Forward Modeling of the Corona of the Sun and Solar‐like Stars: From a Three‐dimensional Magnetohydrodynamic Model to Synthetic Extreme‐Ultraviolet Spectra

2006 ◽  
Vol 638 (2) ◽  
pp. 1086-1100 ◽  
Author(s):  
Hardi Peter ◽  
Boris V. Gudiksen ◽  
Ake Nordlund
Keyword(s):  
Extreme Ultraviolet ◽  
Three Dimensional ◽  
Forward Modeling ◽  
The Sun ◽  
Ultraviolet Spectra ◽  
Magnetohydrodynamic Model ◽  
Corona Of The Sun

scholarly journals What can large-scale magnetohydrodynamic numerical experiments tell us about coronal heating?

2015 ◽  
Vol 373 (2042) ◽  
pp. 20150055 ◽  
Author(s):  
H. Peter
Keyword(s):  
Magnetic Field ◽  
Numerical Experiments ◽  
Large Scale ◽  
Extreme Ultraviolet ◽  
Complex Structure ◽  
Three Dimensional ◽  
Upper Atmosphere ◽  
Good Representation ◽  
The Sun ◽  
Coronal Emission

The upper atmosphere of the Sun is governed by the complex structure of the magnetic field. This controls the heating of the coronal plasma to over a million kelvin. Numerical experiments in the form of three-dimensional magnetohydrodynamic simulations are used to investigate the intimate interaction between magnetic field and plasma. These models allow one to synthesize the coronal emission just as it would be observed by real solar instrumentation. Large-scale models encompassing a whole active region form evolving coronal loops with properties similar to those seen in extreme ultraviolet light from the Sun, and reproduce a number of average observed quantities. This suggests that the spatial and temporal distributions of the heating as well as the energy distribution of individual heat deposition events in the model are a good representation of the real Sun. This provides evidence that the braiding of fieldlines through magneto-convective motions in the photosphere is a good concept to heat the upper atmosphere of the Sun.

scholarly journals Review of ground-based observations of spectra relevant to the ultraviolet

1970 ◽  
Vol 36 ◽  
pp. 187-198
Author(s):  
M. W. Feast
Keyword(s):  
Mass Loss ◽  
Extreme Ultraviolet ◽  
The Sun ◽  
Temperature Minimum ◽  
Early Type ◽  
Ultraviolet Spectra ◽  
Early Type Stars

Up to the present the chief results of investigations of stellar line spectra in the extreme ultraviolet have been limited to two fairly distinct fields. In the case of the Sun the data have referred mainly to the chromosphere and also to the region of the temperature minimum at the top of the photosphere and to the corona. We may hope that observations will eventually be extended to the chromospheric ultraviolet spectra of other stars. In the case of the early type stars the most spectacular results so far obtained have concerned the evidence for mass loss by several of these stars. I have therefore chosen to spend most of the available time discussing some of the ways of studying from the ground, first the chromospheres of stars other than the Sun and secondly mass loss from stars.

scholarly journals Energetics of magnetic transients in a solar active region plage

2019 ◽  
Vol 623 ◽  
pp. A176 ◽  
Author(s):  
L. P. Chitta ◽  
A. R. C. Sukarmadji ◽  
L. Rouppe van der Voort ◽  
H. Peter
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Magnetic Flux ◽  
Numerical Simulations ◽  
Extreme Ultraviolet ◽  
Spatial Scales ◽  
Coronal Loops ◽  
The Sun ◽  
Flux Emergence ◽  
Transient Events

Context. Densely packed coronal loops are rooted in photospheric plages in the vicinity of active regions on the Sun. The photospheric magnetic features underlying these plage areas are patches of mostly unidirectional magnetic field extending several arcsec on the solar surface. Aims. We aim to explore the transient nature of the magnetic field, its mixed-polarity characteristics, and the associated energetics in the active region plage using high spatial resolution observations and numerical simulations. Methods. We used photospheric Fe I 6173 Å spectropolarimetric observations of a decaying active region obtained from the Swedish 1-m Solar Telescope (SST). These data were inverted to retrieve the photospheric magnetic field underlying the plage as identified in the extreme-ultraviolet emission maps obtained from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). To obtain better insight into the evolution of extended unidirectional magnetic field patches on the Sun, we performed 3D radiation magnetohydrodynamic simulations of magnetoconvection using the MURaM code. Results. The observations show transient magnetic flux emergence and cancellation events within the extended predominantly unipolar patch on timescales of a few 100 s and on spatial scales comparable to granules. These transient events occur at the footpoints of active region plage loops. In one case the coronal response at the footpoints of these loops is clearly associated with the underlying transient. The numerical simulations also reveal similar magnetic flux emergence and cancellation events that extend to even smaller spatial and temporal scales. Individual simulated transient events transfer an energy flux in excess of 1 MW m−2 through the photosphere. Conclusions. We suggest that the magnetic transients could play an important role in the energetics of active region plage. Both in observations and simulations, the opposite-polarity magnetic field brought up by transient flux emergence cancels with the surrounding plage field. Magnetic reconnection associated with such transient events likely conduits magnetic energy to power the overlying chromosphere and coronal loops.

