Extreme‐Ultraviolet Transition‐Region Line Emission during the Dynamic Formation of Prominence Condensations

2001 ◽  
Vol 547 (2) ◽  
pp. 1116-1129 ◽  
Author(s):  
Antonino F. Lanza ◽  
Daniele Spadaro ◽  
Alessandro C. Lanzafame ◽  
Spiro K. Antiochos ◽  
Peter J. MacNeice ◽  
...  
Keyword(s):  
Transition Region ◽  
Extreme Ultraviolet ◽  
Line Emission ◽  
Dynamic Formation ◽  
Region Line

The relation between hard X-ray and transition-region line emission in solar flares

Solar Physics ◽  
1985 ◽  
Vol 96 (2) ◽  
pp. 317-330 ◽  
Author(s):  
John T. Mariska ◽  
A. I. Poland
Keyword(s):  
Transition Region ◽  
Solar Flares ◽  
Line Emission ◽  
X Ray ◽  
Region Line

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.

scholarly journals Hot prominence spicules launched from turbulent cool solar prominences

2019 ◽  
Vol 627 ◽  
pp. L5 ◽  
Author(s):  
L. P. Chitta ◽  
H. Peter ◽  
L. Li
Keyword(s):  
Transition Region ◽  
Extreme Ultraviolet ◽  
The Sun ◽  
Solar Dynamics Observatory ◽  
Solar Prominences ◽  
Solar Filament ◽  
Solar Dynamics ◽  
Ultraviolet Observations ◽  
Hot Corona ◽  
Shed Light

A solar filament is a dense cool condensation that is supported and thermally insulated by magnetic fields in the rarefied hot corona. Its evolution and stability, leading to either an eruption or disappearance, depend on its coupling with the surrounding hot corona through a thin transition region, where the temperature steeply rises. However, the heating and dynamics of this transition region remain elusive. We report extreme-ultraviolet observations of quiescent filaments from the Solar Dynamics Observatory that reveal prominence spicules propagating through the transition region of the filament-corona system. These thin needle-like jet features are generated and heated to at least 0.7 MK by turbulent motions of the material in the filament. We suggest that the prominence spicules continuously channel the heated mass into the corona and aid in the filament evaporation and decay. Our results shed light on the turbulence-driven heating in magnetized condensations that are commonly observed on the Sun and in the interstellar medium.

scholarly journals Reappraising Transition Region Line Widths in Light of Recent Alfvén Wave Discoveries

2008 ◽  
Vol 673 (2) ◽  
pp. L219-L223 ◽  
Author(s):  
Scott W. McIntosh ◽  
Bart De Pontieu ◽  
Theodore D. Tarbell
Keyword(s):  
Transition Region ◽  
Alfven Wave ◽  
Line Widths ◽  
Region Line

scholarly journals Dissecting the EUV Spectrum of Capella

1996 ◽  
Vol 152 ◽  
pp. 105-112 ◽  
Author(s):  
Nancy S. Brickhouse
Keyword(s):  
Extreme Ultraviolet ◽  
Emission Measure ◽  
Continuous Distribution ◽  
Line Emission ◽  
Local Maximum ◽  
Abundance Ratio ◽  
Emission Lines ◽  
Cool Star ◽  
The Individual ◽  
The Continuum

Extreme ultraviolet spectra of Capella, obtained at various orbital phases over the past two years by the EUVE satellite, show strong emission lines from a continuous distribution of temperatures (~ 105 − 107.3 K). In addition to the strong He II λ303.8, the spectra are dominated by emission lines of highly ionized iron. Strong lines of Fe IX, XV, XVI, and XVIII–XXIV are used to construct emission measure distributions for the individual pointings, which show several striking features, including a minimum near 106 K and a local maximum at 106.8 K. Furthermore, intensities of the highest temperature lines (Te > 107 K) show variations (factors of 2–3) at different orbital phases, while the lower temperature Fe lines show variations of about 30% or less. The low variability of most of the strong low temperature features motivates a detailed analysis of the summed spectrum. With ~ 280 ks of total exposure time, we have measured over 200 emission features with S/N ≥ 3.0 in the summed spectrum. We report here initial results from the analysis of this spectrum. We can now identify lines of Fe VIII and X–XIV, as well as a number of electron density and abundance diagnostic lines.We also report here the first direct measurement of the continuum flux around ~ 100 Å in a cool star atmosphere with EUVE. The continuum flux can be predicted from the emission measure model based on Fe line emission, and demonstrates that the Fe/H abundance ratio is close to the solar photospheric value.

