Efficient Calculation of Non-local Thermodynamic Equilibrium Effects in Multithreaded Hydrodynamic Simulations of Solar Flares

Abstract

Understanding the dynamics of the solar chromosphere is crucial to understanding energy transport across the solar atmosphere. The chromosphere is optically thick at many wavelengths and described by non-local thermodynamic equilibrium (NLTE), making it difficult to interpret observations. Furthermore, there is considerable evidence that the atmosphere is filamented, and that current instruments do not sufficiently resolve small scale features. In flares, it is likely that multithreaded models are required to describe the heating. The combination of NLTE effects and multithreaded modeling requires computationally demanding calculations, which has motivated the development of a model that can efficiently treat both. We describe the implementation of a solver in a hydrodynamic code for the hydrogen level populations that approximates the NLTE solutions. We derive an accurate electron density across the atmosphere, that includes the effects of non-equilibrium ionization for helium and metals. We show the effects on hydrodynamic simulations, which are used to synthesize light curves using a post-processing radiative transfer code. We demonstrate the utility of this model on IRIS observations of a small flare. We show that the Doppler shifts in Mg II, C II, and O I can be explained with a multithreaded model of loops subjected to electron beam heating, so long as NLTE effects are treated. The intensities, however, do not match observed values very well, which is due to assumptions about the initial atmosphere. We briefly show how altering the initial atmosphere can drastically alter line profiles, and therefore derived quantities, and suggest that it should be tuned to pre-flare observations.

The expansion of the Universe may be an illusion created by Compton scattering of free electrons

“…The electron density of the flare was in the range of 12 10 - 14 -3 10 cm , log (k) e T  4-4.5 31,32 , the value of K was roughly estimated around…”

“…The redshift asymmetry rules out the Stark effect because Stark-induced shift occurs in dense plasma (plasma with electron concentration about and above 16 -3 10 cm 30 ). The electron density of solar flares is generally in the range of 12 10 -14 -3 10 cm 31,32 . When solar flares occur, the temperature of the solar atmosphere increases and ionization increases.…”

“…10 cm 30 ). The electron density of solar flares is generally in the range of 12 10 -14 -3 10 cm 31,32 . When solar flares occur, the temperature of the solar atmosphere increases and ionization increases.…”

Free electron Compton scattering produces the illusion of the universe expansion

“…When solar flares occur, their spectral profile has a redshift asymmetry 27,28,29 that is difficult to explain with the Doppler effect, and the redshift asymmetry rules out the Stark effect because Stark-induced shift occurs in dense plasma (plasma with electron concentration about and above 16 -3 10 cm 30 ). The electron density of solar flares is generally in the range of 12 14 -3 10 10 cm : 31,32 . Since the FEC and Doppler effects are independent of the wavelength, it is sometimes difficult to distinguish them.…”

The expansion of the Universe may be an illusion created by Compton scattering of free electrons

“…The redshift asymmetry rules out the Stark effect because Stark-induced shift occurs in dense plasma (plasma with electron concentration about and above 16 -3 10 cm 30 ). The electron density of solar flares is generally in the range of 12 14 -3 10 10 cm 31,32 . When solar flares occur, the temperature of the solar atmosphere increases and ionization increases.…”