scholarly journals Phase Spectra Seen from Space

1998 ◽  
Vol 185 ◽  
pp. 455-456
Author(s):  
Th. Straus ◽  
F.-L. Deubner ◽  
B. Fleck ◽  
C. Marmolino ◽  
G. Severino ◽  
...  
Keyword(s):  
Time Series ◽  
Line Intensity ◽  
Solar Rotation ◽  
Disk Center ◽  
Mean Velocity ◽  
Continuum Intensity ◽  
Doppler Imager ◽  
Low Pass ◽  
Line Depth ◽  
The Continuum

A 15 hour time series of simultaneous spectroscopic measurements of the continuum intensity, Doppler shift, and line depth in the Ni I 6768Å line at disk center of the quiet sun has been obtained during a guest investigator campaign with the Michelson Doppler Imager (MDI, see Scherrer et al. 1995). In addition, the line intensity has been calculated from the continuum intensity and the line depth data. The spatial shifts due to solar rotation have been approximately removed during the observation run by shifting the CCD read-out area by 1 pixel every 4 minutes. Small residual shifts have been removed during the data analysis. Before applying the Fourier analysis, a (temporal) low pass filtered mean velocity (line of sight component of solar rotation) and mean intensity (center-limb variation) has been removed from each frame. Finally, the continuum intensity (C), line intensity (I), and velocity (V) time series have been subjected to a 3D Fourier transform, yielding κ - ω power, cross power, phase difference, and coherence spectra. The data can now be compared to recent ground-based observations (Deubner, 1990; Deubner et al., 1992; Straus & Bonaccini, 1997).

scholarly journals Average Variations of Photospheric FeI and FeII Line Parameters as Function of the Magnetic Filling Factor

1990 ◽  
Vol 138 ◽  
pp. 41-46
Author(s):  
P.N. Brandt ◽  
M. Steinegger
Keyword(s):  
Filling Factor ◽  
Line Strength ◽  
Blue Shift ◽  
Disk Center ◽  
Flux Tubes ◽  
On Line ◽  
Fourier Transform Spectra ◽  
Similar Depth ◽  
Line Depth ◽  
The Continuum

A series of 17 Fourier transform spectra taken at the McMath telescope near disk center in regions of different magnetic field strengths were analyzed. Applying a multi-variate regression analysis magnetic filling factors 0 < α ≥ 0.11 were determined. With α increasing from 0 to 0.11, line bisectors averaged over groups of lines of similar depth are found to show a blue shift decreasing from 0.35 km s–1 to nearly 0.1 km s–1, when referred to the MgI line λ5172.7å. The bisectors of FeII lines exhibit smaller blue shifts than FeI lines. The increase of bisector red shift near the continuum with increasing α, found earlier by Brandt and Solanki (1987), was confirmed and is tentatively interpreted as a manifestation of downdrafts in the vicinity of flux tubes (Deinzer et al., 1984).A significant increase of line width (typically between 3 and 8%, depending on line strength) and a decrease of line depth is found with increasing filling factor. For strong lines the equivalent width W shows no variation or a slight increase, while for the weaker lines a reduction of W between a few % and > 10% is found.

EELS white line intensities calculated for the 3d and 4d metals

1989 ◽  
Vol 47 ◽  
pp. 388-389
Author(s):  
C. C. Ahn ◽  
D. H. Pearson ◽  
P. Rez ◽  
B. Fultz
Keyword(s):  
Experimental Data ◽  
Line Intensity ◽  
Transition Probabilities ◽  
Initial Increase ◽  
White Line ◽  
Hartree Fock ◽  
Line Intensities ◽  
Integrated Intensity ◽  
X Ray Absorption ◽  
The Continuum

Previous experimental measurements of the total white line intensities from L2,3 energy loss spectra of 3d transition metals reported a linear dependence of the white line intensity on 3d occupancy. These results are inconsistent, however, with behavior inferred from relativistic one electron Dirac-Fock calculations, which show an initial increase followed by a decrease of total white line intensity across the 3d series. This inconsistency with experimental data is especially puzzling in light of work by Thole, et al., which successfully calculates x-ray absorption spectra of the lanthanide M4,5 white lines by employing a less rigorous Hartree-Fock calculation with relativistic corrections based on the work of Cowan. When restricted to transitions allowed by dipole selection rules, the calculated spectra of the lanthanide M4,5 white lines show a decreasing intensity as a function of Z that was consistent with the available experimental data.Here we report the results of Dirac-Fock calculations of the L2,3 white lines of the 3d and 4d elements, and compare the results to the experimental work of Pearson et al. In a previous study, similar calculations helped to account for the non-statistical behavior of L3/L2 ratios of the 3d metals. We assumed that all metals had a single 4s electron. Because these calculations provide absolute transition probabilities, to compare the calculated white line intensities to the experimental data, we normalized the calculated intensities to the intensity of the continuum above the L3 edges. The continuum intensity was obtained by Hartree-Slater calculations, and the normalization factor for the white line intensities was the integrated intensity in an energy window of fixed width and position above the L3 edge of each element.

