Intensity Enhancement of O Vi Ultraviolet Emission Lines in Solar Spectra Due to Opacity

Keenan, F. P.; Doyle, J. G.; Madjarska, M. S.; Rose, S. J.; Bowler, L. A.; Britton, Julie A.; McCrink, Lisa; Mathioudakis, M.

doi:10.1088/2041-8205/784/2/l39

Cited by 8 publications

(5 citation statements)

References 20 publications

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“…Values such as this has been observed before, for example with Skylab data by , where values have been found which are 1.5 at 2 ′′ above the solar limb. More recent work by Keenan et al (2014) has shown for the first time that in the solar case, that this ratio can change in both directions as the result of opacity.…”

Section: Characterising a Single Blobmentioning

confidence: 93%

The Impact of a Filament Eruption on Nearby High-Lying Cool Loops

Harra¹,

Matthews²,

Long³

et al. 2014

ApJ

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The first spectroscopic observations of cool Mg II loops above the solar limb observed by NASA's Interface Region Imaging Spectrograph (IRIS;De Pontieu et al. (2014)) are presented. During the observation period IRIS is pointed off-limb allowing the observation of high-lying loops, which reach over 70 Mm in height. Low-lying cool loops were observed by the IRIS slit jaw camera for the entire 4 hour observing window. There is no evidence of a central reversal in the line profiles and the Mg II h/k ratio is approximately 2. The Mg II spectral lines show evidence of complex dynamics in the loops with Doppler velocities reaching ± 40 km/s. The complex motions seen indicate the presence of multiple threads in the loops and separate blobs. Towards the end of the observing period, a filament eruption occurs that forms the core of a coronal mass ejection. As the filament erupts, it impacts these high-lying loops, temporarily impeding these complex flows, most likely due to compression. This causes the plasma motions in the loops become blue-shifted and then red-shifted. The plasma motions are seen before the loops themselves start to oscillate as they reach equilibrium following the impact. The ratio of the Mg h/k lines also increases following the impact of the filament.

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Section: Characterising a Single Blobmentioning

confidence: 93%

The Impact of a Filament Eruption on Nearby High-Lying Cool Loops

Harra¹,

Matthews²,

Long³

et al. 2014

ApJ

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“…Therefore, the need arises of accounting for the angular dependence of the spectral distribution which plays directly into experimental design considerations and spectral analysis. This effect has previously been observed in astrophysical and laboratory plasmas 22,23 , and several methods have been proposed to diagnose the geometry of astrophysical bodies by studying it 18,24 .…”

Section: Introductionmentioning

confidence: 65%

A novel method to measure ion density in ICF experiments using x-ray spectroscopy of cylindrical tracers

et al. 2020

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The indirect drive approach to inertial confinement fusion (ICF) has undergone important advances in the past years. The improvements in temperature and density diagnostic methods are leading to more accurate measurements of the plasma conditions inside the hohlraum and therefore to more efficient experimental designs. The implementation of dot spectroscopy has proven to be a versatile approach to extracting spaceand time-dependent electron temperatures. In this method a microdot of a mid-Z material is placed inside the hohlraum and its K-shell emission spectrum is used to determine the plasma temperature. However, radiation transport of optically thick lines acting within the cylindrical dot geometry influences the outgoing spectral distribution in a manner that depends on the viewing angle. This angular dependence has recently been studied in the high energy density (HED) regime at the OMEGA laser facility, which allowed us to design and benchmark appropriate radiative transfer models that can replicate these geometric effects. By combining these models with the measurements from the dot spectroscopy experiments at the National Ignition Facility (NIF), we demonstrate here a novel technique that exploits the transport effects to obtain time-resolved measurements of the ion density of the tracer dots, without the need for additional diagnostics. We find excellent agreement between experiment and simulation, opening the possibility of using these geometric effects as a density diagnostic in future experiments.

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“…Therefore, for non-spherical plasmas, the enhancement of optically thick lines depends on the position of the observer with respect to the plasma. This effect has been observed in astrophysical plasmas [45] and has applications to charaterizing the geometry of astrophysical bodies from their line ratios [42,46]. However, to our knowledge, it has never been used for density measurements in laboratory plasmas (although a potential experiment to observe these effects was proposed by Mancini et al [47]).…”

Section: Introductionmentioning

confidence: 93%

The use of geometric effects in diagnosing ion density in ICF-related dot spectroscopy experiments

Pérez-Callejo

Liedahl

Schneider

et al. 2019

High Energy Density Physics

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We describe a method to calculate the ion density of High Energy Density (HED) cylindrical plasmas used in Dot Spectroscopy experiments. This method requires only spectroscopic measurements of the Heα region obtained from two views (Face-on and Side-on). We make use of the fact that the geometry of the plasma affects the observed flux of optically thick lines. The ion density can be derived from the aspect ratio (height-to-radius) of the cylinder and the optical depth of the Heα-y line (1s2p 3 P 1 → 1s 2 1 S 0 ). The aspect ratio and the optical depth of the y line are obtained from the spectra using ratios measured from the two directions of emission of the optically thick Heα-w line (1s2p 1 P 1 → 1s 2 1 S 0 ) and the ratio of the optically thick to thin lines. The method can be applied to mid-Z elements at ion densities of 10 19 − 10 20 cm −3 and temperatures of a the order of keV, which is a relevant regime for Inertial Confinement Fusion (ICF) experiments.

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Intensity Enhancement of O Vi Ultraviolet Emission Lines in Solar Spectra Due to Opacity

Cited by 8 publications

References 20 publications

The Impact of a Filament Eruption on Nearby High-Lying Cool Loops

The Impact of a Filament Eruption on Nearby High-Lying Cool Loops

A novel method to measure ion density in ICF experiments using x-ray spectroscopy of cylindrical tracers

The use of geometric effects in diagnosing ion density in ICF-related dot spectroscopy experiments

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