Viscous Plasma Research Articles

Anisotropic viscous dissipation in three-dimensional magnetic merging solutions

Aims. We consider viscous and resistive energy dissipation in the flaring solar corona. Methods. We compute energy dissipation rates, associated with magnetic merging in three dimensions. We examine an exact 3D solution for steady magnetic merging in a viscous resistive incompressible plasma. We use the Braginskii stress tensor to model viscous effects and derive scalings for the resistive and viscous dissipation rates. We evaluate the dissipation rates for typical parameters of solar active regions. Results. Large-scale advective flows required to sustain resistive current sheets are shown to be associated with significant viscous losses. For plausible dimensionless resistivities (inverse Lundquist numbers), whether classical η ≤ 10 −14 or anomalous η ≤ 10 −8 , viscous loss rates greatly exceed the resistive loss rates of the current layer and can approach flare-like rates of 10 28 erg s −1 .

Numerical study of magnetohydrodynamic viscous plasma flow in rotating porous media with Hall currents and inclined magnetic field influence

A numerical solution is developed for the viscous, incompressible, magnetohydrodynamic flow in a rotating channel comprising two infinite parallel plates and containing a Darcian porous medium, the plates lying in the x–z plane, under constant pressure gradient. The system is subjected to a strong, inclined magnetic field orientated to the positive direction of the y-axis (rotational axis, normal to the x–z plane). The Navier–Stokes flow equations for a general rotating hydromagnetic flow are reduced to a pair of linear, viscous partial differential equations neglecting convective acceleration terms, for primary velocity (u′) and secondary velocity (v′) where these velocities are directed along the x and y axes. Only viscous terms are retained in the momenta equations. The model is non-dimensionalized and shown to be controlled by a number of dimensionless parameters. The resulting dimensionless ordinary differential equations are solved using a robust numerical method, Network Simulation Methodology. Full details of the numerics are provided. The present solutions are also benchmarked against the analytical solutions presented recently by Ghosh and Pop [Ghosh SK, Pop I. An analytical approach to MHD plasma behaviour of a rotating environment in the presence of an inclined magnetic field as compared to excitation frequency. Int J Appl Mech Eng 2006;11(4):845–856] for the case of a purely fluid medium (infinite permeability). We study graphically the influence of Hartmann number (Ha, magnetic field parameter), Ekman number (Ek, rotation parameter), Hall current parameter (Nh), Darcy number (Da, permeability parameter), pressure gradient (Np) and also magnetic field inclination (θ) on primary and secondary velocity fields. Additionally we investigate the effects of these multiphysical parameters on the dimensionless shear stresses at the plates. Both primary and secondary velocity are seen to be increased with a rise in Darcy number, owing to a simultaneous reduction in Darcian drag force. Primary velocity is seen to decrease with an increase in Hall current parameter (Nh) but there is a decrease in secondary velocity. The study finds important applications in magnetic materials processing, hydromagnetic plasma energy generators, magneto-geophysics and planetary astrophysics.

Microcirculatory effects of intravenous fluids in critical illness: plasma expansion beyond crystalloids and colloids

Plasma expanders are reviewed to determine their ability to restore microvascular function as a means for extending the transfusion trigger and delaying the use of blood transfusions. This outcome is currently achievable because of the emergence of a new understanding of optimal tissue function that prioritizes maintenance of functional capillary density, which results from the normalization of blood viscosity via the increase in plasma viscosity with new viscogenic colloids. Use of viscous plasma expanders in experimental models of extreme hemodilution, hemorrhagic shock and endotoxemia shows that the limiting factor in anemia is not oxygen-carrying capacity but the decline of microvascular function due to the lowering of functional capillary density. In support of this hypothesis, we find that viscogenic colloids including high-molecular-weight starches, dextrans, polyvinylpyrrolidone, keratin and polyethylene glycol-conjugated albumin maintain or restore microvascular function in extreme hemodilution, polyethylene glycol-conjugated albumin yielding the best results. Preclinical studies show that polyethylene glycol-conjugated albumin at concentrations in the range of 2-4% extends the transfusion trigger, providing the more extended and complete microvascular and systemic recovery from hemorrhagic shock, extreme hemodilution and endotoxemia, postponing the need of reestablish intrinsic blood oxygen-carrying capacity to hemoglobin concentrations lower than those associated with accepted transfusion triggers.

