Stream Of Particles Research Articles

The Correlation between Solar Wind and Active Sunspot AR2776 in 25th Solar Cycle

The solar wind is one of the main properties of the Sun which has a stream of charged particles released from the corona of the Sun. The study of this parameter has started in 1957 and there are a few models that related to prove how the solar wind could escape from the Sun’s gravity. In this paper, we choose the latest solar event that occurred on 16th October 2020 in this new 25th solar cycle. During these months, the Sun considered as active mode and the active region AR2776 potentially contributes high solar activities. Uniquely, a micro solar flare class B formed together with solar burst type II. A very intense flashing which also known as Ellerman bombs can be detected in the optical region. The sunspot number is only 14 and solar wind exceeds up to 306 kms -1 with a density of 4.0 protons/cm 3. We confirmed that AR2776 is a member of Solar Cycle 25.

Time evolution of stream interaction region energetic particle spectra in the inner heliosphere

We analyze an energetic proton event associated with a stream interaction region (SIR) that was observed at Parker Solar Probe on day 320 of 2018 when the spacecraft was just 0.34 AU from the Sun. Using the Integrated Science Investigation of the Sun instrument suite, we perform a spectral analysis of the event and show how the observed spectra evolve over the course of the event. We find that the spectra from the first day of the event are much more consistent with local acceleration at a weak compression, while spectra from later on are more typical of SIR-related events in which particles accelerated at distant shocks dominate. After the first day, the spectra remain approximately constant, which indicates that the modulation of energetic particles during transit from the presumed source region is weaker than previously thought. We argue that these observations can be explained by a sub-Parker spiral magnetic field structure connecting the spacecraft to a source region in the SIR that is relatively close to the Sun. We further propose that acceleration at weak, pre-shock compressions likely plays an important role in observations of SIR-related events in the inner heliosphere and that future modelling of such events should consider acceleration all along the compression region, not just at the distant shock region.

Data set generation at novel test-rig for validation of numerical models for modeling granular flows

Significant effort has been exerted on developing fast and reliable numerical models for modeling particulate flow; this is challenging owing to the complexity of such flows. To achieve this, reliable and high-quality experimental data are required for model development and validation. This study presents the design of a novel test-rig that allows the visualization and measurement of particle flow patterns during the collision of two particle streams. Valuable data sets are provided for the validation of numerical models dedicated to granular flows. The experimental work was conducted for three particle distributions and different configurations of the test rig setup. Additionally, a standard discrete element method for modeling particle transport was applied to the test-rig configuration and the effects of the material spring constant on the predicated flow patterns are investigated. An additional purpose of these simulations was also to collect necessary data for further collision model validation, developed based on a reduced-order technique.

The spatial density distribution of the ion flux in the laser-plasma source for deposition of nanocoating on substrates of increased size

The present work is devoted to the experimental determination of the uniformity of the ion flux density on a substrate with an increased size (~200 cm2 ) in order to form nanostructures by the laser-plasma method. The system for deposition of nanostructures consists of an erosion laser torch of the target material and a substrate located in a vacuum chamber. For smooth adjustment of the parameters of the deposited particles on the substrate, a grid is located between the laser target and the substrate, on which a negative potential is applied relative to the laser target. As a result, a particle stream is formed after the grid, consisting mainly of ions, whose energy can be reliably and smoothly controlled by applying a positive potential to the grid in relation to the substrate. Experiments have shown that the uniformity of the density of ion fluxes on a substrate of increased size (~200 cm2 ) in a laser-plasma source for nanocoating can be increased by applying an accelerating potential to the substrate in relation to the grid. The minimum difference between the ion flux density in the center of the target and at its edge can be reduced to ~5 %. As a result, it is technologically possible to clean the surface of the substrate with ions of the laser target material (secondary emission), create a pseudodiffusion layer of the target material in the near-surface region of the substrate, and apply the laser target material to the substrate. At the same time, all these operations can be performed sequentially without depressurising the vacuum chamber. This allows obtaining coating with good adhesion on substrates of increased size.

