scholarly journals Doppler shift oscillations of a sunspot detected by CYRA and IRIS

2020 ◽  
Vol 642 ◽  
pp. A231
Author(s):  
D. Li ◽  
X. Yang ◽  
X. Y. Bai ◽  
J. T. Su ◽  
Z. J. Ning ◽  
...  
Keyword(s):  
Line Profile ◽  
Gaussian Function ◽  
Correlation Method ◽  
Doppler Velocity ◽  
Temperature Minimum ◽  
Sunspot Umbra ◽  
Spatially Resolved ◽  
Doppler Shifts ◽  
Time Distance ◽  
The Moment

Context. The carbon monoxide (CO) molecular line at around 46655 Å in solar infrared spectra is often used to investigate the dynamic behavior of the cold heart of the solar atmosphere, i.e., sunspot oscillation, especially at the sunspot umbra. Aims. We investigated sunspot oscillation at Doppler velocities of the CO 7-6 R67 and 3-2 R14 lines that were measured by the Cryogenic Infrared Spectrograph (CYRA), as well as the line profile of Mg II k line that was detected by the Interface Region Imaging Spectrograph (IRIS). Methods. A single Gaussian function is applied to each CO line profile to extract the line shift, while the moment analysis method is used for the Mg II k line. Then the sunspot oscillation can be found in the time–distance image of Doppler velocities, and the quasi-periodicity at the sunspot umbra are determined from the wavelet power spectrum. Finally, the cross-correlation method is used to analyze the phase relation between different atmospheric levels. Results. At the sunspot umbra, a periodicity of roughly 5 min is detected at the Doppler velocity range of the CO 7-6 R67 line that formed in the photosphere, while a periodicity of around 3 min is discovered at the Doppler velocities of CO 3-2 R14 and Mg II k lines that formed in the upper photosphere or the temperature minimum region and the chromosphere. A time delay of about 2 min is measured between the strong CO 3-2 R14 line and the Mg II k line. Conclusions. Based on the spectroscopic observations from the CYRA and IRIS, the 3 min sunspot oscillation can be spatially resolved in the Doppler shifts. It may come from the upper photosphere or the temperature minimum region and then propagate to the chromosphere, which might be regarded as a propagating slow magnetoacoustic wave.

Searching Ultimate Nanometrology for AlOx Thickness in Magnetic Tunnel Junction by Analytical Electron Microscopy and X-ray Reflectometry

2005 ◽  
Vol 11 (5) ◽  
pp. 431-445 ◽  
Author(s):  
Se Ahn Song ◽  
Tatsumi Hirano ◽  
Jong Bong Park ◽  
Kazutoshi Kaji ◽  
Ki Hong Kim ◽  
...  
Keyword(s):  
Line Profile ◽  
Analytical Electron Microscopy ◽  
Random Access ◽  
Chemical Properties ◽  
Magnetic Tunnel Junction ◽  
Chromatic Aberration ◽  
Time Resolved ◽  
X Ray ◽  
Spatially Resolved ◽  
Beam Damage

Practical analyses of the structures of ultrathin multilayers in tunneling magneto resistance (TMR) and Magnetic Random Access Memory (MRAM) devices have been a challenging task because layers are very thin, just 1–2 nm thick. Particularly, the thinness (∼1 nm) and chemical properties of the AlOx barrier layer are critical to its magnetic tunneling property. We focused on evaluating the current TEM analytical methods by measuring the thickness and composition of an AlOx layer using several TEM instruments, that is, a round robin test, and cross-checked the thickness results with an X-ray reflectometry (XRR) method. The thickness measured by using HRTEM, HAADF-STEM, and zero-loss images was 1.1 nm, which agreed with the results from the XRR method. On the other hand, TEM-EELS measurements showed 1.8 nm for an oxygen 2D-EELS image and 3.0 nm for an oxygen spatially resolved EELS image, whereas the STEM-EDS line profile showed 2.5 nm in thickness. However, after improving the TEM-EELS measurements by acquiring time-resolved images, the measured thickness of the AlOx layer was improved from 1.8 nm to 1.4 nm for the oxygen 2D-EELS image and from 3.0 nm to 2.0 nm for the spatially resolved EELS image, respectively. Also the observed thickness from the EDS line profile was improved to 1.4 nm after more careful optimization of the experimental parameters. We found that EELS and EDS of one-dimensional line scans or two-dimensional elemental mapping gave a larger AlOx thickness even though much care was taken. The reasons for larger measured values can be found from several factors such as sample drift, beam damage, probe size, beam delocalization, and multiple scattering for the EDS images, and chromatic aberration, diffraction limit due to the aperture, delocalization, alignment between layered direction in samples, and energy dispersion direction in the EELS instrument for EELS images. In the case of STEM-EDS mapping with focused nanoprobes, it is always necessary to reduce beam damage and sample drift while trying to maintain the signal-to-noise (S/N) ratio as high as possible. Also we confirmed that the time-resolved TEM-EELS acquisition technique improves S/N ratios of elemental maps without blurring the images.