Axisymmetric magnetorotational instability in ideal and viscous laboratory plasmas

The original analysis of the axisymmetric magnetorotational instability (MRI) by Velikhov (Sov. Phys. JETP 9, 995 (1959)) and Chandrasekhar (Proc. Nat. Acad. Sci. 46, 253 (1960)), applied to the ideally conducting magnetized medium in the laboratory conditions and restricted to the incompressible approximation, is extended by allowing for the compressibility. Thereby, two additional driving mechanisms of MRI are revealed in addition to the standard drive due to the negative medium rotation frequency gradient (the Velikhov effect). One is due to the squared medium pressure gradient and another is a combined effect of the pressure and density gradients. For laboratory applications, the expression for the MRI boundary with all the above driving mechanisms and the stabilizing magnetoacoustic effect is derived. The effects of parallel and perpendicular viscosities on the MRI in the laboratory plasma are investigated. It is shown that, for strong viscosity, there is a family of MRI driven for the same condition as the ideal one. It is also revealed that the presence of strong viscosity leads to additional family of instabilities called the viscosity-driven MRI. Then the parallel-viscositydriven MRI looks as an overstability (oscillatory instability) possessing both the growth rate and the real part of oscillation frequency, while the perpendicular-viscosity MRI is the aperiodical instability.

Stability analysis of viscous Z-pinch plasma with a sheared axial flow

Within the magnetohydrodynamics (MHD) frame, we analyse the effect of viscosity on magneto-Rayleigh–Taylor (MRT) instability in a Z-pinch configuration by using an exact method and an approximate method separately. It is demonstrated that the plasma viscosity indeed has a stabilization effect on the MRT mode in the whole wavenumber region, and its influence increases with the perturbation wavenumber increasing. After the characteristics and feasibility of the approximate method have been investigated, we apply it to the stability analysis of viscous plasma where a sheared axial flow (SAF) is involved, and we attain an analytical dispersion relation. It is suggested that the viscosity and the SAF are complemental with each other, and a wide wavenumber range of perturbation is possible to be restrained if the SAF and the viscosity are large enough. Finally, we calculate the possible value of viscosity parameter according to the current experimental conditions, and the results show that since the value of viscosity is much less than the threshold value, its mitigation effect is small enough to be neglected. The role of the viscosity in the stabilization becomes considerable only if special techniques are so developed that the Z-pinch plasma viscosity can be increased greatly.

Damping of slow magnetoacoustic waves in an inhomogeneous coronal plasma

We study the propagation and dissipation of slow magnetoacoustic waves in an inhomogeneous viscous coronal loop plasma permeated by uniform magnetic field. Only viscosity and thermal conductivity are taken into account as dissipative processes in the coronal loop. The damping length of slow-mode waves exhibit varying behaviour depending upon the physical parameters of the loop in an active region AR8270 observed by TRACE. The wave energy flux associated with slow magnetoacoustic waves turns out to be of the order of 106 erg cm−2 s−1 which is high enough to replace the energy lost through optically thin coronal emission and the thermal conduction below to the transition region. It is also found that only those slow-mode waves which have periods more than 240s provide the required heating rate to balance the energy losses in the solar corona. Our calculated wave periods for slow-mode waves nearly match with the oscillation periods of loop observed by TRACE.

Nonaxisymmetric magnetorotational instability in ideal and viscous plasmas

The excitation of magnetorotational instability (MRI) in rotating laboratory plasmas is investigated. In contrast to astrophysical plasmas, in which gravitation plays an important role, in laboratory plasmas it can be neglected and the plasma rotation is equilibrated by the pressure gradient. The analysis is restricted to the simple model of a magnetic confinement configuration with cylindrical symmetry, in which nonaxisymmetric perturbations are investigated using the local approximation. Starting from the simplest case of an ideal plasma, the corresponding dispersion relations are derived for more complicated models including the physical effects of parallel and perpendicular viscosities. The Friemann–Rotenberg approach used for ideal plasmas is generalized for the viscous model and an analytical expression for the instability boundary is obtained. It is shown that, in addition to the standard effect of radial derivative of the rotation frequency (the Velikhov effect), which can be destabilizing or stabilizing depending on the sign of this derivative in the ideal plasma, there is a destabilizing effect proportional to the fourth power of the rotation frequency, or, what is the same, to the square of the plasma pressure gradient, and to the square of the azimuthal mode number of the perturbations. It is shown that the instability boundary also depends on the product of the plasma pressure and density gradients, which has a destabilizing effect when it is negative. In the case of parallel viscosity, the MRI looks like an ideal instability independent of viscosity, while, in the case of strong perpendicular viscosity, it is a dissipative instability with the growth rate inversely proportional to the characteristic viscous decay rate. We point out, however, that the modes of the continuous range of the magnetohydrodynamics spectrum are not taken into account in this paper, and they can be more dangerous than those that are considered.

