Temperature diagnostics of plasma under optically-thin conditions

2017 ◽  
Vol 31 (31) ◽  
pp. 1750292
Author(s):  
Zhiqiang Zhen ◽  
Jian He
Keyword(s):  
Intensity Ratio ◽  
Equilibrium Temperature ◽  
Spectral Lines ◽  
Ionization Equilibrium ◽  
Average Cell ◽  
Quiet Sun ◽  
Solar Transition Region ◽  
Solar Transition ◽  
Temperature Diagnostics ◽  
Good Agreement

For temperature diagnostics of plasma, using the silicon spectral lines emitted from the solar transition region, under the optically-thin conditions, we discuss temperature diagnostics of the quiet sun in some typical features. For the silicon IV 112.8325 nm and 140.2770 nm spectral lines, using the observed intensity ratio, we calculate the temperature of faint cell center, average cell center, average quiet sun, average network, bright network and very bright network of the quiet sun, and results are in good agreement with those predicted at the [Formula: see text] ionization equilibrium temperature of formation of the silicon IV, and we discuss the temperature when the observed intensity varies from 0.05 to 0.2. This investigation will be significant for temperature diagnostics of plasma under the optically-thin conditions.

Si III electron temperature diagnostics for the solar transition region

Solar Physics ◽  
1989 ◽  
Vol 123 (1) ◽  
pp. 33-39 ◽  
Author(s):  
F. P. Keenan ◽  
P. L. Dufton ◽  
A. E. Kingston
Keyword(s):  
Electron Temperature ◽  
Transition Region ◽  
Solar Transition Region ◽  
Solar Transition ◽  
Temperature Diagnostics

scholarly journals SUMER Observations of the Solar Transition Region: Spatial and Temporal Behaviour

2001 ◽  
Vol 203 ◽  
pp. 425-427
Author(s):  
L. Teriaca ◽  
J. G. Doyle ◽  
D. Banerjee
Keyword(s):  
High Resolution ◽  
Wavelet Analysis ◽  
Transition Region ◽  
Line Width ◽  
Doppler Shift ◽  
Temporal Behaviour ◽  
Quiet Sun ◽  
Solar Transition Region ◽  
Solar Transition ◽  
Width Measurements

We examine the spatial and temporal behaviour of the quiet Sun transition region (TR) using high resolution SUMER observations in O VI 1032 Å. A detailed study of raster images allows us to differentiate the network and internetwork through Doppler shift and line width measurements. The oscillatory nature of the TR is investigated using wavelet analysis over a series of spectra obtained with high temporal cadence.

scholarly journals Disentangling flows in the solar transition region

2018 ◽  
Vol 614 ◽  
pp. A110 ◽  
Author(s):  
P. Zacharias ◽  
V. H. Hansteen ◽  
J. Leenaarts ◽  
M. Carlsson ◽  
B. V. Gudiksen
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Transition Region ◽  
Magnetic Field Line ◽  
Spectral Lines ◽  
Continuous Heating ◽  
Solar Transition Region ◽  
Solar Transition ◽  
Energy Flows ◽  
The Magnetic Field

Context. The measured average velocities in solar and stellar spectral lines formed at transition region temperatures have been difficult to interpret. The dominant redshifts observed in the lower transition region naturally leads to the question of how the upper layers of the solar (and stellar) atmosphere can be maintained. Likewise, no ready explanation has been made for the average blueshifts often found in upper transition region lines. However, realistic three-dimensional radiation magnetohydrodynamics (3D rMHD) models of the solar atmosphere are able to reproduce the observed dominant line shifts and may thus hold the key to resolve these issues. Aims. These new 3D rMHD simulations aim to shed light on how mass flows between the chromosphere and corona and on how the coronal mass is maintained. These simulations give new insights into the coupling of various atmospheric layers and the origin of Doppler shifts in the solar transition region and corona. Methods. The passive tracer particles, so-called corks, allow the tracking of parcels of plasma over time and thus the study of changes in plasma temperature and velocity not only locally, but also in a co-moving frame. By following the trajectories of the corks, we can investigate mass and energy flows and understand the composition of the observed velocities. Results. Our findings show that most of the transition region mass is cooling. The preponderance of transition region redshifts in the model can be explained by the higher percentage of downflowing mass in the lower and middle transition region. The average upflows in the upper transition region can be explained by a combination of both stronger upflows than downflows and a higher percentage of upflowing mass. The most common combination at lower and middle transition region temperatures are corks that are cooling and traveling downward. For these corks, a strong correlation between the pressure gradient along the magnetic field line and the velocity along the magnetic field line has been observed, indicating a formation mechanism that is related to downward propagating pressure disturbances. Corks at upper transition region temperatures are subject to a rather slow and highly variable but continuous heating process. Conclusions. Corks are shown to be an essential tool in 3D rMHD models in order to study mass and energy flows. We have shown that most transition region plasma is cooling after having been heated slowly to upper transition region temperatures several minutes before. Downward propagating pressure disturbances are identified as one of the main mechanisms responsible for the observed redshifts at transition region temperatures.

