scholarly journals Nonlocal electron transport in laser created plasmas

1994 ◽  
Vol 12 (3) ◽  
pp. 387-400 ◽  
Author(s):  
P. Mora ◽  
J.F. Luciani
Keyword(s):  
Heat Flux ◽  
Heat Flow ◽  
Temperature Gradient ◽  
Collision Operator ◽  
Mean Free Path ◽  
Electron Collision ◽  
Large Temperature ◽  
Laser Plasma Interaction ◽  
Electron Heat ◽  
Steep Temperature Gradient

The classical linear Spitzer-Härm formula has been shown to lead to an overestimation of the electron heat flux in laser-plasma interaction experiments. We briefly review the classical theory of heat transport in a plasma, and give a simplified demonstration of the Spitzer-Härm formula. The electron heat conductivity is calculated for a large value of the ion charge Z. Correction due to a finite value of Z is evaluated with a simplified electron-electron collision operator. We then show that in a steep temperature gradient, the collisional mean free path of the electrons that transport the energy may be larger than the scale length of the temperature gradient. In this case the Spitzer-Härm formula overestimates the actual heat flux in the main part of the temperature gradient, and predicts a too small heat flux slightly away from the location of the large temperature gradient.A nonlocal macroscopic formula, which is a sort of convolution of the Spitzer-Härm heat flux by a delocalization function, is shown to accurately describe the electron heat flow in both smooth and steep temperature gradients. This nonlocal formula for the heat flow is analytically justified. A selection of slightly different delocalization functions proposed in the literature is compared to the original one and to the results of Fokker-Planck calculations of the heat flow.

Light scattering by phonons in the presence of a heat flow

1968 ◽  
Vol 46 (24) ◽  
pp. 2843-2845 ◽  
Author(s):  
Allan Griffin
Keyword(s):  
Light Scattering ◽  
Heat Flow ◽  
Temperature Gradient ◽  
Free Path ◽  
Mean Free Path ◽  
Photon Scattering ◽  
The Mean ◽  
Anti Stokes

If the temperature in an insulating crystal decreases in the z-direction, there are more phonons with momentum qz > 0 than with qz < 0. The resulting difference between the Stokes and anti-Stokes Brillouin intensities is proportional to the mean free path of the phonon involved and to the temperature gradient. The effect should be observable by either neutron or photon scattering.

scholarly journals The Thermal Conductivity of Carbon Nanotubes with Defects and Intramolecular Junctions

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Qiaoli Zhou ◽  
Fanyan Meng ◽  
Zhuhong Liu ◽  
Sanqiang Shi
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Temperature Gradient ◽  
Temperature Profile ◽  
Free Path ◽  
Mean Free Path ◽  
Nonequilibrium Molecular Dynamics ◽  
Large Temperature ◽  
Large Temperature Gradient

The thermal conductivity of various carbon nanotubes with defects or intramolecular junctions was studied using nonequilibrium molecular dynamics approach. The results show that the thermal conductivity of both armchair and zigzag carbon nanotubes increased with the decrease of the radius of the tube. The thermal conductivity of armchair tube is higher than that of zigzag tube when the radii of the two tubes are kept almost same. Discontinuities appear on the temperature profile along the tube axial at the region of IMJ, resulting in the large temperature gradient and thus lower thermal conductivity of(n,n)/(m,0)tube with one IMJ and(m,0)/(n,n)/(m,0)tube with two IMJs. For the(m,0)/(n,n)/(m,0)tube with two IMJs, phonon mean free path of the middle(n,n)tube is much smaller than that of the isolate(n,n)tube.

scholarly journals Observations and modelling of first-year ice growth and simultaneous second-year ice ablation in the Prydz Bay, East Antarctica

2017 ◽  
Vol 58 (75pt1) ◽  
pp. 59-67 ◽  
Author(s):  
Jiechen Zhao ◽  
Bin Cheng ◽  
Qinghua Yang ◽  
Timo Vihma ◽  
Lin Zhang
Keyword(s):  
Heat Flux ◽  
Temperature Gradient ◽  
East Antarctica ◽  
Prydz Bay ◽  
Large Temperature ◽  
First Year ◽  
Conductive Heat ◽  
Oceanic Heat Flux ◽  
Conductive Heat Flux ◽  
Second Year