scholarly journals Experiment to Determine the Temperature Structure in the Solar Chromosphere and Corona

1972 ◽  
Vol 14 ◽  
pp. 668-669
Author(s):  
C. R. Negus
Keyword(s):  
Transition Region ◽  
Extreme Ultraviolet ◽  
Normal Incidence ◽  
Research Unit ◽  
Emission Lines ◽  
Solar Chromosphere ◽  
Temperature Structure ◽  
Ultraviolet Emission ◽  
Ionization Temperature ◽  
Intensity Ratios

An experiment is in course of preparation at the Astrophysics Research Unit at Culham for flight on a Sun-pointing rocket. It is designed to determine the ionization temperature and electron density as a function of height in the temperature range of about 8 × 104 K to 3 × 106 K by measuring limb to disk intensity ratios of extreme ultraviolet emission lines in the 170 to 850 Å region. The work is an extension of current experiments in which normal-incidence spectrographs are used to determine the structure lower in the chromosphere-corona transition region.

Transition region line-shifts in the rebound shock spicule model

1994 ◽  
Vol 70 (1-2) ◽  
pp. 103-106 ◽  
Author(s):  
V. H. Hansteen ◽  
�. Wikst�l
Keyword(s):  
Transition Region ◽  
Region Line

Helium line emission: its relation to atmospheric structure

1980 ◽  
Vol 297 (1433) ◽  
pp. 541-554 ◽  
Keyword(s):  
Temperature Gradient ◽  
Transition Region ◽  
Scaling Laws ◽  
Coronal Holes ◽  
Emission Measure ◽  
Line Emission ◽  
Electron Pressure ◽  
Steep Temperature Gradient ◽  
Region Temperature ◽  
Higher Temperature

A brief review is given of observations of the resonance lines of He I and He II and their interpretation. As discussed in a previous paper, the helium lines are anomalously strong in the quiet Sun when compared with other transition region lines. The enhancement can be brought about by the transient excitation of the lines by electrons of higher temperature than that which determines the ion population. The variation in the intensity of the helium lines relative to those of other transition region lines appears to be related to variations in the temperature gradient between different parts of the atmosphere. To relate the degree of enhancement to other observable parameters, such as electron pressure and absolute line intensities, and thus to the structure of the atmosphere, a method for analysing the emission measure distribution previously developed in the context of the quiet atmosphere and active region loops is applied also to coronal holes. It is proposed that the non-thermal ion motions observed in the transition region can provide the required mechanism for transporting the helium ions across the steep temperature gradient. By making a simple model, an expression is developed which relates the helium enhancement to the non-thermal motions, the transition region temperature gradient and the electron pressure. The scaling laws implied can be tested against further observations when they become available.

scholarly journals Observation of Quasi-Continuum Line Emission from F[CLC]e[/CLC] [CSC]vii[/CSC] to F[CLC]e[/CLC] [CSC]x[/CSC] in the Extreme-Ultraviolet Region below 140 Å

1999 ◽  
Vol 519 (2) ◽  
pp. L185-L188 ◽  
Author(s):  
P. Beiersdorfer ◽  
J. K. Lepson ◽  
G. V. Brown ◽  
S. B. Utter ◽  
S. M. Kahn ◽  
...  
Keyword(s):  
Extreme Ultraviolet ◽  
Line Emission ◽  
Ultraviolet Region
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