Experimental and simulation study of impurity transport response to RMPs in RF-heated H-mode plasmas at EAST

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Germán Vogel ◽  
Hongming Zhang ◽  
Yongcai Shen ◽  
Shuyu Dai ◽  
Youwen Sun ◽  
...  
Keyword(s):  
Inner Core ◽  
Extreme Ultraviolet ◽  
Transport Coefficients ◽  
Three Dimensional ◽  
Line Emission ◽  
Core Region ◽  
Emission Mitigation ◽  
One Dimensional ◽  
Impurity Transport ◽  
Transport Code

Spatial profiles of impurity emission measurements in the extreme ultraviolet (EUV) spectroscopic range in radiofrequency (RF)-heated discharges are combined with one-dimensional and three-dimensional transport simulations to study the effects of resonant magnetic perturbations (RMPs) on core impurity accumulation at EAST. The amount of impurity line emission mitigation by RMPs appears to be correlated with the ion Z for lithium, carbon, iron and tungsten monitored, i.e. stronger suppression of accumulation for heavier ions. The targeted effect on the most detrimental high-Z impurities suggests a possible advantage using RMPs for impurity control. Profiles of transport coefficients are calculated with the STRAHL one-dimensional impurity transport code, keeping $\nu /D$ fixed and using the measured spatial profiles of $\textrm{F}{\textrm{e}^{20 + }}$ , $\textrm{F}{\textrm{e}^{21 + }}$ and $\textrm{F}{\textrm{e}^{22 + }}$ to disentangle the transport coefficients. The iron diffusion coefficient ${D_{\textrm{Fe}}}$ increases from $1.0- 2.0\;{\textrm{m}^2}\;{\textrm{s}^{ - 1}}$ to $1.5- 3.0\;{\textrm{m}^2}\;{\textrm{s}^{ - 1}}$ from the core region to the edge region $(\rho \gt 0.5)$ after the onset of RMPs. Meanwhile, an inward pinch of iron convective velocity ${\nu _{\textrm{Fe}}}$ decreases in magnitude in the inner core region and increases significantly in the outer confined region, simultaneously contributing to preserving centrally peaked $\textrm{Fe}$ profiles and exhausting the impurities. The ${D_{\textrm{Fe}}}$ and ${\nu _{\textrm{Fe}}}$ variations lead to reduced impurity contents in the plasma. The three-dimensional edge impurity transport code EMC3-EIRENE was also applied for a case of RMP-mitigated high-Z accumulation at EAST and compared to that of low-Z carbon. The exhaust of ${\textrm{C}^{6 + }}$ toward the scrape-off layer accompanying an overall suppression of heavier ${\textrm{W}^{30 + }}$ is observed when using RMPs.

The Corona of the Sun

1899 ◽  
Vol 17 ◽  
pp. 210
Author(s):  
Ephraim Miller
Keyword(s):  
The Sun ◽  
Corona Of The Sun

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.

scholarly journals Magnetic jam in the corona of the Sun

2015 ◽  
Vol 11 (6) ◽  
pp. 492-495 ◽  
Author(s):  
F. Chen ◽  
H. Peter ◽  
S. Bingert ◽  
M. C. M. Cheung
Keyword(s):  
The Sun ◽  
Corona Of The Sun

scholarly journals Three‐dimensional Numerical Simulations of the Acoustic Wave Field in the Upper Convection Zone of the Sun

2007 ◽  
Vol 666 (1) ◽  
pp. 547-558 ◽  
Author(s):  
K. V. Parchevsky ◽  
A. G. Kosovichev
Keyword(s):  
Acoustic Wave ◽  
Numerical Simulations ◽  
Wave Field ◽  
Convection Zone ◽  
Three Dimensional ◽  
The Sun

scholarly journals Measurements of the effective electron density in an electron beam ion trap using extreme ultraviolet spectra and optical imaging

2018 ◽  
Vol 89 (10) ◽  
pp. 10E119 ◽  
Author(s):  
T. P. Arthanayaka ◽  
P. Beiersdorfer ◽  
G. V. Brown ◽  
M. Hahn ◽  
N. Hell ◽  
...  
Keyword(s):  
Electron Beam ◽  
Optical Imaging ◽  
Electron Density ◽  
Ion Trap ◽  
Extreme Ultraviolet ◽  
Effective Electron ◽  
Ultraviolet Spectra ◽  
Electron Beam Ion Trap
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