ABSTRACT The seasonal cycle of fast ice thickness in Prydz Bay, East Antarctica, was observed between March and December 2012. In March, we observed a 0.16 m thickness gain of 0.22 m-thick first-year ice (FYI), while 1.16 m-thick second-year ice (SYI) nearby simultaneously ablated by 0.59 m. A 1-D thermodynamic sea-ice model was applied to identify the factors that led to the simultaneous growth of FYI and melt of SYI. The different evolutions were explained by the difference in the conductive heat flux between the FYI and SYI. As the FYI was thin, there was a large temperature gradient between the ice base and the colder ice surface. This generated an upward conductive heat flux, which was larger than the heat flux from the ocean to the ice base, yielding basal growth of ice. In the case of the thicker SYI the temperature gradient and, hence, the conductive heat flux were smaller, and not sufficient to balance the oceanic heat flux at the ice base, yielding basal ablation. Penetration of solar radiation affected the conductive heat flux in both cases, and the model results were sensitive to the initial ice temperature profile and the uncertainty of the oceanic heat flux.

Solution of a Heat Flow Problem

1951 ◽  
Vol 4 (1) ◽  
pp. 12 ◽  
Author(s):  
JRM Radok
Keyword(s):  
Heat Flux ◽  
Heat Flow ◽  
Temperature Gradient ◽  
Heat Source ◽  
Boundary Conditions ◽  
Flow Problem ◽  
Zero Temperature ◽  
Insulating Materials ◽  
Constant Temperature Gradient ◽  
Flow Through

This paper deals with the heat flow through a rectangle subject to the following boundary conditions : One end is completely insulated (without heat flux across it) and at the opposite end a constant temperature gradient is maintained; the remaining sides radiate into a medium which is at zero temperature. Initially the rectangle is at zero temperature. The problem is converted into a homogeneous one by considering a rectangle of twice the length with a uniformly distributed heat source along the centre line. The solution of this problem is effected by using particular solutions given in Carslaw and Jaeger. The problem considered is of interest in connection with the testing of heat-insulating materials.

Electron heat transport in a steep temperature gradient

1989 ◽  
Vol 1 (4) ◽  
pp. 741-749 ◽  
Author(s):  
J. H. Rogers ◽  
J. S. De Groot ◽  
Z. Abou‐Assaleh ◽  
J. P. Matte ◽  
T. W. Johnston ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Heat Transport ◽  
Electron Heat ◽  
Steep Temperature Gradient

The role of electron heat flux in guide-field magnetic reconnection

2004 ◽  
Vol 11 (12) ◽  
pp. 5387-5397 ◽  
Author(s):  
Michael Hesse ◽  
Masha Kuznetsova ◽  
Joachim Birn
Keyword(s):  
Heat Flux ◽  
Magnetic Reconnection ◽  
Guide Field ◽  
Electron Heat

Boundary-value problems in the kinetic theory of gases. Part 2. Thermal creep

1971 ◽  
Vol 45 (4) ◽  
pp. 759-768 ◽  
Author(s):  
M. M. R. Williams
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Temperature Gradient ◽  
Kinetic Theory ◽  
Effective Thermal Conductivity ◽  
Half Space ◽  
Thermal Creep ◽  
Kinetic Theory Of Gases ◽  
Boundary Wall ◽  
Creep Velocity

The effect of a temperature gradient in a gas inclined at an angle to a boundary wall has been investigated. For an infinite half-space of gas it is found that, in addition to the conventional temperature slip problem, the component of the temperature gradient parallel to the wall induces a net mass flow known as thermal creep. We show that the temperature slip and thermal creep effects can be decoupled and treated quite separately.Expressions are obtained for the creep velocity and heat flux, both far from and at the boundary; it is noted that thermal creep tends to reduce the effective thermal conductivity of the medium.

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