Two-temperature Effects Research Articles

Non-local thermal transport impact on compressive waves in two-temperature coronal loops

Context. Observations of slow magnetoacoustic waves in solar coronal loops suggest that in hot coronal plasma, heat conduction may be suppressed in comparison with the classical thermal transport model. Aims. We link this suppression with the effect of the non-local thermal transport that appears when the plasma temperature perturbation gradient becomes comparable to the electron mean-free-path. Moreover, we consider a finite time of thermalisation between electrons and ions so that separate electron and ion temperatures can occur in the loop. Methods. We numerically compared the influence of the local and non-local thermal transport models on standing slow waves in one- and two-temperature coronal loops. To quantify our comparison, we used the period and damping time of the waves as commonly observed parameters. Results. Our study reveals that non-local thermal transport can result in either shorter or longer slow-wave damping times in comparison with the local conduction model due to the suppression of the isothermal regime. The difference in damping times can reach 80%. For hot coronal loops, we find that the finite equilibration between electron and ion temperatures results in an up to 50% longer damping time compared to the one-temperature case. These results indicate that non-local transport will influence the dynamics of compressive waves across a broad range of coronal plasma parameters with Knudsen numbers (the ratio of mean-free-path to temperature scale length) larger than 1%. Conclusions. In the solar corona, the non-local thermal transport shows a significant influence on the dynamics of standing slow waves in a broad range of plasma parameters, while two-temperature effects come into play for hot and less dense loops.

Reflection of quasi plasma wave in photo-piezo semiconductor medium with distinct higher order fractional derivative two temperature models

This article investigates the reflection of thermo-photo-piezo-elastic plane waves from a homogeneous, orthotropic, and piezo semiconductor medium during the photo-thermal process. A novel higher-order fractional dual-phase lag hyperbolic two-temperature model is employed to tackle this study. The analytical solution to the problem in the xz plane reveals the existence of five interconnected waves. The derivation of formulas for reflection coefficients and their corresponding energy ratios is performed for an incident quasi-plasma wave. Numerical computations determine the energy ratios for different angles of incidence. These energy ratios are visually represented in graphs, demonstrating the influence of higher-order parameters, two-temperature effects, fractional order derivatives, and various heat conduction models.

Analytical Model of Disk Evaporation and State Transitions in Accreting Black Holes

State transitions in black hole X-ray binaries are likely caused by gas evaporation from a thin accretion disk into a hot corona. We present a height-integrated version of this process, which is suitable for analytical and numerical studies. With radius r scaled to Schwarzschild units and coronal mass accretion rate to Eddington units, the results of the model are independent of black hole mass. State transitions should thus be similar in X-ray binaries and an active galactic nucleus. The corona solution consists of two power-law segments separated at a break radius r b ∼ 103(α/0.3)−2, where α is the viscosity parameter. Gas evaporates from the disk to the corona for r > r b , and condenses back for r < r b . At r b , reaches its maximum, . If at r ≫ r b the thin disk accretes with , then the disk evaporates fully before reaching r b , giving the hard state. Otherwise, the disk survives at all radii, giving the thermal state. While the basic model considers only bremsstrahlung cooling and viscous heating, we also discuss a more realistic model that includes Compton cooling and direct coronal heating by energy transport from the disk. Solutions are again independent of black hole mass, and r b remains unchanged. This model predicts strong coronal winds for r > r b , and a T ∼ 5 × 108 K Compton-cooled corona for r < r b . Two-temperature effects are ignored, but may be important at small radii.

Mathematical Model for the Deformation in a Modified Green-Lindsay Thermoelastic Medium with Nonlocal and Two-Temperature Effects

Mathematical Model for the Deformation in a Modified Green-Lindsay Thermoelastic Medium with Nonlocal and Two-Temperature Effects