The heating of a stream of particles by thermal counter radiation

Introduction. It is accepted that the depth of heating of the dust/gas/air mixture by the radiation of combustion products SR is equal to the length LR of the free path of radiation in the mixture. Numerical simulation of combustion of a gas-air mixture that has inert particles, taking into account the re-radiation of heat by heated particles of the fresh mixture, led to ratio SR >> LR. In this work, the analytical assessment of ratio χS = SR/LR is performed.One-dimensional problem model. The co-authors determined stationary temperature distribution over the flow of initially cold monodisperse particles suspended in vacuum. Particle velocity V is directed toward a heat-radiating, absolutely black surface that is permeable by particles. Simplifying assumptions are used: radiation consists of two oppositely-directed flows of electromagnetic energy; interaction between particles and radiation is described in the approximation of geometric optics; the temperature inside the particle is the same. Problem solving. It is shown that χS is determined by V=Vcp / (εT 0,5, σTb)3 , where cp, εT, σ, Tb are, respectively, heat capacity per unit volume of the suspended matter, integral emissivity of the particle material, the Stefan-Boltzmann constant, and the surface temperature. For ≤ 2.8, re-emission can be neglected: χS ≈ 1. At ≤ 1.2, temperature distribution regulates re-emission: χS ≈ 5 –1/(2 – εT) >> 1.Solution discussion. The analytical solution satisfactorily describes the available numerical solutions and experimental data for the case of combustion of a dust/gas/air mixture after specifying the parameters of a simplified model: the radiating surface should be understood as the flame front, Tb is the combustion temperature, and cp is the overall heat capacity of the mixture. The estimate ≤ 1.2 indicates the final high temperature of the gas suspension, the possibility of its autoignition far from the flame, and the need to change initial assumptions when simulating re-emission.Conclusions. Analytical evaluations make it possible to employ ratios SR >> LR and SR ≈ LR for the suspension over a thermal radiation source in vacuum. Conditions for the application of the results of simplified simulation of re-emission to the combustion of a dust/gas/air mixture are formulated.

Ernest Rutherford’s ambitions

One of the pioneers of radioactivity research, Rutherford feared his work would be overlooked—and changed his publishing strategies to make sure it wasn’t.

Modelling cometary meteoroid stream traverses of the Martian Moons eXploration (MMX) spacecraft en route to Phobos

The Martian Moons Exploration (MMX) spacecraft is a JAXA mission to Mars and its moons Phobos and Deimos. MMX will be equipped with the Circum-Martian Dust Monitor (CMDM) which is a newly developed light-weight (mathrm {650,g}) large area (1,mathrm {m}^{2}) dust impact detector. Cometary meteoroid streams (also referred to as trails) exist along the orbits of comets, forming fine structures of the interplanetary dust cloud. The streams consist predominantly of the largest cometary particles (with sizes of approximately 100,mu mathrm { m} to 1 cm) which are ejected at low speeds and remain very close to the comet orbit for several revolutions around the Sun. The Interplanetary Meteoroid Environment for eXploration (IMEX) dust streams in space model is a new and recently published universal model for cometary meteoroid streams in the inner Solar System. We use IMEX to study the detection conditions of cometary dust stream particles with CMDM during the MMX mission in the time period 2024 to 2028. The model predicts traverses of 12 cometary meteoroid streams with fluxes of 100,mu mathrm { m} and bigger particles of at least 10^{-3},mathrm {m}^{-2},mathrm {day}^{-1} during a total time period of approximately 90 days. The highest flux of 0.15,mathrm {m}^{-2},mathrm {day}^{-1} is predicted for comet 114P/Wiseman-Skiff in October 2026. With its large detection area and high sensitivity CMDM will be able to detect cometary meteoroid streams en route to Phobos. Our simulation results for the Mars orbital phase of MMX also predict the occurrence of meteor showers in the Martian atmosphere which may be observable from the Martian surface with cameras on board landers or rovers. Finally, the IMEX model can be used to study the impact hazards imposed by meteoroid impacts onto large-area spacecraft structures that will be particularly necessary for crewed deep space missions.

