Soft X-ray Images of the Solar Corona with a Normal-Incidence Cassegrain Multilayer Telescope

Walker, Arthur B. C.; Lindblom, Joakim F.; Barbee, Troy W.; Hoover, Richard B.

doi:10.1126/science.241.4874.1781

Cited by 137 publications

(31 citation statements)

References 34 publications

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“…Furthermore, FAL placed the chromosphere at D8000 K in their models, and signiÐcant heat Ñuxes (due to ambipolar di †usion) are present in their models down to chromospheric temperatures. At the base of their LTR A with a Cassegrain multilayer telescope by Walker et al (1988). This Ðgure shows the di †usion emission on the disk that appears to have structures on the same scale as the supergranulation.…”

Section: Discussionmentioning

confidence: 94%

Observation and Modeling of the Solar Transition Region. II. Identification of New Classes of Solutions of Coronal Loop Models

Oluseyi

Walker

Santiago

et al. 1999

ApJ

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In the present work we undertake a study of the quasi-static loop model and the observational consequences of the various solutions found. We obtain the most general solutions consistent with certain initial conditions. Great care is exercised in choosing these conditions to be physically plausible (motivated by observations). We show that the assumptions of previous quasi-static loop models, such as the models of Rosner, Tucker, & Vaiana (RTV) and Veseckey, Antiochos, & Underwood, (VAU) are not necessarily valid for small loops at transition region temperatures. We Ðnd three general classes of solutions for the quasi-static loop model, which we denote radiation-dominated loops, conduction-dominated loops, and classical loops. These solutions are then compared with observations. Departures from the classical scaling law of RTV are found for the solutions obtained. It is shown that loops of the type that we model here can make a signiÐcant contribution to lower transition regions emission via thermal conduction from the upper transition region.

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Section: Discussionmentioning

confidence: 94%

Observation and Modeling of the Solar Transition Region. II. Identification of New Classes of Solutions of Coronal Loop Models

Oluseyi

Walker

Santiago

et al. 1999

ApJ

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“…The 25-80 nm wavelength region is of particular relevance to many rapidly growing technological and scientific fields, such as solar physics [1,2] synchrotron and free electron laser facilities [3] and other EUV sources such as table-top capillary discharge lasers [4]. Some applications of EUV sources emitting in the 25-80 nm wavelength range include plasma physics [5], the characterization of materials and optical elements [6,7] materials damage [3], photochemistry of biological molecules [8], nanopatterning [9], and ultrafast single-shot microscopy [10].…”

Section: Introductionmentioning

confidence: 99%

Triple-wavelength, narrowband Mg/SiC multilayers with corrosion barriers and high peak reflectance in the 25-80 nm wavelength region

Fernández-Perea¹,

Soufli²,

Robinson³

et al. 2012

Opt. Express

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Abstract:We have developed new, Mg/SiC multilayer coatings with corrosion barriers which can be used to efficiently and simultaneously reflect extreme ultraviolet (EUV) radiation in single or multiple narrow bands centered at wavelengths in the spectral region from 25 to 80 nm. Corrosion mitigation was attempted through the use of Al-Mg or Al thin layers. Three different multilayer design concepts were developed and deposited by magnetron sputtering and the reflectance was measured at near-normal incidence in a broad spectral range. Standard Mg/SiC multilayers were also deposited and measured for comparison. They were shown to efficiently reflect radiation at a wavelength of 76.9 nm with a peak reflectance of 40.6% at near-normal incidence, the highest experimental reflectance reported at this wavelength for a narrowband coating. The demonstration of multilayer coatings with corrosion resistance and multiple-wavelength EUV performance is of great interest in the development of mirrors for space-borne solar physics telescopes and other applications requiring long-lasting coatings with narrowband response in multiple emission lines across the EUV range.

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“…The postprocessing yielded the lowest-noise image sequence to date of the outer corona between 6 and 14 R e from the Sun; the noise floor is roughly 50× lower than in the single frames from the COR2 synoptic sequence. The images reveal that the highly structured corona seen with extreme ultraviolet (EUV) images at the base of the corona (e.g., Walker et al 1988;Lemen et al 2011) extends to much larger heights in STEREO/COR2 on temporal and spatial scales down to the optical and/or sampling limit of the COR2 instrument.…”

Section: Introductionmentioning

confidence: 99%

The Highly Structured Outer Solar Corona

DeForest

Howard

Velli

et al. 2018

ApJ

133

111

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We report on the observation of fine-scale structure in the outer corona at solar maximum, using deep-exposure campaign data from the Solar Terrestrial Relations Observatory-A (STEREO-A)/COR2 coronagraph coupled with postprocessing to further reduce noise and thereby improve effective spatial resolution. The processed images reveal radial structure with high density contrast at all observable scales down to the optical limit of the instrument, giving the corona a "woodgrain" appearance. Inferred density varies by an order of magnitude on spatial scales of 50 Mm and follows an f −1 spatial spectrum. The variations belie the notion of a smooth outer corona. They are inconsistent with a well-defined "Alfvén surface," indicating instead a more nuanced "Alfvén zone"-a broad trans-Alfvénic region rather than a simple boundary. Intermittent compact structures are also present at all observable scales, forming a size spectrum with the familiar "Sheeley blobs" at the large-scale end. We use these structures to track overall flow and acceleration, finding that it is highly inhomogeneous and accelerates gradually out to the limit of the COR2 field of view. Lagged autocorrelation of the corona has an enigmatic dip around 10 R e , perhaps pointing to new phenomena near this altitude. These results point toward a highly complex outer corona with far more structure and local dynamics than has been apparent. We discuss the impact of these results on solar and solar-wind physics and what future studies and measurements are necessary to build upon them.

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Soft X-ray Images of the Solar Corona with a Normal-Incidence Cassegrain Multilayer Telescope

Cited by 137 publications

References 34 publications

Observation and Modeling of the Solar Transition Region. II. Identification of New Classes of Solutions of Coronal Loop Models

Observation and Modeling of the Solar Transition Region. II. Identification of New Classes of Solutions of Coronal Loop Models

Triple-wavelength, narrowband Mg/SiC multilayers with corrosion barriers and high peak reflectance in the 25-80 nm wavelength region

The Highly Structured Outer Solar Corona

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