Flavors in an expanding plasma

We consider the effect of an expanding plasma on probe matter by determining time-dependent D7 embeddings in the holographic dual of an expanding viscous plasma. We calculate the chiral condensate and meson spectra including contributions of viscosity. The chiral condensate essentially confirms the expectation from the static black hole. For the meson spectra we propose a scheme that is in agreement with the adiabatic approximation. New contributions arise for the vector mesons at the order of the viscosity terms.

Comparison of a novel viscous platelet additive solution and plasma: preparation and in vitro storage parameters of buffy‐coat‐derived platelet concentrates

We developed a viscous platelet additive solution (PAS) based on MacoPharma's SSP+ but containing hydroxyethyl starch to address the poor osmotic balance and low yield associated with conventional PAS for the storage of buffy-coat platelet concentrates (PC). Pools of four buffy-coats were made into leucoreduced PCs (n = 5) suspended either in plasma or viscous PAS. After determination of platelet recoveries, the PCs were stored under standard conditions. On days 1, 2, 3, 5, 7 and 9, PCs were tested for mean platelet volume, platelet concentration, soluble protein concentration, CD62 expression, platelet morphology, partial pressure of oxygen and partial pressure of carbon dioxide, glucose and lactate concentration, pH, extent of shape change, and hypotonic shock response (HSR). Platelets were prepared with greater ease using the viscous PAS and had improved platelet yield. PCs stored in either plasma or viscous PAS displayed similar storage characteristics to day 9. On days 7 and 9 of storage, platelets stored in viscous PAS displayed significantly lower (P < 0.05) CD62 expression and higher HSR scores than those stored in plasma. Alteration of the viscosity of PAS improves platelet recovery during processing and may prolong platelet quality at the later stages of storage.

Saddle-node bifurcation and modulational instability associated with the pulse propagation of dust ion-acoustic waves in a viscous dusty plasma: A complex nonlinear Schrödinger equation

Using the standard reductive perturbation technique, a nonlinear Schrödinger equation (NLSE) with complex coefficients is derived in a dusty plasma consisting of positive ions, nonthermal electrons, and charged dust grains. The effect of ion kinematic viscosity is taken into consideration, which makes the coefficients of NLSE complex. By means of a matching approach, the appearance mechanism of static pulses through a saddle-node bifurcation in the complex nonlinear Schrödinger equation is studied analytically. The analytical results are in good agreement with the direct numerical simulation. The modulational instability analysis is carried out for the dust ion-acoustic envelope solitary waves. The important role of the real part of the complex group velocity in the propagation of the one-dimensional wave packets in homogeneous active medium is predicted.

Effect of sheared equilibrium plasma rotation on the classical tearing mode in a cylindrical geometry

The effect of sheared equilibrium plasma rotation on the stability of tearing modes in an Ohmic (low plasma β) regime is investigated. It is found, by means of numerical MHD simulations in a cylindrical geometry, that plasma rotation in the equivalent toroidal direction can result either in the increase or in the decrease of the instability growth rate. Perpendicular plasma viscosity and plasma rotation shear at the modes’ rational surface play a key role on assessing the effect of shear flow. While destabilizing for low viscosity plasmas (ratio of the resistive to viscous diffusion time scales τR∕τV≪1), for viscous plasmas (τR∕τV&amp;gt;1) shear flow reduces the growth rate. Above a given threshold in the rotation shear (that depends on the ratio τR∕τV) a tearing mode, unstable in the absence of rotation, can be stabilized. The effect of sheared toroidal flow on mode stability, in both viscosity regimes that are considered in the paper, is qualitatively independent of the aspect ratio.

Comparison of 7-Day Storage of Buffy-Coat Derived Platelet Concentrates in an Osmotically Balanced, Interface Stabilizing Platelet Storage Solution and in Plasma.