Solar orbiter: mission to study the sun [Space innovation

Designing a spacecraft that can image the Sun as closely as possible without melting the delicate instruments has been a challenge. But scientists' luck could be about to change.LAUNCHED IN February 2020 from Cape Canaveral, a 1.7-tonne spacecraft called the Solar Orbiter aims to get up-close images of the Sun from 42 million kilometres away, while measuring its energetic behaviour in real-time. The suite of 10 on-board instruments will enable it to uniquely marry the study of events in the Sun's gaseous corona, measure its magnetic fields, and sample the solar wind as it flows past the spacecraft as a stream of energetic particles.

КОМПОНЕНТ ТЕМНОЇ МАТЕРІЇ І СОНЦЕ

Some consequences from the hypothesis of the origin of particles of one of the components of dark matter are presented. The reason for the hypothesis was the observational data of stellar radiation, considered through the prism of the relationship of all phenomena in Nature and the law of conservation of energy. It is argued that a part of the stellar electromagnetic radiation, which does not participate in the interaction with baryonic matter, will not wander forever in space. This radiation will interact with a subtle level of matter, continuously giving it its energy, shifting to the microwave region. In this frequency region, two quanta of close energies can form a neutral boson of spin 0, or spin 2, on opposite “courses”. Based on the observed spectrum of cosmic microwave radiation, it is assumed that these Bose particles have a continuous mass spectrum. These light nonrelativistic bosons are precisely the component of the thin medium that interacts with stellar radiation, taking energy from it. Bose particles participate in gravitational interactions. This means that in addition to the distribution of dark matter around galaxies, an increased concentration of particles in the form of large clouds can be observed in it. If an internal shock wave appears in such a cloud, located far from galactic streams of baryon particles, it will destroy the particles of the cloud, creating “strange radio circles” visible exclusively in the radio range. The gravitational interaction causes dark particles to drift towards large clusters of visible matter. The process of their drift to massive objects will be accompanied by resistance from the outgoing stellar radiation. Therefore, near the surface of a burning star, these particles themselves will resist the outgoing radiation, shifting it towards longer wavelengths. The plasma ejected by the star, with sufficient energy of its particles, is capable of destroying the particles of the dark component, creating pairs of photons and providing itself with "seed" quanta for bremsstrahlung. Free quanta remaining from the decay of dark particles will give microwave radiation. Therefore, burning stars should exhibit a redshift in the emission spectra and microwave radiation. Taking a certain model in the distribution of the dark component of matter near the Sun, it is possible to predict the nature of the redshift in the spectra of its radiation as the observation point moves along the solar disk from its center to the limb. A similar conclusion is made regarding the intensity of microwave radiation near the surface of the star. The galactic movement of the Sun should lead to some temperature effects associated with a denser counter flow of dark particles to the corresponding area of the solar surface. Knowing the direction of motion of the Sun in the Galaxy, based on the results of the temperature deviation on the surface of the star, one can determine the local speed and direction of movement of the cloud of the dark component of matter.

Packing fraction of clusters formed in free-falling granular streams based on flash x-ray radiography

We study the packing fraction of clusters in free-falling streams of spherical and irregularly shaped particles using flash x-ray radiography. The estimated packing fraction of clusters is low enough to correspond to coordination numbers less than 6. Such coordination numbers in numerical simulations correspond to aggregates that collide and grow without bouncing. Moreover, the streams of irregular particles evolved faster and formed clusters of larger sizes with lower packing fraction. This result on granular streams suggests that particle shape has a significant effect on the agglomeration process of granular materials.

