values up to a few electron temperatures. The dependence of the potential versus distance from Saturn demonstrates behavior qualitatively similar to that deduced from the CAPS data acquired during the SOI period. Simulations display different spatial structures of the plasma particle densities and the self-consistent potential surrounding the SC at different distances from Saturn. Three plasma constituents (electrons, water group ions and protons) produce a new kind of plasma wake with a self-consistent separation between the plasma components in the electric field of the orbiter. Ion focusing occurs in the inner magnetosphere only for protons while the heavy water group ions always form a geometric wake downstream of the spacecraft. The main factor defining the spatial configurations of the potential and of the plasma density perturbations is the energy distribution of the surrounding plasmas. The obtained results can be of importance for understanding the main physical processes occurring in Saturn's magnetosphere, including dust-plasma interactions in the planetary rings, and for reliable interpretations of the electric field and plasma parameter measurements.

Dusty Plasma Effects in Near Earth Space and Interplanetary Medium

We review dust and meteoroid fluxes and their dusty plasma effects in the interplanetary medium near Earth orbit and in the Earth’s ionosphere. Aside from in-situ measurements from sounding rockets and spacecraft, experimental data cover radar and optical observations of meteors. Dust plasma interactions in the interplanetary medium are observed by the detection of charged dust particles, by the detection of dust that is accelerated in the solar wind and by the detection of ions and neutrals that are released from the dust. These interactions are not well understood and lack quantitative description. There is still a huge discrepancy in the estimates of meteoroid mass deposition into the atmosphere. The radar meteor observations are of particular interest for determining this number. Dust measurements from spacecraft require a better understanding of the dust impact ionization process, as well as of the dust charging processes. The latter are also important for further studying nanodust trajectories in the solar wind. Moreover understanding of the complex dependencies that cause the variation of nanodust fluxes is still a challenge.