Quasistatic heat front and delocalized heat flux

Luciani, J. F.; Mora, P.; Pellat, R.

doi:10.1063/1.865052

Cited by 138 publications

(61 citation statements)

References 15 publications

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“…The same applies, of course, to the new kernels. Consequently, the formula g~ ~^t Mm X 2 (dx'nT^2^LH0) (6) 4ir(3m e ) lu J dx exactly recovers results from Eq. (5) for both smooth (or classical) and steep limit profiles, and could be used for intermediate profiles, as a very convenient approximation.…”

Section: Sgkdd/ S%ldd-soldd /Ss'jdd and K(0)/l(q) -I(0)/j(0)mentioning

confidence: 52%

“…They also gave evidence supporting the use of a two-term Legendre-polynomial expansion withyo^/ M , for arbitrary Z, . 6 It would thus be possible to extend the formalism here continued from Ref. 1, which is strictly valid for Z, large (A ee >/l w ), to values Z, ~ 1.…”

Section: Sgkdd/ S%ldd-soldd /Ss'jdd and K(0)/l(q) -I(0)/j(0)mentioning

confidence: 99%

“…Physical arguments, and a fit to numerical simulations and the classical limit, 5,6 led them to an equation like (6) with a kernel 3lV61nA ee y written here in present variables and for Z, large; the ratio In A ei An A ee stems for their using a single Coulomb logarithm. They also gave an integrodifferential iterative procedure to determine/(its Legendre expansion broken at some order) and then q T ; 6 from the first iteration and setting £" = 0, they derived (6) with a kernel, given graphically, quite close to L. Referring to E = 0 as the isobaric case, they took n T = const: note that this would imply R T = 0.…”

Section: Sgkdd/ S%ldd-soldd /Ss'jdd and K(0)/l(q) -I(0)/j(0)mentioning

confidence: 99%

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Nonlocal electron heat flux revisited

Sanmartin

Ramírez

Feria

1990

Physics of Fluids B: Plasma Physics

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A known nonlocal model of electron heat flux, applying for (scale length/thermal ion-electron mean-free path) of order Z) /2 (e*/T) 312 , ionization number Z, large, and e*~ 6.5 T (the energy of electrons carrying most of the flux), is reconsidered. The large e*/T ratio simplifies the complete formalism. A simple flux formula, exact for both smooth and steep profiles, is given. Thermoelectric effects and other models are discussed.Heat transport is essential to the physics of laser targets. Albritton et al. x gave a self-consistent calculation of nonlocal heat flux q in a weakly collisional regime. In the present work we reconsider their model and give new results and simplifications.We first review the model conditions not quite stated in Ref. 4 In A el , the symbols being as usual. In the free-streaming operator, and based on both the small value of the mass ratio and flow quasineutrality, (i) we have neglected the time derivative d / dt and terms arising in the ion frame from ion hydrodynamics. The energy dependence of mean-free paths allows us to assume that (ii) main-body electron are near-Maxwellian, but (iii) those contributing dominantly to q, characterized by an energy e* ~ 6.5 T, 3 are not. Taking Z, large allows us to also assume (iv) that e* electrons are nonetheless nearisotropic. For e~e* and /=:/> (isotropic), 2 C« = 7n?k " x (

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Section: Sgkdd/ S%ldd-soldd /Ss'jdd and K(0)/l(q) -I(0)/j(0)mentioning

confidence: 52%

Section: Sgkdd/ S%ldd-soldd /Ss'jdd and K(0)/l(q) -I(0)/j(0)mentioning

confidence: 99%

Section: Sgkdd/ S%ldd-soldd /Ss'jdd and K(0)/l(q) -I(0)/j(0)mentioning

confidence: 99%

See 1 more Smart Citation

Nonlocal electron heat flux revisited

Sanmartin

Ramírez

Feria

1990

Physics of Fluids B: Plasma Physics

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“…Recent progress has been made, however [38,39], which may allow the inclusion of nonlocal conduction effects into radiation hydrodynamic codes in the future.…”

