Long-term trends of <i>f</i>oE and geomagnetic activity variations
A relationship between <i>f</i>oE trends and geomagnetic activity long-term variations has been revealed for the first time. By analogy with earlier obtained results on the <i>f</i>oF2 trends it is possible to speak about the geomagnetic control of the <i>f</i&...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2003-03-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/21/751/2003/angeo-21-751-2003.pdf |
| Summary: | A relationship between <i>f</i>oE
trends and geomagnetic activity long-term variations has been revealed for the
first time. By analogy with earlier obtained results on the <i>f</i>oF2 trends
it is possible to speak about the geomagnetic control of the <i>f</i>oE
long-term trends as well. Periods of increasing geomagnetic activity correspond
to negative <i>f</i>oE trends, while these trends are positive for the
decreasing phase of geomagnetic activity. This "natural" relationship
breaks down around 1970 (on some stations later) when pronounced positive <i>f</i>oE
trends have appeared on most of the stations considered. The dependence of <i>f</i>oE
trends on geomagnetic activity can be related with nitric oxide variations at
the E-layer heights. The positive <i>f</i>oE trends that appeared after the
"break down" effect may also be explained by the [NO] decrease which
is not related to geomagnetic activity variations. But negative trends or
irregular <i>f</i>oE variations on some stations for the same time period
require some different mechanism. Chemical pollution of the lower thermosphere
due to the anthropogenic activity may be responsible for such abnormal <i>f</i>oE
behavior after the end of the 1960s.<br><br><b>Key words. </b>Ionosphere
(ionosphere-atmosphere interactions; ionospheric disturbances) |
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| ISSN: | 0992-7689 1432-0576 |