Modeling of Solar Flare Plasma and Its Radiation

Varady, M.; Kašparová, J.; Moravec, Zdeněk; Heinzel, P.; Karlický, M.

doi:10.1109/tps.2010.2057449

Cited by 26 publications

(18 citation statements)

References 15 publications

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“…From the modeling we found that the line cores are very sensitive to gas pressure in overlying coronal loops. In a future study we plan to perform more realistic radiative-hydrodynamical simulations of the temporal evolution of flare spectra using the code Flarix developed at the Ondřejov observatory (Varady et al, 2010). Electron-beam spectra derived from simultaneous RHESSI observations (see Kleint et al, 2015a) will be used.…”

Section: Discussionmentioning

confidence: 99%

Mg ii Lines Observed During the X-class Flare on 29 March 2014 by the Interface Region Imaging Spectrograph

Liu¹,

Heinzel²,

Kleint³

et al. 2016

Solar and Stellar Flares

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Mg ii lines represent one of the strongest emissions from the chromospheric plasma during solar flares. In this article, we studied the Mg ii lines observed during the X1 flare on March 29 2014 (SOL2014-03-29T17:48) by the Interface Region Imaging Spectrograph (IRIS). IRIS detected large intensity enhancements of the Mg ii h and k lines, subordinate triplet lines, and several other metallic lines at the flare footpoints during this flare. We have used the advantage of the slit-scanning mode (rastering) of IRIS and performed, for the first time, a detailed analysis of spatial and temporal variations of the spectra. Moreover, we were also able to identify positions of strongest hard X-ray (HXR) emissions using the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observations and to correlate them with the spatial and temporal evolution of IRIS Mg ii spectra. The light curves of the Mg ii lines increase and peak contemporarily with the HXR emissions but decay more gradually. There are large red asymmetries in the Mg ii h and k lines after the flare peak. We see two spatially well separated groups of Mg ii line profiles, non-reversed and reversed. In some cases, the Mg ii footpoints with reversed profiles are correlated with HXR sources. We show the spatial and temporal behavior of several other line parameters (line metrics) and briefly discuss them. Finally, we have synthesized the Mg ii k line using our non-LTE code with the Multilevel Accelerated Lambda Iteration (MALI) technique. Two kinds of models are considered, the flare model F2 of Machado et al. (1980, Astrophys. J., 242, 336 ) and the models of Ricchiazzi and Canfield (1983, Astrophys. J., 272, 739, RC). Model F2 reproduces the peak intensity of the unreversed Mg ii k profile at flare maximum but does not account for high wing intensities. On the other hand, the RC models show the sensitivity of Mg ii line intensities to various electronbeam parameters. Our simulations also show that the microturbulence produces a broader line core, while the intense line wings are caused by an enhanced line source function.

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Section: Discussionmentioning

confidence: 99%

Mg ii Lines Observed During the X-class Flare on 29 March 2014 by the Interface Region Imaging Spectrograph

Liu¹,

Heinzel²,

Kleint³

et al. 2016

Solar and Stellar Flares

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“…The hybrid radiation-hydrodynamical code Flarix is based on three originally autonomous, now within Flarix fully integrated, codes: a test-particle (TP) code, a onedimensional hydrodynamical (HD) code and time dependent NLTE radiative transfer code (for a detailed description of the code see Kašparová et al (2009) and Varady et al (2010)). Flarix is able to model several processes, which according to contemporary and generally accepted flare models occur concurrently in flares and play there important roles.…”

Section: Rhd Code Flarixmentioning

confidence: 99%

“…Recent advances in numerical RHD (radiation hydrodynamics) allow to solve complex problems of time evolution of the solar atmosphere affected by various flare processes (Allred et al 2005, Kašparová et al 2009, Varady et al 2010, Allred et al 2015. Resulting time-dependent atmospheric models (i.e.…”

Section: Introductionmentioning

confidence: 99%

Numerical RHD simulations of flaring chromosphere with Flarix

Heinzel¹,

Kašparová²,

Varady

et al. 2015

Proc. IAU

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Abstract. Flarix is a radiation-hydrodynamical (RHD) code for modeling of the response of the chromosphere to a beam bombardment during solar flares. It solves the set of hydrodynamic conservation equations coupled with NLTE equations of radiative transfer. The simulations are driven by high energy electron beams. We present results of the Flarix simulations of a flaring loop relevant to the problem of continuum radiation during flares. In particular we focus on properties of the hydrogen Balmer continuum which was recently detected by IRIS.

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“…The simulations presented in this work start with an injection of an initial electron beam into a closed magnetic loop at its summit point using a test-particle approach (Varady et al 2010). Physically, the initial beam represents a population of nonthermal electrons generated at the primary acceleration site located in the corona above the flare loop.…”

Section: Beam Properties and Target Atmospherementioning

confidence: 99%

“…Therefore it also influences the thermalisation rate of the non-thermal electrons (Emslie 1978;Kašparová et al 2009) and thus the outcome of the bombardment (Varady et al 2013). Using a hydrodynamic flare code combined with a test-particle code (Varady et al 2010), we tested the influence in increased temperature and change of ionisation due to the flare heating on the HXR spectra produced in the thick-target region and on the corresponding energy deposits. We found only relatively minor changes in comparison with the results for the quiet VAL C atmosphere.…”

Section: Beam Properties and Target Atmospherementioning

confidence: 99%

Modifications of thick-target model: re-acceleration of electron beams by static and stochastic electric fields

Varady

Karlický

Moravec

et al. 2014

A&A

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Context. The collisional thick-target model (CTTM) of the impulsive phase of solar flares, together with the famous Carmichael, Sturrock, Hirayama, and Kopp-Pneuman (CSHKP) model, presented for many years a "standard" model, which straightforwardly explained many observational aspects of flares. On the other hand, many critical issues appear when the concept is scrutinised theoretically or with the new generation of hard X-ray (HXR) observations. The famous "electron number problem" or problems related to transport of enormous particle fluxes though the corona represent only two of them. To resolve the discrepancies, several modifications of the CTTM appeared. Aims. We study two of them based on the global and local re-acceleration of non-thermal electrons by static and stochastic electric fields during their transport from the coronal acceleration site to the thick-target region in the chromosphere. We concentrate on a comparison of the non-thermal electron distribution functions, chromospheric energy deposits, and HXR spectra obtained for both considered modifications with the CTTM itself. Methods. The results were obtained using a relativistic test-particle approach. We simulated the transport of non-thermal electrons with a power-law spectrum including the influence of scattering, energy losses, magnetic mirroring, and also the effects of the electric fields corresponding to both modifications of the CTTM. Results. We show that both modifications of the CTTM change the outcome of the chromospheric bombardment in several aspects. The modifications lead to an increase in chromospheric energy deposit, change of its spatial distribution, and a substantial increase in the corresponding HXR spectrum intensity. Conclusions. The re-acceleration in both models reduces the demands on the efficiency of the primary coronal accelerator, on the electron fluxes transported from the corona downwards, and on the total number of accelerated coronal electrons during flares.

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Modeling of Solar Flare Plasma and Its Radiation

Cited by 26 publications

References 15 publications

Mg ii Lines Observed During the X-class Flare on 29 March 2014 by the Interface Region Imaging Spectrograph

Mg ii Lines Observed During the X-class Flare on 29 March 2014 by the Interface Region Imaging Spectrograph

Numerical RHD simulations of flaring chromosphere with Flarix

Modifications of thick-target model: re-acceleration of electron beams by static and stochastic electric fields

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