A burst model for line emission in the solar atmosphere. II - Coronal extreme ultraviolet lines

1992 ◽  
Vol 398 ◽  
pp. 692 ◽  
Author(s):  
U. Feldman ◽  
J. M. Laming ◽  
P. Mandelbaum ◽  
W. H. Goldstein ◽  
A. Osterheld
Keyword(s):  
Solar Atmosphere ◽  
Extreme Ultraviolet ◽  
Line Emission

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 Height Structure of the Solar Atmosphere from the Extreme-Ultraviolet Perspective

1998 ◽  
Vol 504 (2) ◽  
pp. L127-L130 ◽  
Author(s):  
J. Zhang ◽  
S. M. White ◽  
M. R. Kundu
Keyword(s):  
Solar Atmosphere ◽  
Extreme Ultraviolet

The Sun

2015 ◽  
Author(s):  
Joanna D. Haigh ◽  
Peter Cargill
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Atmosphere ◽  
Space Weather ◽  
Extreme Ultraviolet ◽  
The Sun ◽  
Base Level ◽  
Earth’S Climate ◽  
The Magnetic Field ◽  
Terrestrial Magnetic Field

This chapter discusses how there are four general factors that contribute to the Sun's potential role in variations in the Earth's climate. First, the fusion processes in the solar core determine the solar luminosity and hence the base level of radiation impinging on the Earth. Second, the presence of the solar magnetic field leads to radiation at ultraviolet (UV), extreme ultraviolet (EUV), and X-ray wavelengths which can affect certain layers of the atmosphere. Third, the variability of the magnetic field over a 22-year cycle leads to significant changes in the radiative output at some wavelengths. Finally, the interplanetary manifestation of the outer solar atmosphere (the solar wind) interacts with the terrestrial magnetic field, leading to effects commonly called space weather.

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 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

Extreme ultraviolet line emission at 24.7 nm from Li‐like nitrogen plasma produced by a short KrF excimer laser pulse

1996 ◽  
Vol 69 (7) ◽  
pp. 884-886 ◽  
Author(s):  
N. S. Kim ◽  
A. Djaoui ◽  
M. H. Key ◽  
D. Neely ◽  
S. G. Preston ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Excimer Laser ◽  
Extreme Ultraviolet ◽  
Line Emission ◽  
Nitrogen Plasma ◽  
Excimer Laser Pulse ◽  
Krf Excimer Laser

scholarly journals Solar EUV Photoelectric Observations from Skylab

1974 ◽  
Vol 57 ◽  
pp. 497-500
Author(s):  
E. M. Reeves ◽  
P. V. Foukal ◽  
M. C. E. Huber ◽  
R. W. Noyes ◽  
E. J. Schmahl ◽  
...  
Keyword(s):  
Solar Atmosphere ◽  
Extreme Ultraviolet ◽  
Three Dimensional ◽  
Active Regions ◽  
Normal Incidence ◽  
Ionic Species ◽  
Ultraviolet Region ◽  
Spatial Image ◽  
Lyman Continuum ◽  
Solar Blind

Most of the atomic species originating in the solar atmosphere between the upper chromosphere and the corona have their strong characteristic wavelengths in the extreme ultraviolet region of the spectrum. A simple normal-incidence spectrometer system with solar blind detectors such as the Harvard instrument operating between approximately 250 Å and 1350 Å is ideally suited for observing in this most interesting range of the solar atmosphere where the temperature rises outward from 104 to 3 × 106 K. The temperature range represented by the various atomic and ionic species in the extreme ultraviolet is associated with many types of solar structure, prominences and filaments, the supergranulation cells and network, active regions and their associated loop structures and other features. Simultaneous observations in lines of different characteristic temperatures provide a three-dimensional probe of the solar atmosphere. In the instrument, the principal polychromatic position observes the Lyman continuum, Lα, C II, C III, O IV, O VI, and Mg x with seven detectors simultaneously from the same spatial image element, 5″ in size. Approximately 60 additional polychromatic positions are used routinely to carry out specific observing programs, for example, covering several lines of a given stage of ionization, observing lines or continuum from specific species of interest such as helium in prominences, comparing combinations of lines from a given ionic species such as O v where the relative intensities give a rather direct measurement of the density at a given temperature, or measuring differing positions in the Lyman continuum providing intensity measurements which can be interpreted in terms of the departure from ionization equilibrium.

Images of Impurity Line Emission in the Extreme Ultraviolet Region From the Large Helical Device With an Edge Stochastic Magnetic Field Layer

2014 ◽  
Vol 42 (10) ◽  
pp. 2542-2543 ◽  
Author(s):  
Shigeru Morita ◽  
Erhui Wang ◽  
Chunfeng Dong ◽  
Tetsutarou Oishi ◽  
Motoshi Goto ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Extreme Ultraviolet ◽  
Line Emission ◽  
Ultraviolet Region ◽  
Field Layer ◽  
Stochastic Magnetic Field
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