Novel Fluidized Bed Particle Classifier for Application in Calcium Looping With Indirect Heat Transfer – Experiments and Simulations

This article summarizes a detailed scientific study of a particle classification system to be used in a fully integrated regenerative calcium looping (FICaL) system for CO2 capture. In conventional calcium looping, the required calcination heat is provided by a separate oxyfuel combustor, which needs an air separation unit (ASU) to provide the required oxygen for the process. The ASU demands a considerable amount of power, which gives an energy penalty of typically 5 % to the power plant. However, in the FICaL system, the required heat for the calcination is instead supplied indirectly from the main combustor in the power plant, so there is a no need for an ASU in the system. Based on process simulation studies done with Aspen Plus®, this may reduce the energy penalty to values in the order of 1-2 %. The indirect heat transfer is done by using inert heat transfer (HT) particles that are heated up in the combustor and then transferred to the calciner where the sorbent material is heated up after mixing with the hotter inert particles. Thereby the sorbent material is calcined. However, after calcination, the sorbent and heat transfer particles have to be separated. Hence, an efficient classifier is required. The current work has therefore focused on designing, constructing and doing experiments in a novel particle classification system. A novel cross-flow fluidized bed classifier was designed, using computational fluid dynamics (CFD) simulations as a tool, in order to separate the sorbent and HT particles exiting from the calciner. The classifier, which has no mechanical moving parts exposed to very high temperature, can be operated under the required high-temperature conditions prevailing in a full-scale plant. Two different cold-flow lab-scale versions of the classifier was built and used for a large number of experiments. In the classification, the aim is to minimize the loss of sorbent particles via the bottom exit from the classifier, and also to minimize the loss of HT particles via the top exit from the classifier. The second and improved version was able to classify very well a mixture of down-scaled sorbent particles (zirconia) and down-scaled HT particles (steel). The experiments with the improved classifier version gave particle losses in the order of 2-3 %, values that are close to what can be seen as acceptable in a full-scale hot-flow system. Extensive CFD simulations were carried out with the commercial software Barracuda® 17.1 to investigate in detail how the different particle types behave in the classifier. Even if the exact particle losses were not well predicted, Barracuda was able to predict the general gas-solids flow behavior and proved to be a useful tool in the design process. Different drag models were used to reproduce the experimental findings and validate the CFD model. Barracuda was also used to simulate the classification process under hot-flow conditions and indicated that the classifier will also perform well under such conditions. The results of the corresponding research work are promising as the classifier is able to give a high degree of purity of the particle streams leaving the classifier. The iterative design and modelling effort from this research work has produced a functional, high-efficiency classification concept.

Dehumidification Analysis of Rotary Solid Desiccant Wheel & Packed Bed System

Moisture transport is one of the major challenges in desiccant dehumidification. The transfer of moisture basically involves transfer of heat between moist air and desiccant particles as well as the mass transferal of moisture between moist air and desiccant particles. Type of desiccant dehumidification analysis is heating with dehumidification. Warmth move between sodden air and desiccants likewise gains consideration since temperature appropriation significantly influences the mass exchange execution through desiccant isotherms. The warmth and mass exchange between a clammy air stream and desiccant particles is dissected. Surface dissemination is noticed to overwhelm mass exchange within the silica gel particles. Here in this paper, we have compared the three diffusion coefficients Ordinary, Knudson and surface diffusion both for packed bed system and rotary desiccant system. Also, two models of move coefficients are introduced here and analyzed. Pseudo gas side controlled model usages an observational gas side mass exchange coefficient to represent dissemination opposition on strong side. Solid side resistance model settles the dissemination condition and is the finest exact as far as move coefficients. Notwithstanding, it makes examination considerably more clear.

