Plasma Vortex Research Articles

On the mechanism of the formation of magnetohydrodynamic vortices in the solar plasma

Based on the magnetohydrodynamic (MHD) equations for an incompressible conductive viscous fluid, the possible mechanism of the formation of giant MHD vortices recently discovered in the solar atmosphere (chromosphere) is analyzed. It is assumed that these vortices arise in the regions of the solar surface (photosphere) with ascending flows of hot plasma that arrives from the inner regions of the Sun as a result of thermal convection and is accelerated upward under the action of the chromospheric plasma pressure gradient. It is shown that, under the assumption of plasma incompressibility and flow continuity, the ascending plasma flows induce converging radial plasma flows, which create the convective and Coriolis nonlinear hydrodynamic forces due to the nonzero initial vorticity of the chromospheric plasma caused by Sun’s rotation. The combined action of these two forces leads to the exponential acceleration of the solid-body rotation of plasma inside the ascending flow, thereby creating a vortex that generates an axial magnetic field, in agreement with astrophysical observations.

On the origin of dust vortices in complex plasmas under microgravity conditions

Under microgravity conditions, microparticles in a radio-frequency plasma form an extended dust cloud. In such clouds, self-excited large-scale vortices are observed. New experimental observations are reported, which exhibit a simple double vortex structure or a more complex quadrupole-like topology. Modeling the fields of the main acting forces, namely, the electric field force and the ion drag force, and calculating the curl of these forces reveal their non-conservative character and the possible driving mechanism of the vortices. It is shown that the curl of the ion drag force and of the electric field force has opposite sign and the combination could thus lead to the complex structures, also found in the observations.

Kinetic study of ion-acoustic plasma vortices

The kinetic theory of electron plasma waves with finite orbital angular momentum has recently been introduced by Mendonca. This model shows possibility of new kind of plasma waves and instabilities. We have extended the theory to ion-acoustic plasma vortices carrying orbital angular momentum. The dispersion equation is derived under paraxial approximation which exhibits a kind of linear vortices and their Landau damping. The numerical solutions are obtained and compared with analytical results which are in good agreement. The physical interpretation of the ion-acoustic plasma vortices and their Landau resonance conditions are given for typical case of Maxwellian plasmas.

Photo-catalytic titanium oxide film deposition by atmospheric TPCVD using vortex Ar plasma jet

In order to generate the vortex plasma jet, the vortex flow creation nozzle (vortex nozzle) was equipped at the head of the plasma torch. Consequently, by equipment of the vortex nozzle, plasma jet released from the plasma torch ran along the inner wall of the vortex nozzle and the plasma jet was changed into vortex plasma jet in the vortex nozzle. As for the titanium oxide film deposition, anatase rich titanium oxide film with uniform thickness distribution could be obtained on the 304 stainless steel substrate. The film deposition rate at the center on the condition of 30 mm in deposition distance was approximately 8 μm/min. Besides, since the anatase rich film indicated hydrophilic and methylene-blue droplet on the film was decolored by UV irradiation in cases of methylene-blue wettability and decoloration tests, it was proved that the anatase rich film have photocatalytic properties. Especially, in case of the film deposited on the condition of 30 mm in deposition distance, methylene-blue droplet was perfectly decolored by 48 h UV irradiation. From these results, this technique was found to have high potential for uniform film deposition by TPCVD.

On the nature and location of the proposed twin vortex systems in Saturn's polar upper atmosphere

AbstractTwin vortices in Saturn's northern and southern polar ionospheres have been proposed as the drivers of the ∼10.7 h periodicities in the magnetosphere. We critically analyze this model from an atmospheric perspective, identifying two broad problems: first, the difficulty in reconciling a ∼10.7 h periodicity with the strongly subcorotational flows that are observed in the polar ionosphere; second, the very large energy requirement for sustaining the vortices against Joule dissipation. We propose a model in which the twin vortex originates neither in the plasma nor in the thermosphere but deeper in the atmosphere, around 750 km altitude. At this altitude the gas is expected to be close to corotation, and Joule dissipation is low. A twin vortex system at this altitude blowing laterally across the Hall conductance gradient at the main auroral oval generates field‐aligned currents which are qualitatively similar to those driven by a plasma vortex or thermospheric vortex at higher altitudes.