REDSHIFTS, WIDTHS, AND RADIANCES OF SPECTRAL LINES EMITTED BY THE SOLAR TRANSITION REGION

2011 ◽  
Vol 743 (2) ◽  
pp. 165 ◽  
Author(s):  
U. Feldman ◽  
I. E. Dammasch ◽  
G. A. Doschek
Keyword(s):  
Transition Region ◽  
Spectral Lines ◽  
Solar Transition Region ◽  
Solar Transition

scholarly journals Quiet Sun electron densities and their uncertainties derived from spectral emission line intensities

2020 ◽  
Vol 496 (2) ◽  
pp. 2334-2345
Author(s):  
Kenneth P Dere
Keyword(s):  
Extreme Ultraviolet ◽  
Visual Assessment ◽  
Spectral Lines ◽  
Robust Estimate ◽  
Quiet Sun ◽  
Line Intensities ◽  
Statistical Confidence ◽  
Best Fitting ◽  
Sensitive Line ◽  
Good Agreement

ABSTRACT The goal of this paper is to apply statistical methods to determine electrons densities and their errors from measurements of density-sensitive line intensities in the quiet Sun. Three methods are employed. The first is the use of L-function plots to provide a quick visual assessment of the likelihood that a set of line intensities can provide a robust estimate of these quantities. A second methods involves a χ2 minimization together with a prescription for determining the regions of statistical confidence in addition to the best-fitting value. A third method uses a Bayesian inference technique that employs a Monte Carlo Markov Chain (MCMC) calculation from which an analysis of the posterior distributions provide estimates of the mean and regions of high probability density. Using these three methods, observations of extreme-ultraviolet spectral lines originating from regions of the quiet Sun have been analysed. The quantitative χ2 minimization and MCMC sampling provide results that are generally in good agreement, especially for sets of lines of ions that have L-function plots that suggest that a robust analysis might be possible.

scholarly journals Statistical Study of Network Jets Observed in the Solar Transition Region: a Comparison Between Coronal Holes and Quiet-Sun Regions

Solar Physics ◽  
2016 ◽  
Vol 291 (4) ◽  
pp. 1129-1142 ◽  
Author(s):  
Nancy Narang ◽  
Rebecca T. Arbacher ◽  
Hui Tian ◽  
Dipankar Banerjee ◽  
Steven R. Cranmer ◽  
...  
Keyword(s):  
Transition Region ◽  
Statistical Study ◽  
Coronal Holes ◽  
Quiet Sun ◽  
Solar Transition Region ◽  
Solar Transition

scholarly journals The relationship between photometric and spectroscopic oscillation amplitudes from 3D stellar atmosphere simulations

2021 ◽  
Author(s):  
Yixiao Zhou ◽  
Thomas Nordlander ◽  
Luca Casagrande ◽  
Meridith Joyce ◽  
Yaguang Li ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Three Dimensional ◽  
Quantitative Relationship ◽  
Stellar Atmospheres ◽  
Spectral Lines ◽  
Wavelength Shift ◽  
The Sun ◽  
Theoretical Derivation ◽  
Velocity Amplitude ◽  
Good Agreement

Abstract We establish a quantitative relationship between photometric and spectroscopic detections of solar-like oscillations using ab initio, three-dimensional (3D), hydrodynamical numerical simulations of stellar atmospheres. We present a theoretical derivation as proof of concept for our method. We perform realistic spectral line formation calculations to quantify the ratio between luminosity and radial velocity amplitude for two case studies: the Sun and the red giant ε Tau. Luminosity amplitudes are computed based on the bolometric flux predicted by 3D simulations with granulation background modelled the same way as asteroseismic observations. Radial velocity amplitudes are determined from the wavelength shift of synthesized spectral lines with methods closely resembling those used in BiSON and SONG observations. Consequently, the theoretical luminosity to radial velocity amplitude ratios are directly comparable with corresponding observations. For the Sun, we predict theoretical ratios of 21.0 and 23.7 ppm/[m s−1] from BiSON and SONG respectively, in good agreement with observations 19.1 and 21.6 ppm/[m s−1]. For ε Tau, we predict K2 and SONG ratios of 48.4 ppm/[m s−1], again in good agreement with observations 42.2 ppm/[m s−1], and much improved over the result from conventional empirical scaling relations which gives 23.2 ppm/[m s−1]. This study thus opens the path towards a quantitative understanding of solar-like oscillations, via detailed modelling of 3D stellar atmospheres.

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