Experimental study of a string-based counterflow wet electrostatic precipitator for collection of fine and ultrafine particles

ABSTRACT Wet electrostatic precipitators (WESP) have been widely studied for collecting fine and ultrafine particles, such as diesel particulate matter (DPM), which have deleterious effects on human health. Here, we report an experimental and numerical simulation study on a novel string-based two-stage WESP. Our new design incorporates grounded vertically aligned polymer strings, along which thin films of water flow down. The water beads, generated by intrinsic flow instability, travel down the strings and collect charged particles in the counterflowing gas stream. We performed experiments using two different geometric configurations of WESP: rectangular and cylindrical. We examined the effects of the WESP electrode bias voltage, air stream velocity, and water flow rate on the number-based fractional collection efficiency for particles of diameters ranging from 10 nm to 2.5 μm. The collection efficiency improves with increasing bias voltages or decreasing airflow rates. At liquid-to-gas (L/G) as low as approximately 0.0066, our design delivers a collection efficiency over 70% even for fine and ultrafine particles. The rectangular and cylindrical configurations exhibit similar collection efficiencies under nominally identical experimental conditions. We also compare the water-to-air mass flow rate ratio, air flow rate per unit collector volume, and collection efficiency of our string-based design with those of previously reported WESPs. The present work demonstrates a promising design for a highly efficient, compact, and scalable two-stage WESPs with minimal water consumption. Implications: Wet Electrostatic Precipitators (WESPs) are highly effective for collecting fine particles in exhaust air streams from various sources such as diesel engines, power plants, and oil refineries. However, their large-scale adoption has been limited by high water usage and reduced collection efficiencies for ultrafine particles. We perform experimental and numerical investigation to characterize the collection efficiency and water flow rate-dependence of a new design of WESP. The string-based counterflow WESP reported in this study offers number-based collection efficiencies >70% at air flow rates per collector volume as high as 4.36 (m3/s)/m3 for particles of diameters ranging from 10 nm – 2.5 μm, while significantly reducing water usage. Our work provides a basis for the design of more compact and water-efficient WESPs.

Concentration profiles of ions and particles under hydrodynamic focusing in Y-shaped square microchannel

Three-dimensional ion and particle concentrations under hydrodynamic focusing in a Y-shaped square microchannel are numerically simulated to clarify the decrease of the ion concentration along the flow direction within the focused particle stream. The simulation model is theoretically governed by the laminar flow and advection–diffusion equations. The governing equations are solved by the finite volume method. The ion and particle concentration distributions at five cross sections after the confluence of the branch channels are analyzed in 30 cases in which the sheath to sample flow rate ratio Qsh/Qsam and the Reynolds number Re are varied as parameters. The results show that the decrease of the cross-sectional average ion concentration along the flow direction within the particle stream overline{c}_{i} is described by the diffusion length during the residence time with a characteristic velocity scale. In addition, the deformation of the particle stream due to inertial effects is described by a scaled Reynolds number that is a function of the flow rate ratio. The simulated particle stream thicknesses are validated by theory and a simple experiment. This paper reveals the relationship between the ion and particle concentrations and the dimensionless parameters for hydrodynamic focusing in the Y-shaped square microchannel under typical conditions.

Application of the catalytic probe method for measuring the concentration of oxygen atoms in Ar/O2 plasma of a low-pressure arc

The monitoring of the degree of oxygen dissociation in the discharge plasma is critical for various plasma applications associated with the etching and oxidation of surfaces or the reactive deposition of oxide coatings. The use of existing measurement techniques is limited owing to their complexity, significant error rate, or application conditions. This study deals with the development of a catalytic probe method for measuring the degree of oxygen dissociation in dense arc discharge plasma. A method for measuring and processing the experimental results is presented, which allows the determination of the thermal contribution of the heterogeneous recombination of oxygen atoms at a high total heating power of the catalytic probe by particle streams and plasma radiation. The atomic oxygen concentration was measured in low-pressure arc plasma with a self-heating hollow cathode in an Ar/O2 mixture with changes in the discharge current and oxygen partial pressure over a wide range of 30–70 A and 0.2–0.6 Pa, respectively. It has been demonstrated that the maximum degree of oxygen dissociation (up to 25% of the O2 content) is achieved at the maximum discharge current and is practically independent of the oxygen flow, whereas the highest concentration of atomic oxygen is achieved when the maximum current and O2 flow values are combined. This conclusion is important for technologies based on plasma-chemical processes in high-current discharges.

