Abstract:Abstract-Planetary formation is an efficient process now thought to take place on a relatively short astronomical time scale. Recent observations have shown that the dust surrounding a protostar emits more efficiently at longer wavelengths as the protoplanetary disk evolves, suggesting that the dust particles are coagulating into fluffy aggregates, "much as dust bunnies form under a bed."One poorly understood problem in this coagulation process is the manner in which micron-sized, charged grains form the fract… Show more
“…The electrostatic charge and dipole moment of individual particles in a cloud of spherical dielectric particles, dispersed in air passing through a non-uniform electric field, has been experimentally measured in [31] by studying the particles' trajectories. In numerical studies, the electric charge and dipole moment of aggregates in a plasma environment has been calculated using modified OM L theory [32] and the interaction between two charged grains modeled by calculating the torques and accelerations due to the charged aggregates or external electric fields [23,33]. However a direct study of both electrostatic charge and dipole of dust particles in laboratory plasmas has not yet been made.…”
Understanding the agglomeration of dust particles in complex plasmas requires a knowledge of the basic properties such as the net electrostatic charge and dipole moment of the dust. In this study, dust aggregates are formed from gold coated mono-disperse spherical melamine-formaldehyde monomers in a radio-frequency (rf) argon discharge plasma. The behavior of observed dust aggregates is analyzed both by studying the particle trajectories and by employing computer models examining 3D structures of aggregates and their interactions and rotations as induced by torques arising from their dipole moments. These allow the basic characteristics of the dust aggregates, such as the electrostatic charge and dipole moment, to be determined. It is shown that the experimental results support the predicted values from computer models for aggregates in these environments.
“…The electrostatic charge and dipole moment of individual particles in a cloud of spherical dielectric particles, dispersed in air passing through a non-uniform electric field, has been experimentally measured in [31] by studying the particles' trajectories. In numerical studies, the electric charge and dipole moment of aggregates in a plasma environment has been calculated using modified OM L theory [32] and the interaction between two charged grains modeled by calculating the torques and accelerations due to the charged aggregates or external electric fields [23,33]. However a direct study of both electrostatic charge and dipole of dust particles in laboratory plasmas has not yet been made.…”
Understanding the agglomeration of dust particles in complex plasmas requires a knowledge of the basic properties such as the net electrostatic charge and dipole moment of the dust. In this study, dust aggregates are formed from gold coated mono-disperse spherical melamine-formaldehyde monomers in a radio-frequency (rf) argon discharge plasma. The behavior of observed dust aggregates is analyzed both by studying the particle trajectories and by employing computer models examining 3D structures of aggregates and their interactions and rotations as induced by torques arising from their dipole moments. These allow the basic characteristics of the dust aggregates, such as the electrostatic charge and dipole moment, to be determined. It is shown that the experimental results support the predicted values from computer models for aggregates in these environments.
“…In this study, aggregates were created by numerically modeling the interactions between colliding particle pairs [11]. Working in the center of mass (COM) frame of an initial seed particle, a second monomer or aggregate was chosen to approach this particle from a random direction.…”
Section: Methodsmentioning
confidence: 99%
“…The charge on an aggregate is approximated using both the monopole and dipole moments [11], while the magnetic dipole moment is calculated as the vector sum of the dipole moments of the individual monomers. …”
Abstract-The interaction between dust grains is an important process in fields as diverse as planetesimal formation or the plasma processing of silicon wafers into computer chips. This interaction depends in large part on the material properties of the grains, for example whether the grains are conducting, nonconducting, ferrous or non-ferrous. This work considers the effects that electrostatic and magnetic forces, alone or in combination, can have on the coagulation of dust in various environments. A numerical model is used to simulate the coagulation of charged, charged-magnetic and magnetic dust aggregates formed from ferrous material and the results are compared to each other as well as to those from uncharged, nonmagnetic material. The interactions between extended dust aggregates are also examined, specifically looking at how the arrangement of charge over the aggregate surface or the inclusion of magnetic material produces dipole-dipole interactions. It will be shown that these dipole-dipole interactions can affect the orientation and structural formation of aggregates as they collide and stick. Analysis of the resulting dust populations will also demonstrate the impact that grain composition and/or charge can have on the structure of the aggregate as characterized by the resulting fractal dimension.
“…Charging effects are usually considered to be insignificant, or are merely mentioned as an after-thought (Blum & Wurm 2008). Recently, simulations have shown that the effect of even a very modest grain charge can not be neglected; as such, a self-consistent charging/coagulation approach for plasma environments relevant to PPDs seems to now be in order (Matthews et al 2007;Okuzumi 2009). Recent experiments have also provided evidence for run-away growth induced by electrostatic dipole interactions, showing that charging of particles can in fact speed up the coagulation processes (Konopka et al 2005), as was also shown numerically (Matthews & Hyde 2009).…”
Section: The Formation Of Planetsmentioning
confidence: 99%
“…The code has since been modified and extended to include the effects of charged particles and magnetic fields (Matthews & Hyde 2003;Vasut & Hyde 2001;Qiao et al 2007). The modified code treats accelerations caused by interactions of charged grains as well as rotations induced by torques due to the charge dipole moments (Matthews et al 2007). These dipole-dipole interactions have been shown to greatly enhance the collision rate, even for like-charged particles (Matthews & Hyde 2009).…”
Combining a particle-particle, particle-cluster and cluster-cluster agglomeration model with an aggregate charging model, the coagulation and charging of dust particles in various plasma environments relevant for proto-planetary disks have been investigated. The results show that charged aggregates tend to grow by adding small particles and clusters to larger particles and clusters, leading to greater sizes and masses as compared to neutral aggregates, for the same number of monomers in the aggregate. In addition, aggregates coagulating in a Lorentzian plasma (containing a larger fraction of high-energy plasma particles) are more massive and larger than aggregates coagulating in a Maxwellian plasma, for the same plasma densities and characteristic temperature. Comparisons of the grain structure, utilizing the compactness factor, φ σ , demonstrate that a Lorentzian plasma environment results in fluffier aggregates, with small φ σ , which exhibit a narrow compactness factor distribution. Neutral aggregates are more compact, with larger φ σ , and exhibit a larger variation in fluffiness. Measurement of the compactness factor of large populations of aggregates is shown to provide information on the disk parameters that were present during aggregation.Subject headings: accretion disk -dust -planets and satellites: formation -plasmasprotoplanetary disks
The formation of planetsAt the time of writing more than 500 exoplanets have been observed with more than 400 of these confirmed, and more planets are being detected and confirmed on a weekly basis 1 . Even though these discoveries show that the process of planet formation is in itself a general one, they have also shown that our Solar System is everything but the perfect example of the average planetary system, Pluto, or no Pluto. Partly due to the inherent bias of the available observational techniques, many of the earliest discovered systems involved large gaseous planets orbiting close to the parent star and planets on very eccentric orbits, much in contrast with our Solar System (Ollivier et al. 2009). Since many early planet formation theories were based on the Solar System (and in many cases these were then tested against our Solar System), these observations make clear that our knowledge of planet formation is incomplete.The environment in which planet formation takes place is generally accepted to be a proto-planetary disk (PPD), a disk of gas and small (nanometer to millimeter sized) dust particulates accreting matter onto the central young stellar object (YSO), a famous 1 1http://www.exoplanets.org, http://www.exoplanet.eu
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.