Heat flux saturation in hydrodynamic soft X-ray solar flare plasmas

Craig, I. J. D.; Davys, J. W.

doi:10.1007/bf00173962

Cited by 6 publications

(3 citation statements)

References 11 publications

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“…To the extent that α c is an order-unity correction factor (that depends weakly on v e ), this applies also to the heat flux carried in the non-Maxwellian tail of the electron distribution. For a high-density laboratory plasma, though, Mannheimer & Klein (1975) showed that v c scales directly with v e (see also Smith & Lilliequist 1979;Craig & Davys 1984).…”

Section: Heat Conductionmentioning

confidence: 99%

Self‐consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence

Cranmer

Ballegooijen

Edgar

2007

ASTROPHYS J SUPPL S

594

804

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We present a series of models for the plasma properties along open magnetic flux tubes rooted in solar coronal holes, streamers, and active regions. These models represent the first self-consistent solutions that combine:(1) chromospheric heating driven by an empirically guided acoustic wave spectrum, (2) coronal heating from Alfvén waves that have been partially reflected, then damped by anisotropic turbulent cascade, and (3) solar wind acceleration from gradients of gas pressure, acoustic wave pressure, and Alfvén wave pressure. The only input parameters are the photospheric lower boundary conditions for the waves and the radial dependence of the background magnetic field along the flux tube. We have not included multifluid or collisionless effects (e.g., preferential ion heating) which are not yet fully understood. For a single choice for the photospheric wave properties, our models produce a realistic range of slow and fast solar wind conditions by varying only the coronal magnetic field. Specifically, a two-dimensional model of coronal holes and streamers at solar minimum reproduces the latitudinal bifurcation of slow and fast streams seen by Ulysses. The radial gradient of the Alfvén speed affects where the waves are reflected and damped, and thus whether energy is deposited below or above the Parker critical point. As predicted by earlier studies, a larger coronal "expansion factor" gives rise to a slower and denser wind, higher temperature at the coronal base, less intense Alfvén waves at 1 AU, and correlative trends for commonly measured ratios of ion charge states and FIP-sensitive abundances that are in general agreement with observations. These models offer supporting evidence for the idea that coronal heating and solar wind acceleration (in open magnetic flux tubes) can occur as a result of wave dissipation and turbulent cascade. Subject headings: MHD -solar wind -Sun: atmospheric motions -Sun: corona -turbulence -waves 1 Other models can be included if some of the above conditions are relaxed. For example, Hu et al. (2000) and Li (2002Li ( , 2003 considered wave-driven coronal heating with a lower boundary within the transition region (i.e., temperatures ranging between 6 × 10 4 and 8 × 10 5 K). See § 2 below for a comparison of the relevant physical assumptions and numerical approaches.

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Section: Heat Conductionmentioning

confidence: 99%

Self‐consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence

Cranmer

Ballegooijen

Edgar

2007

ASTROPHYS J SUPPL S

594

804

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“…Zhao et al (2019) conducted forward-modeling analysis based on their 2.5-dimensional magnetohydrodynamics (MHD) simulation, where the formation and eruption of an FR driven by photospheric converging motion in a chromosphere-transition-corona setup is simulated. The setup includes the effects of radiative cooling, anisotropic thermal conduction along the magnetic field lines, gravitational stratification, resistivity, viscosity and the thermal flux saturation effect (Craig & Davys 1984). Zhao et al (2019) concentrated on the large scale evolution and how it appears in various synthetic observational views.…”

Section: Introductionmentioning

confidence: 99%

Mesoscale Phenomena during a Macroscopic Solar Eruption

Zhao

Keppens

2020

ApJ

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Our previous magnetohydrodynamic (MHD) simulation of a macroscopic solar eruption discussed in Zhao et al. (2019) showed that the current sheet (CS) evolution during eruption went through four stages: the CS growth stage, the dynamic growth stage, the hot CS stage, and the dynamic hot CS stage. We now focus on various mesoscale phenomena associated with the ongoing reconnection. In the dynamic growth stage, the remnant chromospheric matter in the CS is quasi-periodically pushed into the prominence, inducing fast shocks propagating at a speed of 210 km • s −1 . In the hot CS phase, various shock features relevant for particle acceleration are identified throughout the flare loop. Finally, during both dynamic stages, we quantify the properties of magnetic islands. A typical island is accelerated to Alfvénic speed by the Lorentz force and cools down by radiative cooling and thermal conduction. It also tends to expand in size before colliding with another island, with the FR or with the flare arcade. Islands in the dynamic growth stage have a higher density and lower temperature, and vice versa in the dynamic hot CS stage. Islands tend to move upward in the dynamic growth stage, while almost equal fractions of downward-moving and upward-moving islands in the dynamic hot CS stage. Translating the island trajectories to phase space, we find that the functionẏ = (ay 2 + by + c) exp(λy) fits the trajectory well, and its two fixed points represent the creation and the annihilation of the island.

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“…Cowie和McKee [60] 得到饱和的热传导能流公式为F sat =sign(b•∇T)5φρc s 3 b, 其中φ=0.3, ρ是质量密度, c s 是等温声速, sign(x)取x的正负符号. Craig和Davys [61] 通过耀斑环的数值模拟, 发现耀斑过程中热传导能流会出现饱和, 物质流动成为能量输运的主角. 当电子密度很低, 温度标高小于电子碰撞自由程时, 如在10个太阳半径之外的太阳风里, 需要考虑无碰撞的热传导能流αn e kTv [62] , 其中常数 α≈1, n e 是电子数密度, k是Boltzman常数, v是流体运动速度.…”

Section: 经典热传导能流是在扩散假设下计算的当电子unclassified

Radiative magnetohydrodynamics simulations on solar corona

Xia¹

2018

Sci. Sin.-Phys. Mech. Astron.

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The outmost layer of solar atmosphere, corona, has many activities, such as flares, coronal mass ejections, solar prominences, and coronal rains. In order to fully understand the nonlinear physical process of these activities, one of the most popular approaches is to construct multidimensional numerical models via radiative magnetohydrodynamic numerical simulations. To simulate macroscopic coronal physics, we need to numerically solve magnetohydrodynamic equations coupled with radiative cooling, thermal conduction, and heating. The mainstream numerical methods to numerically solve these problems are introduced. The numerical scheme to solve the magnetohydrodynamic equations is composed of reconstruction to cell-interface values, approximate Riemann solver, methods to control divergence of magnetic field, and time integrator. We then review on the state of art in numerical studies on solar active region, flares, prominences, and coronal rains.

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Heat flux saturation in hydrodynamic soft X-ray solar flare plasmas

Cited by 6 publications

References 11 publications

Self‐consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence

Self‐consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence

Mesoscale Phenomena during a Macroscopic Solar Eruption

Radiative magnetohydrodynamics simulations on solar corona

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