scholarly journals Low-Pass Filtering Method for Poisson Data Time Series

2021 ◽  
Vol 11 (10) ◽  
pp. 4524
Author(s):  
Victor Getmanov ◽  
Vladislav Chinkin ◽  
Roman Sidorov ◽  
Alexei Gvishiani ◽  
Mikhail Dobrovolsky ◽  
...  
Keyword(s):  
Time Series ◽  
Finite Impulse Response ◽  
Digital Processing ◽  
Distributed Data ◽  
Gaussian Filter ◽  
Experimental Physics ◽  
Filtering Method ◽  
Filter Synthesis ◽  
Low Pass ◽  
Poisson Data

Problems of digital processing of Poisson-distributed data time series from various counters of radiation particles, photons, slow neutrons etc. are relevant for experimental physics and measuring technology. A low-pass filtering method for normalized Poisson-distributed data time series is proposed. A digital quasi-Gaussian filter is designed, with a finite impulse response and non-negative weights. The quasi-Gaussian filter synthesis is implemented using the technology of stochastic global minimization and modification of the annealing simulation algorithm. The results of testing the filtering method and the quasi-Gaussian filter on model and experimental normalized Poisson data from the URAGAN muon hodoscope, that have confirmed their effectiveness, are presented.

scholarly journals The continuum intensity as a function of magnetic field

2011 ◽  
Vol 531 ◽  
pp. A112 ◽  
Author(s):  
P. Kobel ◽  
S. K. Solanki ◽  
J. M. Borrero
Keyword(s):  
Magnetic Field ◽  
Continuum Intensity ◽  
The Continuum

scholarly journals VISUAL ANALYSIS OF RECURRENCE OF TIME SERIES OF THE COORDINATES ENU IN THE GPS STATIONS

2018 ◽  
Vol 24 (4) ◽  
pp. 470-484
Author(s):  
Alfonso Tierra ◽  
Rubén León ◽  
Alexis Tinoco-S ◽  
Carolina Cañizares ◽  
Marco Amores ◽  
...  
Keyword(s):  
Time Series ◽  
Continuous Monitoring ◽  
Visual Analysis ◽  
Finite Impulse Response ◽  
Satellite System ◽  
Nearest Neighbours ◽  
Low Pass ◽  
Global Navigation Satellite ◽  
Low Pass Filters ◽  
Content Information

Abstract The time series content information about the dynamic behavior of the system under study. This behavior could be complex, irregular and no lineal. For this reason, it is necessary to study new models that can solve this dynamic more satisfactorily. In this work a visual analysis of recurrence from time series of the coordinate’s variation ENU (East, North, Up) will be made. This analysis was obtained from nine continuous monitoring stations GPS (Global Navigation Satellite System); the intention is to study their behavior, they belong to the Equatorian GPS Network that materializes the reference system SIRGAS - ECUADOR. The presence of noise in the observations was reduced using digital low pass filters with Finite Impulse Response (FIR). For these series, the time delay was determined using the average mutual information, and for the minimum embedding dimension the False Nearest Neighbours (FNN) method was used; the purpose is to obtain the recurrent maps of each coordinates. The results of visual analysis show a strong tendency, especially in the East and North coordinates, while the Up coordinates indicate discontinued, symmetric and periodic behavior.

scholarly journals Investigations of Broad Line Region Structure and Kinematics Using Variability

1989 ◽  
Vol 134 ◽  
pp. 93-95
Author(s):  
C. Martin Gaskell ◽  
Anuradha P. Koratkar ◽  
Linda S. Sparke
Keyword(s):  
Time Series ◽  
Cross Correlation ◽  
Sampling Interval ◽  
Broad Line ◽  
Line Flux ◽  
Line Region ◽  
Cross Correlations ◽  
The Mean ◽  
The Cross ◽  
The Continuum

Gaskell and Sparke (1986) showed that one can determine the sizes of BLRs more accurately that the mean sampling interval by cross-correlating the continuum flux time series with a line flux time series. The position of the peak in the cross-correlation function (CCF) and its shape give an indication of the BLR size. The technique is explained in detail in Gaskell and Peterson (1987). The widely propagated misunderstanding is that the method involves simply interpolating both time series and cross-correlating them (in which case the CCF is dominated by the cross-correlations of “made-up” data). Actually the method involves cross correlating the observed points in one time series (continuum, say) with the linear interpolations of the other series (line flux). The line flux time series must always be smoother than the continuum time series it is derived from. We have usually employed the method with the interpolation done both ways round and averaged them (to reduce errors due to the interpolation) and we can intercompare the two results (to investigate errors).