scholarly journals Stellar Populations and Kinematics in Seyfert Galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 71-75 ◽  
Author(s):  
N. V. Asari ◽  
L. R. Vega ◽  
A. Garcia-Rissmann ◽  
R. M. González Delgado ◽  
T. Storchi-Bergmann ◽  
...  
Keyword(s):  
Equivalent Width ◽  
Correlation Method ◽  
Seyfert Galaxies ◽  
Population Synthesis ◽  
Stellar Kinematics ◽  
Spatially Resolved ◽  
Fitting Method ◽  
Stellar Velocity ◽  
Velocity Dispersions ◽  
Nuclear Signal

AbstractOur aim is to study the stellar kinematics in hosts of AGN. We do so by measuring nuclear stellar velocity dispersions (σ⋆). Our sample comprises spectra of 78 objects, 69 of which are Seyfert galaxies, in the region around the λλ8498.02, 8542.09, 8662.14 Calcium triplet (CaT). We investigate two methods to measure σ⋆: (1) the direct fitting method (DFM), which makes use of our stellar population synthesis code Starlight, and (2) the cross-correlation method (CCM), for which we use the fxcor package in IRAF. Both methods yield velocity dispersions consistent to within 19 km/s on-average. We have also measured the CaT equivalent width (WCaT) and the λ3933 CaII K equivalent width (WK) for the objects in our sample. Other studies have shown that WK is a powerful tracer of starbursts in Seyfert nuclei, so we check if WCaT can be used in the same way. We have also analysed a sub-sample of 34 spatially resolved objects with reasonably good off-nuclear signal-to-noise. We study the spatial variations of both σ⋆ and WCaT. We see no dilution in WCaT for composite starburst + Seyfert 2 galaxies, in contrast to the dilution in the WK (studied by other authors) for the same objects.

scholarly journals High-precision measurement of velocity profiles in laser-created chlorine plasma

1995 ◽  
Vol 13 (4) ◽  
pp. 503-510 ◽  
Author(s):  
O. Renner ◽  
E. Krouský ◽  
T. Mißalla ◽  
E. Förster ◽  
G. Hölzer
Keyword(s):  
Spectral Lines ◽  
Plasma Parameters ◽  
High Precision Measurement ◽  
One Dimensional ◽  
Electron Temperature Gradient ◽  
Spatially Resolved ◽  
Doppler Shifts ◽  
Velocity Gradients ◽  
Marquardt Algorithm ◽  
The One

A vertical dispersion variant of the Johann spectrometer has been used to record the highresolution X-ray spectra of the chlorine He-like resonance line group emitted from lowradiance plasma. The emission profiles were measured at two observation angles and decomposed into single spectral lines by using a fit based on the Levenberg-Marquardt algorithm. The results of computerized analysis of the one-dimensional (1-D) spatially resolved spectra were used to evaluate the distribution of the main plasma parameters. The electron temperature gradient 7.5·104 eV cm-1 was computed by modeling the measured spectra with the collisional-radiative package RATION. The blowoff maximum velocities 4.2–6.1·107 cm s-1 and the velocity gradients 0.9–1.6·109 s-1 were determined from the Doppler shifts of individual spectral lines within their different spatial extent.

scholarly journals Solar 5-min Oscillation Amplitude Anisotropy and Doppler Velocity Systematics

1988 ◽  
Vol 123 ◽  
pp. 63-65
Author(s):  
J.R. Kuhn ◽  
C.M. O'Neill ◽  
L.B. Gilliam
Keyword(s):  
Spatial Resolution ◽  
Oscillation Amplitude ◽  
Level Line ◽  
Line Center ◽  
Doppler Velocity ◽  
Systematic Effect ◽  
Conflicting Information ◽  
Doppler Shifts ◽  
Line Asymmetry ◽  
Observing Techniques

Several measurements of 5-min velocity amplitudes have yielded confusing and conflicting information on the l and m dependence of the modal excitation (Kuhn and O'hanlon, 1983 – henceforth KO; Deubner, 1985; and Hill et al. 1985). We have obtained considerably more data than was described in KO using similar observing techniques. Additional analysis has illuminated a systematic effect related to the finite spatial resolution, and line asymmetry of the data that can lead to errors in inferred velocity amplitudes. Even though Doppler shifts are calculated from the Fraunhofer line center positions the effect can lead to 5-min oscillation amplitude errors at the 10 percent or greater level. Line wing observations should be more susceptible, and comparable resolution 2-dimensional data may be less sensitive to this systematic.

scholarly journals Spectroscopic detection of coronal plasma flows in loops undergoing thermal non-equilibrium cycles

2020 ◽  
Vol 634 ◽  
pp. A54 ◽  
Author(s):  
Gabriel Pelouze ◽  
Frédéric Auchère ◽  
Karine Bocchialini ◽  
Clara Froment ◽  
Susanna Parenti ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Line Of Sight ◽  
Doppler Velocity ◽  
Temperature Plasma ◽  
Imaging Spectrometer ◽  
Periodic Flows ◽  
Evaporation And Condensation ◽  
Spatially Resolved ◽  
Euv Imaging ◽  
Non Equilibrium

