scholarly journals VLBI and Broad-Band Radio Spectra Study of the Strongly Variable Extragalactic Object 0524+034

2001 ◽  
Vol 205 ◽  
pp. 100-101
Author(s):  
Y.Y. Kovalev ◽  
A.G. Gorshkov ◽  
V.K. Konnikova ◽  
M.G. Mingaliev
Keyword(s):  
Broad Band ◽  
Monitoring Data ◽  
Extragalactic Object ◽  
Relativistic Jet ◽  
Rapid Changes ◽  
Jet Plasma ◽  
Band Spectra ◽  
Long Term Variations

Results of the first measurements of a VLBI structure of 0524+034 at 6 cm at the EVN+HartRAO in 1999 and recent broad-band spectra monitoring data are reported. We suppose that precession of the relativistic jet can be one of the possible mechanisms to account for the observed milliarcsecond structure and the strong long-term variations of the spectrum. The detected rapid changes may be interpreted as a propagation of a shock in the inhomogeneous jet plasma, but interstellar scintillations can not be ruled out on the basis of available data.

scholarly journals Broad-band Radio Spectra Variability of 550 AGN in 1997-2001

2002 ◽  
Vol 19 (1) ◽  
pp. 83-87 ◽  
Author(s):  
Y. Y. Kovalev ◽  
Yu A. Kovalev ◽  
N. A. Nizhelsky ◽  
A. B. Bogdantsov
Keyword(s):  
Longitudinal Magnetic Field ◽  
Broad Band ◽  
Physical Nature ◽  
Model Interpretation ◽  
Vlbi Observations ◽  
Relativistic Jet ◽  
Typical Behaviour ◽  
5 Ghz ◽  
Term Monitoring

AbstractResults are presented of long-term monitoring at the radio telescope RATAN–600 and a model interpretation of instantaneous 1–22 GHz spectra at six frequencies for a sample of 550 compact extragalactic radio sources. The sources are selected from the Preston et al. (1985) VLBI survey and are located in the declination range from −30° to +43°. Dependence of the index of variability on frequency is analysed for different subsamples. Factors of flux density variations range from 1 to 15. A typical behaviour of spectra evolution during strong radio outbursts in various objects is recognised suggesting a common physical nature of the variability. Invoking VLBI observations in spectra–structure analysis, we find that usually more than 70% of the total emission is coming from the mas scale at frequencies higher than 5 GHz. The observed variability can be explained in the model with a relativistic jet of parsec scale in the longitudinal magnetic field or in the shock-in-jet model.

Using Long-Term Population Monitoring Data to Prioritize Conservation Action among Rare Plant Species

2019 ◽  
Vol 39 (2) ◽  
pp. 169 ◽  
Author(s):  
Holly L. Bernardo ◽  
Pati Vitt ◽  
Rachel Goad ◽  
Susanne Masi ◽  
Tiffany M. Knight
Keyword(s):  
Plant Species ◽  
Population Monitoring ◽  
Monitoring Data ◽  
Rare Plant ◽  
Conservation Action ◽  
Rare Plant Species

Fluvial magnetic susceptibility as a proxy for long‐term variations of mountain permafrost development in the Alp‐Carpathian region

Boreas ◽  
2021 ◽  
Author(s):  
Zoltán Püspöki ◽  
Philip Leonard Gibbard ◽  
Annamária Nádor ◽  
Edit Thamó‐Bozsó ◽  
Pál Sümegi ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Carpathian Region ◽  
Mountain Permafrost ◽  
Long Term Variations

Long-term variations of C1–C5 alkyl nitrates and their sources in Hong Kong

2021 ◽  
Vol 270 ◽  
pp. 116285
Author(s):  
Lewei Zeng ◽  
Hai Guo ◽  
Xiaopu Lyu ◽  
Beining Zhou ◽  
Zhenhao Ling ◽  
...  
Keyword(s):  
Hong Kong ◽  
Alkyl Nitrates ◽  
Long Term Variations

Application of singular spectrum analysis in reconstruction of the annual signal from GRACE

2020 ◽  
Vol 14 (3) ◽  
pp. 295-302
Author(s):  
Chuandong Zhu ◽  
Wei Zhan ◽  
Jinzhao Liu ◽  
Ming Chen
Keyword(s):  
Time Series ◽  
Spectrum Analysis ◽  
Singular Spectrum Analysis ◽  
Mixture Effect ◽  
Singular Spectrum ◽  
Grace Data ◽  
Terrestrial Water ◽  
Annual Signal ◽  
Long Term Variations

AbstractThe mixture effect of the long-term variations is a main challenge in single channel singular spectrum analysis (SSA) for the reconstruction of the annual signal from GRACE data. In this paper, a nonlinear long-term variations deduction method is used to improve the accuracy of annual signal reconstructed from GRACE data using SSA. Our method can identify and eliminate the nonlinear long-term variations of the equivalent water height time series recovered from GRACE. Therefore the mixture effect of the long-term variations can be avoided in the annual modes of SSA. For the global terrestrial water recovered from GRACE, the peak to peak value of the annual signal is between 1.4 cm and 126.9 cm, with an average of 11.7 cm. After the long-term and the annual term have been deducted, the standard deviation of residual time series is between 0.9 cm and 9.9 cm, with an average of 2.1 cm. Compared with the traditional least squares fitting method, our method can reflect the dynamic change of the annual signal in global terrestrial water, more accurately with an uncertainty of between 0.3 cm and 2.9 cm.

scholarly journals Long term variations measurement of electromagnetic field exposures in Alcalá de Henares (Spain)

2017 ◽  
Vol 598 ◽  
pp. 657-668 ◽  
Author(s):  
R. Sánchez-Montero ◽  
C. Alén-Cordero ◽  
P.L. López-Espí ◽  
J.M. Rigelsford ◽  
F. Aguilera-Benavente ◽  
...  
Keyword(s):  
Electromagnetic Field ◽  
Long Term Variations
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