A multi-diagnostic spectral analysis of penumbral microjets

Context. Penumbral microjets (PMJs) are short-lived, jet-like objects found in the penumbra of sunspots. They were first discovered in chromospheric lines and have later also been shown to exhibit signals in transition region (TR) lines. Their origin and manner of evolution is not yet settled. Aims. We perform a comprehensive analysis of PMJs through the use of spectral diagnostics that span from photospheric to TR temperatures to constrain PMJ properties. Methods We employed high-spatial-resolution Swedish 1-m Solar Telescope observations in the Ca II 8542 Å and H α lines, IRIS slit-jaw images, and IRIS spectral observations in the Mg II h & k lines, the Mg II 2798.75 Å & 2798.82 Å triplet blend, the C II 1334 Å & 1335 Å lines, and the Si IV 1394 Å & 1403 Å lines. We derived a wide range of spectral diagnostics from these and investigated other secondary phenomena associated with PMJs. Results. We find that PMJs exhibit varying degrees of signal in all of our studied spectral lines. We find low or negligible Doppler velocities and velocity gradients throughout our diagnostics and all layers of the solar atmosphere associated with these. Dark features in the inner wings of H α and Ca II 8542 Å imply that PMJs form along pre-existing fibril structures. We find evidence for upper photospheric heating in a subset of PMJs through emission in the wings of the Mg II triplet lines. There is little evidence for ubiquitous twisting motion in PMJs. There is no marked difference in onset-times for PMJ brightenings in different spectral lines. Conclusions. PMJs most likely exhibit only very modest mass-motions, contrary to earlier suggestions. We posit that PMJs form at upper photospheric or chromospheric heights at pre-existing fibril structures.

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Observations of the Quiet Sun with 6″ Resolution

Symposium - International Astronomical Union ◽

10.1017/s0074180900036627 ◽

1980 ◽

Vol 86 ◽

pp. 53-55

Author(s):

M. R. Kundu ◽

A. P. Rao ◽

F. T. Erskine ◽

J. D. Bregman

Keyword(s):

High Resolution ◽

Radio Emission ◽

Transition Region ◽

Spatial Resolution ◽

Radio Telescope ◽

Solar Radio ◽

High Spatial Resolution ◽

Solar Radio Emission ◽

Quiet Sun ◽

Millimeter Wavelengths

Solar radio emission at centimeter and millimeter wavelengths originates in the chromosphere and transition region and is a useful probe for the temperature and density in these regions. High spatial resolution observations of the quiet sun provide valuable information on the structure of the solar atmosphere. We have performed high resolution (~ 6″ (E-W) x 15″ (N-S)) observations at 6 cm with the Westerbork Synthesis Radio Telescope (WSRT) in June 1976 in order to search for the radio analog of the supergranulation network and to study the extent and symmetry of limb brightening. The use of the WSRT for high spatial resolution solar mapping has been described by Bregman and Felli (1976), Kundu et al. (1977), and others.

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WHY IS NON-THERMAL LINE BROADENING OF SPECTRAL LINES IN THE LOWER TRANSITION REGION OF THE SUN INDEPENDENT OF SPATIAL RESOLUTION?

The Astrophysical Journal ◽

10.1088/2041-8205/799/1/l12 ◽

2015 ◽

Vol 799 (1) ◽

pp. L12 ◽

Cited By ~ 38

Author(s):

B. De Pontieu ◽

S. McIntosh ◽

J. Martinez-Sykora ◽

H. Peter ◽

T. M. D. Pereira

Keyword(s):

Transition Region ◽

Spatial Resolution ◽

Spectral Lines ◽

The Sun ◽

Line Broadening ◽

Lower Transition ◽

Thermal Line

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Spectral interferences and their correction in atomic emission spectral analysis

Industrial laboratory Diagnostics of materials ◽

10.26896/1028-6861-2019-85-1-ii-15-32 ◽

2019 ◽

Vol 85 (1II)) ◽

pp. 15-32

Author(s):

A. A. Pupyshev

Keyword(s):