Spectral analysis of palaeomagnetic time series and the geomagnetic spectrum

1982 ◽  
Vol 306 (1492) ◽  
pp. 203-209 ◽  
Keyword(s):  
Time Series ◽  
Spectral Analysis ◽  
Spectral Density ◽  
Density Function ◽  
Power Density ◽  
Spectral Density Function ◽  
Power Spectral Density Function ◽  
Power Spectral ◽  
Polarity Reversals ◽  
The Continuum

There are now sufficient archaeomagnetic data from rapidly deposited sediments and baked clays to start bridging the gap in the geomagnetic spectrum between the frequency ranges covered by observatory records and polarity reversals. The form of the continuum spectrum of internal origin can be only loosely constrained but is broadly consistent with earlier speculations. The power spectral density function appears to increase rapidly with period up to periods of about 60 years, then more slowly up to a plateau in the region of 10 4 to 10 5 years, and thereafter starts to fall. There is somewhat inconclusive evidence for a drop in power density at periods around 10 2 years. Prospects for refining the spectrum are excellent.

Lunar and solar magnetic variations at Abinger: their detection and estimation by spectral anaylsis via Fourier transforms

1970 ◽  
Vol 268 (1187) ◽  
pp. 233-263 ◽  
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Fourier Transforms ◽  
Solar Rotation ◽  
Amplitude Spectrum ◽  
Discrete Fourier Transforms ◽  
Detection And Estimation ◽  
High Resolution Analysis ◽  
High Resolution Power ◽  
Resolution Analysis

The geomagnetic field measured at any point on Earth as a function of time shows periodic variations due to atmospheric processes. A method of time series analysis based on discrete Fourier transforms is developed for the detection and estimation of lines in the frequency spectrum; the method gives estimates, with error limits, of the amplitudes of sinusoidal variations in the data, and these estimates are unbiased by noise. The method is used to determine the lunar and solar variations present in Abinger declination records, data for a period of 17 years (1927—56) being used. The coherence between Abinger data and time series that model the lunar and solar input functions to the atmosphere aids the identification of lines in the Abinger spectrum. The amplitude spectrum of magnetic declination at Abinger shows prominent solar peaks at 1, 2, 3, 4 cycles per day (c/d), and lunar peaks at 0.0703, 1.932, and 2.932 c/d. Sidebands of the solar diurnal peak at 1 ± 0.037 c/d are attributed to a solar rotation mechanism, and this is supported by a high resolution power spectrum that shows the width of these sidebands. The high resolution analysis also shows annual and semi-annual splitting of the solar diurnal and semi-diurnal lines, and of the lunar semi-diurnal line.

scholarly journals Radial Differential Rotation of Solar Corona using Radio Emissions

2021 ◽  
Author(s):  
Vivek Kumar Singh ◽  
Satish Chandra ◽  
Sanish Thomas ◽  
Som Kumar Sharma ◽  
Hari Om Vats
Keyword(s):  
Time Series ◽  
Solar Corona ◽  
Solar Rotation ◽  
Rotation Period ◽  
Solar Radio Emission ◽  
Correlation Technique ◽  
Emission Data ◽  
Height Range ◽  
Data Gaps ◽  
Frequency Radiation

Abstract The present work is an effort to investigate possible radial variations in the solar coronal rotation by analyzing the solar radio emission data at 15 different frequencies (275-1755 MHz) for the period starting from July 1994 to May 1999. We used a time series of disk-integrated radio flux recorded daily at these frequencies through radio telescopes situated at Astronomical Observatory of the Jagellonian University in Cracow. The different frequency radiation originates from different heights in the solar corona. Existing models, indicate its origin at the height range from nearly ∼12, 000 km (for emission at 275 MHz), below up to ∼2, 400 km (for emission at 1755 MHz). There are some data gaps in the time series used for the study, so we used statistical analysis using the Lomb-Scargle Periodogram (LSP). This method has successfully estimated the periodicity present in time series even with such data gaps. The rotation period estimated through LSP shows variation in rotation period, which is compared with the earlier reported estimate using auto correlation technique. The present study indicates some similarity as well as contradiction with studies reported earlier. The radial and temporal variation in solar rotation period are presented and discussed for the whole period analyzed.

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