Two-temperature effects in Hall-MHD simulations of the HIT-SI experiment

A two-temperature Hall-magnetohydrodynamic (Hall-MHD) model, which evolves the electron and ion temperatures separately, is implemented in the PSI-Tet 3D MHD code and used to model plasma dynamics in the Helicity Injected Torus–Steady Inductive (HIT-SI) experiment. The two-temperature model is utilized for HIT-SI simulations in both the PSI-Tet and NIMROD codes at a number of different injector frequencies in the 14.5–68.5 kHz range. At all frequencies, the NIMROD two-temperature model results in increased toroidal current, lower chord-averaged density, higher average temperatures, outward radial shift of the current centroid, and axial symmetrization of the current centroid, relative to the single-temperature NIMROD simulations. The two-temperature PSI-Tet model illustrates similar trends, but at high frequency operation, it exhibits lower electron temperature, smaller toroidal current, and decreased axial symmetrization with respect to the single-temperature PSI-Tet model. With all models, average temperatures and toroidal currents increase with the injector frequency. Power balance and heat fluxes to the wall are calculated for the two-temperature PSI-Tet model and illustrate considerable viscous and compressive heating, particularly at high injector frequency. Parameter scans are also presented for artificial diffusivity, wall temperature, and density. Both artificial diffusivity and the density boundary condition significantly modify the plasma density profiles, leading to larger average temperatures, toroidal current, and relative density fluctuations at low densities. A low density simulation achieves sufficiently high current gain (G &amp;gt; 5) to generate significant volumes of closed flux lasting 1–2 injector periods.

A wide-range model for simulation of aluminum plasma produced by femtosecond laser pulses

We use a wide-range model of thermodynamic, transport and optical properties for simulation of laser-induced dynamics of aluminum plasma. The model describes the laser energy absorption, electron thermal conductivity and two-temperature effects of electron-ion collisions as well as hydrodynamic motion of matter. The model successfully describes experiments on self-reflectivity in wide range of intensities, and angular dependence of reflectivity coefficient for S- and P-polarized pulses. Thus, the model can be used for prediction of the main parameters of aluminum plasma such as temperature, density, velocity, mean charge of ions for optimization of planned experiments.

Effect of Two Temperatures on Reflection Coefficient in Micropolar Thermoelastic with and without Energy Dissipation Media

The reflection of plane waves at the free surface of thermally conducting micropolar elastic medium with two temperatures is studied. The theory of thermoelasticity with and without energy dissipation is used to investigate the problem. The expressions for amplitudes ratios of reflected waves at different angles of incident wave are obtained. Dissipation of energy and two-temperature effects on these amplitude ratios with angle of incidence are depicted graphically. Some special and particular cases are also deduced.

Two-Temperature Effects on Plane Waves in Generalized Thermo-Microstretch Elastic Solid

In this article, the effect of two temperatures on plane waves propagating through a generalized-thermo-microstretch elastic half-space solid has been investigated. The surface of the medium is subjected to a mode-I crack, and the $$z$$ axis is pointing vertically into the medium. Two fascinating theories of generalized thermo-elasticity presented by Green and Naghdi and named as without energy dissipation (GN-II) and with energy dissipation (GN-III) have been used. Governing equations for each particular case are also derived, and a solution is obtained. An analytical technique of normal mode analysis is used to obtain the exact expressions for the displacement components, force stresses, the temperature, and the couple stresses distribution. The variations of the considered variables against the vertical distance are illustrated graphically. Comparisons are made with the results between type II and III in generalized-thermo-microstretch and in a particular case (without microstretch constants). Numerical work is also performed for a suitable material with the aim of illustrating the results. It is found that the maximum amplitude is obtained for the maximum value of the two temperature parametric constant.

Atomistic Modeling of Warm Dense Matter in the Two‐Temperature State

AbstractWarm dense matter is the state between the heated condensed matter and plasma. The importance of the development of warm dense matter theoretical description is determined by the fact that such conditions may arise in the variety of different scientific and industrial applications. For instance, warm dense matter is formed: in the matter impacted by femto‐ and picoseconds laser pulses; in nuclear materials at the formation of radiation track, etc. In these phenomena, the initial state of the system is a two‐temperature state and the electron temperature may be several orders higher than the ion one. In this work, the attempt of development of the united atomistic model of a warm dense matter is carried out. The special consideration is given to the twotemperature effects and the influence of the electron pressure on the behavior of ions. (© 2013 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Two-temperature accretion flows in magnetic cataclysmic variables: structures of post-shock emission regions and X-ray spectroscopy

We use a two-temperature hydrodynamical formulation to determine the temperature and density structures of the post-shock accretion flows in magnetic cataclysmic variables (mCVs) and calculate the corresponding X-ray spectra. The effects of two-temperature flows are significant for systems with a massive white dwarf and a strong white-dwarf magnetic field. Our calculations show that two-temperature flows predict harder keV spectra than one-temperature flows for the same white-dwarf mass and magnetic field. This result is insensitive to whether the electrons and ions have equal temperature at the shock, but depends on the electron–ion exchange rate, relative to the rate of radiative loss along the flow. White-dwarf masses obtained by fitting the X-ray spectra of mCVs using hydrodynamic models including the two-temperature effects will be lower than those obtained using single-temperature models. The bias is more severe for systems with a massive white dwarf.