Spectral Analysis ◽

Microwave Plasma ◽

Atomic Emission ◽

Spectral Lines ◽

Emission Spectral Analysis ◽

Electric Discharges ◽

Analytical Line ◽

Spectral Interferences ◽

Atomic Emission Spectral Analysis ◽

Wide Range

The main sources of spectral interferences in atomic emission spectral analysis (AESA) are considered, including both wide-range (bremsstrahlung and recombination continuum, radiation of hot condensed particles and electrode ends, scattered light in the spectrometer, overlapping of the analytical line by the wings of the neighbor strong spectral lines of interfering elements, imposition of the components of molecular bands with the very close lines) and narrow-band (partial or complete overlapping of the analytical line with atomic or ionic lines of the sample elements, electrodes and discharge atmosphere; superposition of spectra from higher orders of reflection in conventional diffraction spectrometers and from neighboring orders in two-dimensional echelle spectrometers). The features of their manifestation in various sources of spectrum excitation (flames, DC arc, spark discharges, arc plasma discharges, inductively coupled plasma, microwave plasma, low-pressure electric discharges, laser spark) are considered. The possibilities of reducing the level of spectral interferences or elimination of the spectral noise at the stage of design and manufacturing of AESA devices, as well as upon selecting and adjusting of operation conditions of the analysis are shown. Much attention is paid to the most easily implemented in practice off-peak correction of wide-range spectral interferences. The modern methods of background correction under the spectral peak (under-peak) using a software for atomic emission spectrometers and providing creation of various mathematical models of the background signal in the vicinity of the analytical line at the stage of developing a specific AESA technique are considered. The issues of the choice of spectral lines for analytical measurements, tables and atlases of spectral lines, electronic databases used for this purpose are considered in detail. Specific features of application of the method of inter-element correction with direct spectral overlapping of the lines are given. The operating sequence for taking into account spectral interferences when developing the analysis techniques is proposed.

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Rapid Variations in Intergranular Space

International Astronomical Union Colloquium ◽

10.1017/s0252921100029122 ◽

1993 ◽

Vol 141 ◽

pp. 222-224 ◽

Cited By ~ 1

Author(s):

A. Nesis ◽

A. Hanslmeier ◽

R. Hammer ◽

R. Komm ◽

W. Mattig ◽

...

Keyword(s):

Line Width ◽

Spatial Resolution ◽

High Spatial Resolution ◽

Doppler Velocity ◽

Continuum Intensity ◽

Velocity Gradients ◽

The Continuum ◽

Intergranular Space

AbstractSpectrograms of high spatial resolution taken every 15s reveal rapid variations of the continuum intensity and line width. Variations of the latter seem to be related to Doppler velocity gradients.

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A superior cathodoluminescence spectral analysis and imaging system for semiconductor characterisation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100088506 ◽

1991 ◽

Vol 49 ◽

pp. 838-839

Author(s):

P J Wright

Keyword(s):

Spectral Analysis ◽

Electron Microscope ◽

Spatial Resolution ◽

High Spatial Resolution ◽

Imaging System ◽

Fibre Optic ◽

Transmission Losses ◽

The Past ◽

Improved Performance ◽

Electron Microscopes

Cathodoluminescence is a useful technique in the structural and electro optical characterisation of semiconductors. When performed in a electron microscope, both high spatial resolution images and spectra may be obtained by use of the correct equipment.Many designs for instruments suitable for cathodoluminescence spectral analysis and imaging in electron microscopes have been described in the literature during the past 25 years. These have often exhibited improved performance when compared with commercially available systems. The prime reason for this has been the willingness of the dedicated CL researcher to mount large, heavy monochromators directly to the chamber of their microscope. The result has been a microscope committed to CL analysis. However, many potential CL users have to use shared facilities and may not compromise the performance or appearance of the microscope. Subsequently, many CL systems have had the monochromator decoupled from the CL collection optics by either fibre optic bundles or quartz fibres. This has allowed the monochromator and its associated detectors to be easily decoupled from the SEM when not in use. Considerable transmission losses have been incurred and in many cases, it has been necessary to duplicate detectors to allow both spectral analysis and imaging. This has resulted in instruments which were less than optimum in both efficiency and operation.

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Volcanic Hot-Spot detection using SENTINEL-2: results from the comparison with MODIS-MIROVA thermal signals.

10.5194/egusphere-egu2020-5095 ◽

2020 ◽

Author(s):

Francesco Massimetti ◽

Diego Coppola ◽

Marco Laiolo ◽

Sébastien Valade ◽

Corrado Cigolini ◽

...