The use of platelet additive solutions (PAS) for the storage of buffy-coat derived platelet concentrates (PC) could conserve plasma resources and reduce post-transfusion reactions. However, PASs are difficult to handle in a production environment where their relative low viscosity produces an unstable interface between the platelet rich plasma and the red cell pellet. In the current study, a comparison is drawn between buffy-coat derived PCs (4 buffy-coats per pool) stored over 7 days either in plasma or in a novel Viscous PAS that contains 26 % plasma as a by-product of the buffy-coat pooling process. The increased viscosity (1.18 cp at 37°C) of the PAS results in a stable interface during processing. Similar, though more consistent platelet recoveries from buffy-coat pools (BCP) are achieved by the Viscous PAS (77.0 ± 2.6%) as compared to plasma (73.7 ± 5.9 %). These are significantly higher (p<0.05) than recoveries using conventional PASs (64.5 ± 2.1 %). On day 7, platelet concentration, mean platelet volume (MPV), and soluble protein concentration in PCs stored using Viscous PAS (782 ± 87 x 109 cells/L, 9.1 ± 0.5fL, 15.0 ± 1.6 mg/L, respectively) and plasma (840 ± 104 x 109 cells/L, 9.0 ± 0.7fL, 56.09 ± 9.2 mg/L, respectively) were not significantly different from their corresponding day 1 parameters (837 ± 84 x 109 cells/L, 9.1 ± 0.3 fL, 13.5 ± 0.2 mg/L) respectively for Viscous PAS and (830 ± 73 x 109 cells/L, 8.3 ± 0.5 fL, 56.6 ± 6.5 mg/mL) and for plasma. This indicates that Viscous PAS and plasma maintain platelet integrity to a similar degree during 7-day storage. Both storage media maintain pH around 7.20 until day 7. However, the rate of glucose consumption and lactate production of PCs stored in Viscous PAS (0.3365 mmol/L.day, and 0.7591 mmol/L.day) was roughly half that of the rate exhibited by PCs stored in plasma (0.8447 mmol/L.day, and 1.4258 mmol/L.day). As lactate production and glucose consumption are correlated with in vivo platelet recovery (Goodrich et al., 2006) this augurs well for platelets stored in Viscous PAS. Monitoring the extent of shape change (ESC) and morphology scores for PCs in either of the storage media showed no significant difference on day 7. However, CD62 surface expression and the hypotonic shock response (HSR) were significantly better at day 7 (p<0.05) for platelets stored in the Viscous PAS (37.43 ± 3.31% and 75.76 ± 10.95%, respectively) than stored in plasma (58.37 ± 11.71% and 49.79 ± 15.34%, respectively). We have developed a PAS that is easy to handle in a production environment and because of its osmotic balance and realtive viscosity exhibits equivalent or better storage parameters over a 7 day period than does plasma.

Shear-driven magnetic reconnection in viscous resistive incompressible plasmas

Planar magnetic reconnection, driven by shear flows in viscous resistive incompressible plasmas, is analyzed. Time-dependent profiles of the flow velocity and the reconnecting magnetic field are computed by solving the magnetohydrodynamic equations for disturbances of a magnetostatic configuration. The resulting asymptotic profiles for large times are characterized by boundary layers, formed at the boundaries of the region, rather than by a localized reconnecting current sheet within the region. Analysis of steady viscoresistive solutions confirms that a smooth solution, reached by a dynamically evolving system, must be nonlocalized. The results imply that at least two-dimensional shear flows are required for driving magnetic reconnection in viscous resistive plasmas.

On the Propagation and Dissipation of Alfvén Waves in Coronal Holes

We underline the importance of Alfven wave dissipation in the magnetic funnels through the viscous and resistive plasma. Our results show that Alfven waves are one of the primary energy sources in the innermost part of coronal holes where the solar wind outflow starts.

Viscous Damping of Non-Adiabatic MHD Waves in an Unbounded Solar Coronal Plasma

The damping of MHD waves in solar coronal magnetic field is studied taking into account thermal conduction and compressive viscosity as dissipative mechanisms. We consider viscous homogeneous unbounded solar coronal plasma permeated by a uniform magnetic field. A general fifth-order dispersion relation for MHD waves has been derived and solved numerically for different solar coronal regimes. The dispersion relation results three wave modes: slow, fast, and thermal modes. Damping time and damping per periods for slow- and fast-mode waves determined from dispersion relation show that the slow-mode waves are heavily damped in comparison with fast-mode waves in prominences, prominence–corona transition regions (PCTR), and corona. In PCTRs and coronal active regions, wave instabilities appear for considered heating mechanisms. For same heating mechanisms in different prominences the behavior of damping time and damping per period changes significantly from small to large wavenumbers. In all PCTRs and corona, damping time always decreases linearly with increase in wavenumber indicate sharp damping of slow- and fast-mode waves.

