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Trends in the F 2 layer parameters at the end of the 1990s and the beginning of the 2000s
Author(s) -
Danilov A. D.,
Konstantinova A. V.
Publication year - 2013
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/jgrd.50501
Subject(s) - depth sounding , ionosphere , environmental science , standard deviation , meteorology , magnitude (astronomy) , atmospheric sciences , statistics , geodesy , mathematics , physics , geography , astrophysics , cartography , astronomy
The behavior of the critical frequency foF 2 of the ionospheric F 2 layer is considered for the period 1990–2010. Various available databanks of ionospheric vertical sounding data are described and compared. The analysis is performed in terms of comparison of the foF 2 data for the period 1958–1980 to the data for 1990–2010. Two moments of the day (14:00 LT and the after‐sunset moment) and two seasons (winter and summer) are considered for 12 stations for which the necessary data were available. The scatter of the foF 2 values (in terms of the standard deviation, SD) relative to the dependence on the solar activity index F 10.7 is considered. It is demonstrated that the values of SD for the period 1998–2010 are much higher than for the period 1958–1979. This increase in the SD includes two factors: real increase in the foF 2 scatter and systematic decrease (negative trend) in foF 2 . This systematic decrease makes it possible to provide an independent evaluation of the trend in foF 2 : −0.03 MHz per year. Analysis of foF 2 behavior for each of all 12 stations is performed. The obtained linear trends are negative for all stations, but the trend magnitude varies from one station to another. The trends for two moments of time are found of the same order of magnitude: −0.024 and −0.054 MHz per year for the summer and winter seasons, respectively. Some conclusions on the behavior of the hmF 2 trends for the same period are presented. Possible causes of the changes in the trends in the F 2 layer parameters are discussed.