Keyword(s):

Spatial Resolution ◽

High Spatial Resolution ◽

Hot Spot ◽

Detection Algorithm ◽

Distinct Pattern ◽

Pixel Resolution ◽

Spot Detection ◽

Wide Range ◽

Volcanic Processes ◽

Sentinel 2

<p>In the satellite thermal remote sensing, the high-spatial resolution sensors may improve thermal constraining of volcanic phenomena, with direct implications on the comprehension of volcanic processes and monitoring purposes. Here we present a new hot-spot detection algorithm, developed for SENTINEL 2 (S2) data, which combines contextual spectral and spatial analysis, applied on the 8a-11-12 SWIR bands with 20 meters/pixel resolution. The algorithm is able to detect and count the number of hotspot-contaminated pixels (S2Pix), in a wide range of environments and for several types of volcanic activities. The S2-derived thermal trends, retrieved at different worldwide key-cases volcanoes, are than compared with the Volcanic Radiative Power (VRP) from MODIS images processed by the MIROVA system during the period 2016-2019. Dataseries showed an overall excellent correlation between the two imagery suites, enhancing the higher sensitivity of SENTINEL-2 to detect small size and subtle, low-temperature thermal signals. Results outline a relation between the S2Pix and VRP ratios and the volcanic processes (i.e. lava flows, domes, lakes, open-vent activity) producing a distinct pattern in terms of size and intensity of the thermal anomaly. Moreover, the high-spatial resolution of S2 imagery potentiality let to decrypt which is the thermal contribution of the different active volcanic portions, and to understand their evolution in terms of intensity and persistence. Our analysis indicates how the combination of high- (S2) and moderate- (MODIS) resolution thermal timeseries represent an improvement in the space-based volcano monitoring that can be useful for monitoring applications and communities which relate with active volcanoes.</p>

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Frequency Spectrum-Based Optimal Texture Window Size Selection for High Spatial Resolution Remote Sensing Image Analysis

Journal of Spectroscopy ◽

10.1155/2019/4970376 ◽

2019 ◽

Vol 2019 ◽

pp. 1-15

Author(s):

Min Cao ◽

Dongping Ming ◽

Lu Xu ◽

Ju Fang ◽

Lin Liu ◽

...

Keyword(s):

Remote Sensing ◽

Spectral Analysis ◽

Spatial Resolution ◽

High Spatial Resolution ◽

Texture Feature ◽

Window Size ◽

Remote Sensing Image ◽

Selection Method ◽

Image Texture ◽

Scale Selection

Image texture is an important visual cue in image processing and analysis. Texture feature expression is an important task of geo-objects expression by using a high spatial resolution remote sensing image. Texture features based on gray level co-occurrence matrix (GLCM) are widely used in image spatial analysis where the spatial scale is especially of great significance. Based on the Fourier frequency-spectral analysis, this paper proposes an optimal scale selection method for GLCM. Different subset textures are firstly upscaled by GLCM with different window sizes. Then the multiscale texture feature images are converted into the frequency domain by Fourier transform. Consequently, the radial distribution and angular distribution curves changing with different window sizes from spectrum energy can be achieved, by which the texture window size can be selected. In order to verify the validity of this proposed texture scale selection method, this paper uses high-resolution fusion images to classify land cover based on multiscale texture expression. The results show that the proposed method combining frequency-spectral analysis-based texture scale selection can guarantee the quality and accuracy of the classification, which further proves the effectiveness of optimal texture window size selection method bases on frequency spectrum analysis. Other than scale selection in spatial domain, this paper casts a novel idea for texture scale selection in the frequency domain, which is meant for scale processing of remote sensing image.

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Scientific Programmes with India's National Large Solar Telescope and their contribution to Prominence Research

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313011198 ◽

2013 ◽

Vol 8 (S300) ◽

pp. 355-361

Author(s):

S. S. Hasan

Keyword(s):

High Resolution ◽

Adaptive Optics ◽

High Spatial Resolution ◽

Optical Design ◽

Primary Objective ◽

Spectral Lines ◽

Solar Telescope ◽

Optical Elements ◽

Scientific Questions ◽

Adaptive Optics System

AbstractThe primary objective of the 2-m National Large Solar Telescope (NLST) is to study the solar atmosphere with high spatial and spectral resolution. With an innovative optical design, NLST is an on-axis Gregorian telescope with a low number of optical elements and a high throughput. In addition, it is equipped with a high order adaptive optics system to produce close to diffraction limited performance.NLST will address a large number of scientific questions with a focus on high resolution observations. With NLST, high spatial resolution observations of prominences will be possible in multiple spectral lines. Studies of magnetic fields, filament eruptions as a whole, and the dynamics of filaments on fine scales using high resolution observations will be some of the major areas of focus.

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