Solar wind pressure pulse‐driven magnetospheric vortices and their global consequences

AbstractWe report the in situ observation of a plasma vortex induced by a solar wind dynamic pressure enhancement in the nightside plasma sheet using multipoint measurements from Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites. The vortex has a scale of 5–10 Re and propagates several Re downtail, expanding while propagating. The features of the vortex are consistent with the prediction of the Sibeck (1990) model, and the vortex can penetrate deep (~8 Re) in the dawn‐dusk direction and couple to field line oscillations. Global magnetohydrodynamics simulations are carried out, and it is found that the simulation and observations are consistent with each other. Data from THEMIS ground magnetometer stations indicate a poleward propagating vortex in the ionosphere, with a rotational sense consistent with the existence of the vortex observed in the magnetotail.

Flow Separation Control Using Plasma Vortex Generator

This paper represents a series of experiment to figure out plasma vortex generator as a means of separation flow control. Typical conventional vortex generator is a vane normal to wall and has a yaw angle against a main flow. This yaw angle gives a penalty of drag increase at the sacrifice of the separation suppression. A plasma vortex generator developed here has a yaw angle of 0° and thus the penalty could be minimized. An exposed electrode was installed on the Kapton vane tip, and another electrode was embedded in the vane. Stream-wise counter-rotating vortices are produced by the vane type plasma vortex generator at downstream that helps to control flow separation. The effect of the plasma vortex generator has been investigated on a turbulent boundary layer on a 20°-inclined slope. The separation flow was visualized by using a smoke wire, and the velocity profiles were measured using a hot-wire anemometer. The plasma vortex generators suppressed the separation similarly as the conventional vortex generator, and its performance was validated.

The evolution of flux pileup regions in the plasma sheet: Cluster observations

Bursty bulk flows (BBFs) play an important role for the mass, energy, and magnetic flux transport in the plasma sheet, and the flow pattern in and around a BBF has important consequences for the localized energy conversion between the electromagnetic and plasma mechanical energy forms. The plasma flow signature in and around BBFs is often rather complicated. Return flows and plasma vortices are expected to exist at the flanks of the main flow channel, especially near the inner plasma sheet boundary, but also farther down‐tail. A dipolarization front (DF) is often observed at the leading edge of a BBF, and a flux pileup region (FPR) behind the DF. Here we present Cluster data of three FPRs associated with vortex flows observed in the midtail plasma sheet on 15 August 2001. According to the principles of Fu et al. (2011, 2012c), two of the FPRs are considered to be in an early stage of evolution (growing FPRs). The third FPR is in a later stage of evolution (decaying FPR). For the first time, the detailed energy conversion properties during various stages of the FPR evolution have been measured. We show that the later stage FPR has a more complex vortex pattern than the two earlier stage FPRs. The two early stage FPR correspond to generators, E·J<0, while the later stage FPR only shows weak generator characteristics and is instead dominated by load signatures at the DF, E·J>0. Moreover, to our knowledge, this is one of the first times BBF‐related plasma vortices have been observed to propagate over the spacecraft in the midtail plasma sheet at geocentric distances of about 18RE. Our observations are compared to recent simulation results and previous observations.

On the formation of streamwise vortices by plasma vortex generators

AbstractThe streamwise vortices generated by dielectric-barrier-discharge plasma actuators in the laminar boundary layer were investigated using particle image velocimetry to understand the vortex-formation mechanisms. The plasma vortex generator was oriented along the primary flow direction to produce a body force in the spanwise direction. This created a spanwise-directed wall jet which interacted with the oncoming boundary layer to form a coherent streamwise vortex. It was found that the streamwise vortices were formed by the twisting and folding of the spanwise vorticity in the oncoming boundary layer into the outer shear layer of the spanwise wall jet, which added its own vorticity to increase the circulation along the actuator length. This is similar to the delta-shaped, vane-type vortex generator, except that the circulation was enhanced by the addition of the vorticity in the plasma jet. It was also observed that the plasma vortex was formed close to the wall with an enhanced wall-ward entrainment, which created strong downwash above the actuator.