Experimental investigation of fiber orientation effect on mechanical and erosive wear performance of TiO2 filled woven jute fiber based epoxy composites

Depleting finite resources and environmental conditions caused by derived synthetic fiber based polymer composites urged researchers to develop a substitute eco-friendly and bio degradable polymer composites in an economical manner by replacing synthetic fiber with natural fibers derived from plant,animals and industrial by products, having inherent properties like biodegradability, availability, renewability, low density, better specific mechanical properties, lower weight to strength ratio, unique acoustic characteristics however some demerits like hydrophobic in nature, poor bonding between fiber and matrix and the corresponding high moisture absorption. Out of all natural fibers, jute has been extensively considered for many engineering applications due to its availability. Most of the composites are exposed to dusty environment which leads to solid particle erosion, an investigation of their erosion attributes are of fundamental significance. Erosion wear test conducted by blasting a stream of solid particles against the target causes wear on surface. For a composite, its mechanical behaviour and many factors that influence the solid particle erosion. Attempts have been made to find the mechanical properties and erosion wear behavior of jute fiber reinforced composites at different orientation of fiber in addition of TiO 2 . The composites samples with different fiber orientation of woven jute fiber at 2 wt% of filler material were fabricated. Enhancement of tensile and flexural properties of jute fiber/epoxy composite with TiO 2 filler at 90° orientation of fiber erosive wear resistance improved on addition of TiO 2 filler material but the orientation of fiber doesn’t showed any considerable significance on erosive wear rate.

АКТУАЛЬНІ ЗАВДАННЯ ШЛІХОВОГО АНАЛІЗУ СУЧАСНИХ ДОННИХ ОСАДКІВ

Gold and other heavy minerals often form scaly, leafy, needle-like or split crystals, dendrites of complex shape, individuals and aggregates with a large number of internal cavities. Significant mobility of these particles in water and air streams causes their separation from the psammitic component of sediment and deposition together with clay minerals. During preparatory stages for mineralogical analysis, such crystals of heavy minerals fall into slime part. According to classical algorithm of schlich mineralogical analysis slime part is thrown away. So it leads to losses of rich minerals and an incorrect analysis. The main purpose of the article is to present the new algorithm for the preparation of the bottom sediments samples for the mineralogical analysis and to demonstrate practical benefits of it. Authors propose the meliorated methods of mineralogical analysis considering comprehensive study of test material. The real natural composition of ore minerals in the sediments consists of adding the data "heavy concentrate-1" and "heavy concentrate-2". This provides an increase in industrial value of minerals by 10-30%, compared with the methods of prospecting that operate today. Such detailed analysis showed that modern bottom sediments include both natural components and man-made materials (plastic, polyethylene, synthetic fibers and fabrics, fuel, various types of petroleum products, metallurgical and household waste). Mineralogical analysis can be used as an ecological method for assessing the environmental pollution and reviewing the types of pollutants. The estimation of mineral reserves according to new methodology opens opportunities for profitable field development of poor polymetallic deposits. The study of bottom sediments by such a method indicates the need to clean hydrogeoecosystems and stimulates the development of new recycling methods in the economy and the waste-free production, for example, cleaning beaches from heavy metals and waste, complex sludge processing after dredging works in riverbeds, berths and port waters.

