Universal time variations of the auroral hemispheric power and their interhemispheric asymmetry from TIMED/GUVI observations

2016 ◽  
Vol 121 (10) ◽  
pp. 10,258-10,268 ◽  
Author(s):  
Xiaoli Luan ◽  
Wenbin Wang ◽  
Alan Burns ◽  
Xiankang Dou
Keyword(s):  
Universal Time ◽  
Interhemispheric Asymmetry ◽  
Time Variations

scholarly journals Universal Time Variations in Space Weather

2020 ◽  
Author(s):  
Michael Lockwood ◽  
Mathew J Owens ◽  
Carl Haines ◽  
Luke Barnard ◽  
Christopher John Scott ◽  
...  
Keyword(s):  
Space Weather ◽  
Universal Time ◽  
Time Variations

Influence of AAM and OAM on the Universal Time Variations

2008 ◽  
Author(s):  
Yavor Chapanov ◽  
Daniel Gambis ◽  
Vasile Mioc ◽  
Cristiana Dumitrache ◽  
Nedelia A. Popescu
Keyword(s):  
Universal Time ◽  
Time Variations

scholarly journals Earth Orientation Parameters 1899.7-1992.0 In The Hipparcos Reference Frame

1998 ◽  
Vol 11 (1) ◽  
pp. 553-553
Author(s):  
J. Vondrák ◽  
C. Ron ◽  
I. Pešek ◽  
A. Čepek
Keyword(s):  
Polar Motion ◽  
Universal Time ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
The Earth ◽  
Hipparcos Catalogue ◽  
Time Variations ◽  
Celestial Reference System ◽  
Orientation Parameters ◽  
Made In

The optical astrometry observations of latitude/universal time variations made with 48 instruments at 31 observatories are used to determine the Earth orientation parameters (EOP) since the beginning of the century. The Hipparcos Catalogue is used to bring more than four million individual observations, made in the interval 1899.7-1992.0, into the International Celestial Reference System. The Earth orientation parameters (polar motion, celestial pole offsets and, since 1956.0, also universal time UT1) are determined at 5-day intervals, with average uncertainties ranging from 8 mas (in the eighties) to about 40 mas (in the forties). Making use of very long series of ground-based observations, the solution also leads to the improvement of proper motions of about ten per cent of the observed Hipparcos stars, with precision of ±0.2 — 0.5 mas/yr. In addition, 474 auxiliary parameters, describing the rheological properties of the Earth and seasonal deviations of the observations at contributing observatories, are found. The new solution provides the EOP series suitable for further analyses, e.g., for studying long-periodic polar motion, length-of-day changes or precession/nutation.

scholarly journals Astrometric star catalogues as combination of Hipparcos/Tycho catalogues with ground-based observations

2004 ◽  
pp. 1-8 ◽  
Author(s):  
J. Vondrák
Keyword(s):  
Universal Time ◽  
Optical Observations ◽  
Proper Motions ◽  
Earth Orientation ◽  
Optical Wavelength ◽  
Primary Representation ◽  
Hipparcos Catalogue ◽  
Time Variations ◽  
Celestial Reference System ◽  
Better Than

The successful ESA mission Hipparcos provided very precise parallaxes positions and proper motions of many stars in optical wavelength. Therefore it is a primary representation of International Celestial Reference System in this wavelength. However, the shortness of the mission (less than four years) causes some problems with proper motions of the stars that are double or multiple. Therefore, a combination of the positions measured by Hipparcos satellite with ground-based observations with much longer history provides a better reference frame that is more stable in time. Several examples of such combinations are presented (ACT, TYCHO-2, FK6, GC+HIP, TYC2+HIP, ARIHIP) and briefly described. The stress is put on the most recent Earth Orientation Catalogue (EOC) that uses about 4.4 million optical observations of latitude/universal time variations (made during the twentieth century at 33 observatories in Earth orientation programmes), in combination with some of the above mentioned combined catalogues. The second version of the new catalogue EOC-2 contains 4418 objects, and the precision of their proper motions is far better than that of Hipparcos Catalogue.

scholarly journals Universal Time Variations in the ap and Dst Indices and Their Possible Cause.

1993 ◽  
Vol 45 (7) ◽  
pp. 563-572 ◽  
Author(s):  
S. Saroso ◽  
T. Iyemori ◽  
M. Sugiura
Keyword(s):  
Universal Time ◽  
Time Variations ◽  
Possible Cause

Short-term prediction of universal time variations dUT1

2019 ◽  
Author(s):  
Sergej Krylov ◽  
Vadim Perepelkin ◽  
Alexandra Filippova
Keyword(s):  
Universal Time ◽  
Short Term ◽  
Term Prediction ◽  
Time Variations ◽  
Short Term Prediction
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