Comparison between vortices created and evolving during fixed and dynamic solar wind conditions

Abstract. We employ Magnetohydrodynamic (MHD) simulations to examine the creation and evolution of plasma vortices within the Earth's magnetosphere for steady solar wind plasma conditions. Very few vortices form during intervals of such solar wind conditions. Those that do remain in fixed positions for long periods (often hours) and exhibit rotation axes that point primarily in the x or y direction, parallel (or antiparallel) to the local magnetospheric magnetic field direction. Occasionally, the orientation of the axes rotates from the x direction to another direction. We compare our results with simulations previously done for unsteady solar wind conditions. By contrast, these vortices that form during intervals of varying solar wind conditions exhibit durations ranging from seconds (in the case of those with axes in the x or y direction) to minutes (in the case of those with axes in the z direction) and convect antisunward. The local-time dependent sense of rotation seen in these previously reported vortices suggests an interpretation in terms of the Kelvin–Helmholtz instability. For steady conditions, the biggest vortices developed on the dayside (about 6 RE in diameter), had their rotation axes aligned with the y direction and had the longest periods of duration. We attribute these vortices to the flows set up by reconnection on the high-latitude magnetopause during intervals of northward Interplanetary Magnetic Field (IMF) orientation. This is the first time that vortices due to high-latitude reconnection have been visualized. The model also successfully predicts the principal characteristics of previously reported plasma vortices within the magnetosphere, namely their dimension, flow velocities, and durations.

Fragmentation of electric currents in the solar corona by plasma flows

We consider a magnetic configuration consisting of an arcade structure and a detached plasmoid, resulting from a magnetic reconnection process, as is typically found in connection with solar flares. We study spontaneous current fragmentation caused by shear and vortex plasma flows. An exact analytical transformation method was applied to calculate self-consistent solutions of the nonlinear stationary MHD equations. The assumption of incompressible field-aligned flows implies that both the Alfven Mach number and the mass density are constant on field lines. We first calculated nonlinear MHS equilibria with the help of the Liouville method, emulating the scenario of a solar eruptive flare configuration with plasmoids and flare arcade. Then a Mach number profile was constructed that describes the upflow along the open magnetic field lines and implements a vortex flow inside the plasmoid. This Mach number profile was used to map the MHS equilibrium to the stationary one. We find that current fragmentation takes place at different locations within our configuration. Steep gradients of the Alfven Mach number are required, implying the strong influence of shear flows on current amplification and filamentation of the MHS current sheets. Crescent- or ring-like structures appear along the outer separatrix, butterfly structures between the upper and lower plasmoids, and strong current peaks close the lower boundary. Impressing an intrinsic small-scale structure on the upper plasmoid results in strong fragmentation of the plasmoid. Hence fragmentation of current sheets and plasmoids is an inherent property of MHD theory. Transformations from MHS into MHD steady-states deliver fine-structures needed for plasma heating and acceleration of particles and bulk plasma flows in dissipative events that are typically connected to magnetic reconnection processes in flares and coronal mass ejections.

Interaction between plasma structures in an unstable ionospheric plasma

A vortex structure renders additional stability to plasma irregularities stretched along magnetic field lines. Plasma irregularities extended over several tens of kilometers are registered with rocket and satellite equipment in the topside ionosphere. The registered scale of irregularities depends on the spatial and time resolution of the equipment used. Irregular structures were registered in the ionosphere during experiments with barium clouds and jets, when a plasma irregularity separated into strata extended over several meters and several kilometers across the geomagnetic field. It has been indicated that plasma vortices can be generated in an unstable plasma in a situation when its quasi-neutrality is disturbed. Local geomagnetic field disturbances will be caused by the appearance of a proper vortex magnetic field. Plasma vortices can interact in an inhomogeneous plasma with an unstable electron component. Such interactions are related to the transformation of the phase volume of free electrostatic oscillations in the frequency-wave vector space.

Mathematical modeling of energy release in a plasma vortex reactor

Mathematical modeling of energy release in a plasma vortex reactor

Electron temperature gradient excited vortices in plasmas with impurities

Vortices formed from electron temperature gradient instabilities in impurity-containing plasmas have been investigated. It is shown that the impurities in the plasma can have a significant effect on the characteristics of the vortex, in particular its amplitude and thus its effectiveness in particle and energy transport across the confining magnetic field.

