Long-term variation of the semi-annual wave maxima in geomagnetic activity

1989 ◽  
Vol 33 (4) ◽  
pp. 379-390 ◽  
Author(s):  
Emil M. Apostolov ◽  
Vojtěch Letfus ◽  
J. Pýcha
Keyword(s):  
Geomagnetic Activity ◽  
Term Variation

scholarly journals Ionospheric F1 layer long-term trends and the geomagnetic control concept

2008 ◽  
Vol 26 (12) ◽  
pp. 3793-3803 ◽  
Author(s):  
A. V. Mikhailov
Keyword(s):  
Geomagnetic Activity ◽  
Temperature Changes ◽  
Term Variation ◽  
Control Concept ◽  
E Region ◽  
Long Term Trends ◽  
Long Term Trend ◽  
The Magnetic Field ◽  
Long Term Variations

Abstract. A previous approach to the ionospheric long-term trend analysis has been applied to the foF1 observations from Slough and Rome in order to investigate a possible relationship between the foF1 and the long-term variation of geomagnetic activity. A 40-year period, starting in 1962, has been used for the analysis. According to the results obtained earlier for F2 and E-region trends, geomagnetic control of the long-term variation has also been revealed for the foF1. Thus, it is now possible to speak about the geomagnetic control of the ionospheric trends in the whole ionosphere. This is not surprising as the Earth's ionosphere is a single entity that is strongly controlled, either directly or indirectly, by the magnetic field. As with the F2-region, this geomagnetic control is provided via neutral composition and temperature changes. A very long-term (centennial) increase in geomagnetic activity in the 20th century is seen in the long-term foF1 variations as well. After its removal, the residual foF1 trends are very small and insignificant. In principal, this means that the observed foF1 long-term variations have a natural origin and can be attributed to solar and geomagnetic activity long-term variations. However, the situation in the thermosphere has been changing since 1997 and available foF2 observations at the two stations reveal information about the "break down" of the geomagnetic control in the F2-region. Possible reasons of these changes are discussed.

Is the long-term variation of the estimated GPS differential code biases associated with ionospheric variability?

GPS Solutions ◽  
2015 ◽  
Vol 20 (3) ◽  
pp. 313-319 ◽  
Author(s):  
Jiahao Zhong ◽  
Jiuhou Lei ◽  
Xiankang Dou ◽  
Xinan Yue
Keyword(s):  
Ionospheric Variability ◽  
Differential Code Biases ◽  
Term Variation
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