Section: B Flare Heating Radiative Losses and Thermal Conductionmentioning

confidence: 99%

Radiation Hydrodynamics in Solar Flares

Fisher

1986

International Astronomical Union Colloquium

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Solar flares are currently understood as the explosive release of energy stored in the form of stressed magnetic fields. In many cases, the released energy seems to take the form of large numbers of electrons accelerated to high energies (the nonthermal electron "thick target" model), or alternatively plasma heated to very high temperatures behind a rapidly moving conduction front (the "thermal" model). The transport of this energy into the remaining portion of the atmosphere results in violent mass motion and strong emission across the electromagnetic spectrum. Radiation processes play a crucial role in determining the ensuing plasma motion.One important phenomenon observed during flares is the appearance in coronal magnetic loops of large amounts of upflowing, soft X-ray emitting plasma at temperatures of 1 − 2 × 10 7 [K]. It is believed that this is due to chromospheric evaporation, the process of heating cool (T ∼ 10 4 [K]) chromospheric material beyond its ability to radiate. Detailed calculations of thick target heating show that if nonthermal electrons heat the chromosphere directly, then the evaporation process can result in explosive upward motion of X-ray emitting plasma if the heating rate exceeds a threshold value. In such a case, upflow velocities approach an upper limit of roughly 2.35c s as the heating rate is increased beyond the threshold, where c s is the sound speed in the evaporated plasma. This is known as explosive evaporation. If the flare heating rate is less than the threshold, evaporation takes place indirectly through thermal conduction of heat deposited in the corona by the energetic electrons. Upflows in this case are roughly 10 to 20% of the upper limit. Evaporation by thermal model heating always takes place through thermal conduction, and the computed upflow speeds seem to be about 10% to 20% of the upper limit, independent of the energy flux.The pressure increase in the evaporated plasma for either the thick target or thermal model leads to a number of interesting phenomena in the flare chromosphere. The sudden pressure increase initiates a downward moving "chromospheric condensation", an overdense region which gradually decelerates as it -2 -accretes material and propagates into the gravitationally stratified chromosphere. Solutions to an equation of motion for this condensation shows that its motion decays after about one minute of propagation into the chromosphere. When the front of this downflowing region is supersonic relative to the atmosphere ahead of it, a radiating shock will form. If the downflow is rapid enough, the shock strength should be sufficient to excite UV radiation normally associated with the transition region, and furthermore, the radiating shock will be brighter than the transition region. These results lead to a number of observationally testable relationships between the optical and ultraviolet spectra from the condensation and radiating shock.

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“…Because of the increasing mean free path with particle kinetic energy, the situation can already change for mean free path on the order of or longer than 1% of the length scale of plasma gradients [1]. This gives rise to kinetic effects such as streaming plasmas and non-local transport, which are intensely studied because of their importance in many plasma environments, such as high-density laser-produced plasmas [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and astrophysical plasmas like the solar wind [19], solar atmosphere [20,21], solar flares [22], and supernovae [23].…”

Section: Introductionmentioning

confidence: 99%

Emergence of kinetic behavior in streaming ultracold neutral plasmas

et al. 2015

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We create streaming ultracold neutral plasmas by tailoring the photoionizing laser beam that creates the plasma. By varying the electron temperature, we control the relative velocity of the streaming populations, and, in conjunction with variation of the plasma density, this controls the ion collisionality of the colliding streams. Laser-induced fluorescence is used to map the spatially resolved density and velocity distribution function for the ions. We identify the lack of local thermal equilibrium and distinct populations of interpenetrating, counter-streaming ions as signatures of kinetic behavior. Experimental data is compared with results from a one-dimensional, two-fluid numerical simulation.

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Quasistatic heat front and delocalized heat flux

Cited by 138 publications

References 15 publications

Nonlocal electron heat flux revisited

Nonlocal electron heat flux revisited

Radiation Hydrodynamics in Solar Flares

Emergence of kinetic behavior in streaming ultracold neutral plasmas

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