Context. Long-period intensity pulsations were recently detected in the EUV emission of coronal loops and attributed to cycles of plasma evaporation and condensation driven by thermal non-equilibrium (TNE). Numerical simulations that reproduce this phenomenon also predict the formation of periodic flows of plasma at coronal temperatures along some of the pulsating loops. Aims. We aim to detect these predicted flows of coronal-temperature plasma in pulsating loops. Methods. We used time series of spatially resolved spectra from the EUV imaging spectrometer (EIS) onboard Hinode and tracked the evolution of the Doppler velocity in loops in which intensity pulsations have previously been detected in images of SDO/AIA. Results. We measured signatures of flows that are compatible with the simulations but only for a fraction of the observed events. We demonstrate that this low detection rate can be explained by line of sight ambiguities combined with instrumental limitations, such as low signal-to-noise ratio or insufficient cadence.

scholarly journals Measurement of Slice Thickness of a Medical Image using a Wedge Phantom

2020 ◽  
Vol 9 (4) ◽  
pp. 327-329
Keyword(s):  
Line Profile ◽  
Imaging System ◽  
Medical Images ◽  
Wedge Angle ◽  
Gaussian Function ◽  
Thickness Measurement ◽  
Slice Thickness ◽  
Line Profiles ◽  
Slice Profile ◽  
Digital Phantom

Slice thickness measurement is an essential parameter of performance evaluation for the medical imaging system. This study demonstrates the characteristics of slice thickness measurement for medical images using a wedge digital phantom. A wedge-shaped digital phantom was generated and the ideal edge response function (ERF) was extracted from line profile in single slice. The corresponding slice profile was calculated by the derivative of ERF. The wedge phantom obtained by applying gaussian convolving to a digital phantom was also generated to produce similarities to real medical images. Unlike an ideal slice profile, it was estimated by the full width half maximum (FWHM) of the Gaussian function fitting. In addition, we evaluate the effect of background noise and wedge angle for the wedge phantom. The estimated FWHM of the image with noise added was increased by 10.4% compared to the image without noise. However, the FWHM from the line profiles averaging on the noise-added image was estimated by 0.2% reduction than the noise-free image. The line profiles averaging improves the accurate measurement of slice thickness by decreasing the noise. Despite the wedge angle changing from 45 to 30 degrees, the resulting FWHM was estimated to have less than 1% difference. However, the length of the line profile to be acquired should be increased as the wedge angle increases.

scholarly journals A Spatiotemporal Study and Location-Specific Trip Pattern Categorization of Shared E-Scooter Usage

2021 ◽  
Vol 13 (22) ◽  
pp. 12527
Author(s):  
Maximilian Heumann ◽  
Tobias Kraschewski ◽  
Tim Brauner ◽  
Lukas Tilch ◽  
Michael H. Breitner
Keyword(s):  
Clustering Algorithm ◽  
City Center ◽  
Time Saving ◽  
Work Related ◽  
Spatially Resolved ◽  
Point Of Interest ◽  
Density Based Clustering ◽  
Time Distance ◽  
The City ◽  
Average Cluster

This study analyzes the temporally resolved location and trip data of shared e-scooters over nine months in Berlin from one of Europe’s most widespread operators. We apply time, distance, and energy consumption filters on approximately 1.25 million trips for outlier detection and trip categorization. Using temporally and spatially resolved trip pattern analyses, we investigate how the built environment and land use affect e-scooter trips. Further, we apply a density-based clustering algorithm to examine point of interest-specific patterns in trip generation. Our results suggest that e-scooter usage has point of interest related characteristics. Temporal peaks in e-scooter usage differ by point of interest category and indicate work-related trips at public transport stations. We prove these characteristic patterns with the statistical metric of cosine similarity. Considering average cluster velocities, we observe limited time-saving potential of e-scooter trips in congested areas near the city center.

scholarly journals Complexed navigation system based on a strapdown inertial navigation system and correlation meter speed and drift

2015 ◽  
pp. 74-81
Author(s):  
Yu. A. Ivanov
Keyword(s):  
Correlation Functions ◽  
Navigation System ◽  
Inertial Navigation System ◽  
Moving Average ◽  
Inertial Navigation ◽  
Correlation Method ◽  
Strapdown Inertial Navigation System ◽  
Doppler Velocity ◽  
Speed Up ◽  
Strapdown Inertial Navigation

Integration of data and correlation meter speed strapdown inertial navigation system built by analogy with the Doppler velocity and drift, results in strong disturbances in the control loop movement of the aircraft in the horizontal plane. A method of aggregation, which takes into account the correlation method for measuring the speed, is the need to calculate the long periods of correlation functions of signals received by antennas spaced. This corrected the error strapdown inertial navigation system to speed up, speed and coordinates, eliminating the need for a moving average of the correlation functions and information retrieval speed navigation in every cycle.

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