PHANTOM MODEL OF DISTRIBUTION OF VIRAL OBJECTS IN A PANDEMIC. PART 2

Introduction. Preliminary consideration of the problem of the spread of viruses in space, studied by the authors [1], proves that the nature of their movement depends on the shape of these objects, and therefore the main aspects of the geometric dimensions of object’s presence area in interaction with other objects projects, including at the field level. Since the research was conducted under the assumption of formalizing the ideal structure of presence zone of (distribution) of material particles, the relevance of further research by the requirements for the need to determine the actual size of the flows is confirmed.Research results. The main purpose of this study was to continue to create a model for the spread of viruses as material particles in the surrounding space. As a result of analytical modeling of the nature of the spread of the body of the virus in the environment, it is shown that the virus as a physical object is under the constant action of various forces on the way from source to consumer. At the last stage, it is inhibited in the near-surface layer, although it is hardly possible to call it a full-fledged inhibition, because at a constant pulse the free path length is reduced. In the near-surface layer, the flow of the medium has a turbulent flow around the surface. Based on the study, it was determined that the geometric shape, or rather its phantom, play a major role in its movement in the environment. Thus, simulation of particle motion in space has shown that, as a physical object, a virus cannot form a rigid impact situation because it has a fairly large pandanus zone of receptors. The pandanus zone of the virus has a number of rarefied receptors that significantly soften the impact.Conclusions. Thus, the peculiarities of the spread of the flow of viruses in the environment under the presence of certain conditions of interaction of objects are considered. The analytical model of the propagation of fluxes of viral objects as streams of material particles in space-time coordinates is substantiated and the main features of such motion in the near-surface environments of the object and at a distance from it are determined.In further research, the phantom model of the propagation of streams of viral objects in space requires modeling of motion and touching the surface of the object at the level of different types of touching, depending on the state of their interaction.

Investigation on ignition behaviors of pulverized coal particles in a tubular swirl burner

This paper intensively investigated the ignition of turbulent coal flames in a novel fully-mixed tubular swirl burner. The Nikon D300s digital camera was used to capture the statistical ignition behavior of dispersed coal particle streams in different ambiences. Meanwhile, the combustion dynamics of individual coal particles were also recorded by means of high-speed photography. Two low-rank coal samples, Hulunbel lignite and Zhundong coal, were tested in this study. The ignition delay times of coal particles in the swirl burner were compared with those in a flat-flame burner. In contrast to previous work on a laminar flat-flame burner, the current experimental results show that the turbulent ambience significantly enhances the ignition of all coal samples, which is exceptionally pronounced under high temperature and low oxygen conditions. In addition, the sensitivity analysis suggests that both the enhanced heat and mass transfer contribute to the early ignition in turbulence. The effect of elevated mass transfer coefficient turns prominent in low oxygen fraction ambience, wherein the volatile barrier effect is suppressed by the enhanced mixing process. The combined effect of turbulence favors the shifting of ignition modes to the heterogeneous-dominant region. Last but not least, the ceased volatile flame that visualized in turbulent low oxygen ambience further confirms the important role of heterogeneous ignition.

Bi-directional streaming of particles accelerated at the STEREO-A shock on 2008 March 9

ABSTRACT We present an interpretation of anisotropy and intensity of supra-thermal ions near a fast quasi-perpendicular reverse shock measured by Solar Terrestrial Relations Observatory Ahead (ST-A) on 2008 March 9. The measured intensity profiles of the supra-thermal particles exhibit an enhancement, or ‘spike’, at the time of the shock arrival and pitch-angle anisotropies before the shock arrival are bi-modal, jointly suggesting trapping of near-scatter-free ions along magnetic field lines that intersect the shock at two locations. We run test-particle simulations with pre-existing upstream magnetostatic fluctuations advected across the shock. The measured bi-modal upstream anisotropy, the nearly field-aligned anisotropies up to ∼15 min upstream of the shock, as well as the ‘pancake-like’ anisotropies up to ∼10 min downstream of the shock are well reproduced by the simulations. These results, in agreement with earlier works, suggest a dominant role of the large-scale structure (100s of supra-thermal proton gyroradii) of the magnetic field in forging the early-on particle acceleration at shocks.