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Worldwide variation in atmospheric noise intensities with sunspot number: An in‐depth look at the 20–24 hour seasonal time block
Author(s) -
Joglekar P. J.,
Sathiamurthy T. S.
Publication year - 1975
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/rs010i006p00601
Subject(s) - sunspot , noise (video) , block (permutation group theory) , ionosphere , sunspot number , environmental science , range (aeronautics) , variation (astronomy) , standard deviation , atmospheric noise , meteorology , mathematics , statistics , atmospheric sciences , physics , solar cycle , infrasound , astrophysics , computer science , acoustics , geometry , materials science , composite material , quantum mechanics , astronomy , artificial intelligence , magnetic field , solar wind , image (mathematics)
Comparisons of the variation of atmospheric radio noise intensities for 20–24 hr to sunspot numbers have been completed. Statistical dependence between the noise intensities and sunspot numbers was found for different seasons at a number of frequencies for many locations in the global network of ARN‐2 noise recorders. The noise intensities generally tended to decrease with sunspot number in the range from 50 kHz to 5 MHz, which is presumed to be due to increases in residual ionospheric absorption during nighttime. At frequencies greater than 5 MHz, noise intensities increased with sunspot number in many cases, which would be expected from our present knowledge of ionospheric behavior in the HF range. By convention, CCIR treats year‐to‐year variation in the noise intensities as random and includes them in the prediction uncertainty σ F am (for which one value is given at a frequency for a seasonal time block for all locations) in system performance evaluation. An error analysis on a global basis shows that a large portion of the year‐to‐year variability is due to sunspot variation. This suggests the possibility of improved noise estimates.