Slow magnetohydrodynamic waves in stratified and viscous plasmas

The propagation of slow magnetohydrodynamic waves in vertical thin flux tubes embedded in a vertically stratified plasma in the presence of viscosity is shown here to be governed by the Klein-Gordon-Burgers (KGB) equation, which is solved in two limiting cases assuming an isothermal medium in hydrostatic equilibrium surrounded by a quiescent environment. The results presented here can be applied to, e.g., study the propagation of slow magnetohydrodynamic waves generated by the granular buffeting motion in thin magnetic photospheric tubes. When the variation in the reduced velocity occurs over typical lengths much larger than the gravitational scale height, the KGB equation can be reduced to a Klein-Gordon equation describing the propagation of an impulse followed by a wake oscillating with the frequency reduced by viscosity and the solution has no spatial or temporal decay. However, in the other limiting case, i.e., typical variations in the reduced velocity occur over characteristic lengths much smaller than the gravitational scale height, waves have a temporal and spatial decay.

A Single-Tube Nucleic Acid Extraction, Amplification, and Detection Method Using Aluminum Oxide

A disposable 0.2-ml polymerase chain reaction (PCR) tube modified with an aluminum oxide membrane (AOM) has been developed for the extraction, amplification, and detection of nucleic acids. To assess the dynamic range of AOM tubes for real-time PCR, quantified herpes simplex virus (HSV) DNA was used to compare AOM tubes to standard PCR tubes. AOM PCR tubes used for amplification and detection of quantified HSV-1 displayed a crossing threshold (C(T)) shift 0.1 cycles greater than PCR tube controls. Experiments with HSV-1-positive cerebrospinal fluid (CSF) examined the extraction, amplification, and detection properties of the AOM tubes compared to the Qiagen DNA blood mini kit. The AOM extraction, amplification, and detection of HSV-1 in CSF displayed differences of less than one C(T) when compared to Qiagen-extracted samples. Experiments testing the AOM method using clinical CSF samples displayed 100% concordance with reported results. AOM tubes have no adverse effects on amplification or fluorescence acquisition by real-time PCR and can be effectively used for the extraction, amplification, and detection of HSV from CSF. The AOM single tube method is a fast, reliable, and reproducible technique for the extraction, amplification, and detection of HSV in CSF.

Resistive and viscous dynamics of finite-amplitude shear waves at a magnetic X-point

The dynamics and dissipation of axial shear waves, superposed on a planar magnetic X-point in a resistive viscous incompressible plasma, are analyzed numerically and analytically. The interplay of viscous and resistive effects is demonstrated by deriving solutions for various values of the scalar coefficients of viscosity and resistivity. These solutions show that viscous-resistive coupling can dramatically affect the global energy dissipation. When either viscosity or resistivity vanishes, the solutions are characterized by oscillatory decaying eigenmodes that maintain equipartition between the magnetic and kinetic energies. This behavior persists when resistivity is the dominant dissipation mechanism. When viscosity is the dominant dissipation mechanism, initial oscillations are followed by exponential decay at sufficiently long times. The applicability of the results to flares in solar active regions, where the viscous Reynolds number can be much smaller than the resistive one, is discussed.

Conserved functions and extended Grad–Shafranov equation for low vorticity viscous plasmas with nonlinear flows

Tokamak equilibrium has been analyzed with the magnetohydrodynamics nonlinear momentum equation in the low vorticity case. A large simplification in the analysis is obtained in this case compared with previous general treatments for rotating plasmas in tokamaks. Now pressure is not conserved around magnetic surfaces, however, other generalized functions have been found, which are conserved on each magnetic surface. A generalized Grad–Shafranov-type equation has been also derived for this case. How to determine the gradient of these new conserved functions on each magnetic surface from their value at one point of the corresponding surface is also shown.

Observation of Heat-Induced Particle Resuspension and Transport in a Plasma Chemical Vapor Deposition Chamber

The influences of gas viscous force, thermal stress, and plasma electrostatic force on heat-induced particle resuspension and transport in a plasma chemical vapor deposition (CVD) chamber were studied experimentally. Using an in situ particle measurement system in a plasma CVD chamber based on a laser light scattering method, it was observed that silica particles with a diameter of 600 nm dispersed on a wafer were resuspended when the wafer was heated. At a wafer temperature of 573 K, when the pressure in the chamber was being changed, the removal ratio of particles from the wafer exhibited a weak dependence on pressure in the range from 13.3 Pa (0.1 Torr) to 1.33 kPa (10 Torr). A theoretical calculation based on thermophoresis that considers a temperature jump could explain the trend of the experimental results. Since the removal ratio of particles from the wafer is greater with larger difference in the linear coefficients of thermal expansion between the wafer and the particles, it is considered that the particles are separated from the wafer due to thermal stress and are scattered towards the upper electrode by the force of thermophoresis. It has also been revealed that, when plasma discharge is applied, the removal ratio of particles is reduced due to the electrostatic force of charged particles.