On TIE‐GCM simulation of the evening equatorial plasma vortex

It has already been shown that the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIE‐GCM) is capable of reproducing the pre‐reversal enhancement (PRE) of the equatorial zonal electric field. However, the ability of TIE‐GCM to reproduce the post‐sunset plasma vortex, an important feature of the evening equatorial ionosphere closely related to the PRE, has been overlooked and had yet to be addressed. In order to address the ability of TIE‐GCM to reproduce the vortex, we examined model simulations of the plasma flow pattern in the geomagnetic equatorial plane and compared the simulations with ground‐based radar observations. We found that TIE‐GCM is indeed capable of reproducing the overall features of the post‐sunset equatorial plasma vortex pattern. We also found that both E and F region dynamos in TIE‐GCM dictate the main features of the vertical shear in the zonal plasma drifts that is part of the evening vortex. The contribution of vertical currents to the shear, however, is not negligible. Comparison of simulation results with radar measurements of the vortex indicates that the model can still be improved to better match the observations.

S056022 プラズマボルテックスジェネレーターによるはく離制御

S056022 プラズマボルテックスジェネレーターによるはく離制御

A massively parallel, multi-disciplinary Barnes–Hut tree code for extreme-scale N-body simulations

The efficient parallelization of fast multipole-based algorithms for the N-body problem is one of the most challenging topics in high performance scientific computing. The emergence of non-local, irregular communication patterns generated by these algorithms can easily create an insurmountable bottleneck on supercomputers with hundreds of thousands of cores. To overcome this obstacle we have developed an innovative parallelization strategy for Barnes–Hut tree codes on present and upcoming HPC multicore architectures. This scheme, based on a combined MPI–Pthreads approach, permits an efficient overlap of computation and data exchange. We highlight the capabilities of this method on the full IBM Blue Gene/P system JUGENE at Jülich Supercomputing Centre and demonstrate scaling across 294,912 cores with up to 2,048,000,000 particles. Applying our implementation pepc to laser–plasma interaction and vortex particle methods close to the continuum limit, we demonstrate its potential for ground-breaking advances in large-scale particle simulations.

Publisher's Note: On the possibility of fast vortices in the cuprates: A vortex plasma model analysis of THz conductivity and diamagnetism in La2−xSrxCuO4[Phys. Rev. B84, 100511(R) (2011)

Publisher's Note: On the possibility of fast vortices in the cuprates: A vortex plasma model analysis of THz conductivity and diamagnetism in La<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>2</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:math>Sr<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mi>x</mml:mi></mml:msub></mml:math>CuO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>4</mml:mn></mml:msub></mml:math>[Phys. Rev. B<b>84</b>, 100511(R) (2011)

Publisher’s Note: On the possibility of fast vortices in the cuprates: A vortex plasma model analysis of THz conductivity and diamagnetism in La2−xSrxCuO4[Phys. Rev. B84, 100511(R) (2011)

Received 29 September 2011DOI:https://doi.org/10.1103/PhysRevB.84.139901©2011 American Physical Society

Kelvin-Helmholtz instability at Saturn's magnetopause: Hybrid simulations

[1] Recent observations of a plasma vortex in Saturn's dayside outer magnetosphere is evidence that the Kelvin-Helmholtz instability (KHI) is operating at Saturn's morning magnetospheric boundaries. Kelvin-Helmholtz vortices can mediate the transport of mass, momentum, energy and magnetic flux at the magnetospheric boundaries, making KHI an important mechanism through which the solar wind interacts with the magnetosphere. We derive plasma properties from the Cassini Plasma Spectrometer (CAPS) during the December 13, 2004 magnetopause boundary encounter. These plasma properties (ion temperature, density, composition, and plasma flow) are used as input parameters for a two-dimensional hybrid simulation of the KHI unstable planetward edge of Saturn's boundary layer region. We investigate the effect of heavy magnetospheric ions on the KHI evolution and test the growth rates as a function of magnetosonic Mach number. We compare our simulation results with the plasma data, estimate diffusion coefficients due to KHI plasma mixing (D > 1010 m2 s−1) and energy transported into Saturn's magnetosphere (∼40 GW) due to the KHI unstable boundaries and conclude that mass transfer processes at Saturn's magnetopause boundary can play a significant role in driving magnetospheric dynamics.