Effect of coronal elemental abundances on the radiative loss function

Cook, J. W.; Cheng, C. C.; Jacobs, V. L.; Antiochos, S. K.

doi:10.1086/167268

Cited by 128 publications

(86 citation statements)

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“…For the radiative loss function, Q(T ), we choose the form given by Cook et al (1989), calculated assuming photospheric abundance. Note also that we work in units where the universal gas constant equals the mean molecular weight.…”

Section: Basic Equationsmentioning

confidence: 99%

Physical consequences of the inclusion of anomalous resistivity in the dynamics of 2D magnetic reconnection

Roussev¹,

Galsgaard²,

Judge³

2002

A&A

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Abstract. The aim of the present paper is to explore the role of anomalous resistivity on the dynamics of magnetic reconnection in a 2D environment of relevance to the solar transition region. We adopt an ad hoc but explicit form of the anomalous resistivity, motivated by a streaming instability, in which the resistivity jumps suddenly as the electron drift velocity exceeds some fraction of the mean electron thermal speed. Experiments have been conducted to investigate the impact of various critical speeds and arbitrary scaling constants of the resistivity level on the time-dependent evolution of the magnetic reconnection process. The specific threshold value is found to influence the dynamics of the reconnection, with higher values providing a localised on-off effect of patchy diffusion. For a given normalised value of the anomalous resistivity, the amount of Joule heating released scales inversely with the threshold value. The total energy release is found to be above the lower limit of "quiet" Sun nano-flares required to maintain a hot corona. The reconnection events discussed here may be important to the energy balance of the solar transition region and overlying corona, as already suggested in earlier work based on SUMER observations.

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Section: Basic Equationsmentioning

confidence: 99%

Physical consequences of the inclusion of anomalous resistivity in the dynamics of 2D magnetic reconnection

Roussev¹,

Galsgaard²,

Judge³

2002

A&A

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“…The general loss rate by thermal emission, R, was described by an optically thin plasma approximated by Cook et al (1989) as…”

Section: Methodsmentioning

confidence: 99%

Nonlocal heat flux effects on temperature evolution of the solar atmosphere

Silva

Santos

Büchner

et al. 2018

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Context. Heat flux is one of the main energy transport mechanisms in the weakly collisional plasma of the solar corona. There, rare binary collisions let hot electrons travel over long distances and influence other regions along magnetic field lines. Thus, the fully collisional heat flux models might not describe transport well enough since they consider only the local contribution of electrons. The heat flux in weakly collisional plasmas at high temperatures with large mean free paths has to consider the nonlocality of the energy transport in the frame of nonlocal models in order to treat energy balance in the solar atmosphere properly. Aims. We investigate the impact of nonlocal heat flux on the thermal evolution and dynamics of the solar atmosphere by implementing a nonlocal heat flux model in a 3D magnetohydrodynamic simulation of the solar corona. Methods. We simulate the evolution of solar coronal plasma and magnetic fields considering both a local collision dominated and a nonlocal heat flux model. The initial magnetic field is obtained by a potential extrapolation of the observed line-of-sight magnetic field of AR11226. The system is perturbed by moving the plasma at the photosphere. We compared the simulated evolution of the solar atmosphere in its dependence on the heat flux model. Results. The main differences for the average temperature profiles were found in the upper chromosphere/transition region. In the nonlocal heat transport model case, thermal energy is transported more efficiently to the upper chromosphere and lower transition region and leads to an earlier heating of the lower atmosphere. As a consequence, the structure of the solar atmosphere is affected with the nonlocal simulations producing on average a smoother temperature profile and the transition region placed about 500 km higher. Using a nonlocal heat flux also leads to two times higher temperatures in some of the regions in the lower corona. Conclusions. The results of our 3D MHD simulations considering nonlocal heat transport supports the previous results of simpler 1D two-fluid simulations. They demonstrated that it is important to consider a nonlocal formulation for the heat flux when there is a strong energy deposit, like the one observed during flares, in the solar corona.

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“…1. Radiative-loss functions from the works of Cook et al (1989), Golub & Pasachoff (1997), Martens et al (2000), Klimchuk et al (2008), and radiative-loss function as given by CHIANTI v5.2 (Landi et al 2006). Parametric fits by Kuin & Martens (1982) and Rosner et al (1978) are also displayed.…”

Section: Introductionmentioning

confidence: 99%

“…The radiative losses as the function of temperature and electron density have been computed for solar plasma by a number of authors using different sets of atomic data and abundances (e.g., Tucker & Koren 1971;McWhirter et al 1975;Cook et al 1989;Landi & Landini 1999;Martens et al 2000;Landi et al 2006;Colgan et al 2008;Dere et al 2009), but all of these works assume the presence of Maxwellian distribution. A sample of them is shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

The bound-bound and free-free radiative losses for the nonthermal distributions in solar and stellar coronae

Dudík

Dzifčáková

Karlický

et al. 2011

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Context. The radiative-loss function is an important ingredient in the physics of the solar corona, transition region, and flares. Aims. We investigate the radiative losses due to the bound-bound transitions and bremsstrahlung for nonthermal κ-and n-distributions. Methods. The bound-bound radiative losses are computed by integrating synthetic spectra. An analytical expression is derived for nonthermal bremsstrahlung. The bremsstrahlung is computed numerically using accurate values of the free-free Gaunt factor. Results. We find that the changes in radiative-loss functions due to nonthermal distributions are several times greater than the errors due to the missing contribution of the free-bound continuum or errors in atomic data. For κ-distributions, the radiative-loss functions are in general weaker than for Maxwellian distribution, with a few exceptions caused by the behavior of Fe. The peaks of the radiativeloss functions are in general flatter. The situation is opposite for n-distributions, for which the radiative-loss functions have higher and narrower peaks. Local minima and maxima of the radiative-loss functions may also be shifted. The contribution from bremsstrahlung only changes by a few percent except in the extreme nonthermal case of κ = 2. Stability analysis reveals that the X-ray loops are stable against the radiatively-driven thermal instability.

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Effect of coronal elemental abundances on the radiative loss function

Cited by 128 publications

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Physical consequences of the inclusion of anomalous resistivity in the dynamics of 2D magnetic reconnection

Physical consequences of the inclusion of anomalous resistivity in the dynamics of 2D magnetic reconnection

Nonlocal heat flux effects on temperature evolution of the solar atmosphere

The bound-bound and free-free radiative losses for the nonthermal distributions in solar and stellar coronae

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