Long-term Changes in Ionospheric F-layer Characteristics
Abstract
A study of ionospheric sounding data from Slough and Chilton, UK from 1935 to 2005, and from Stanley in the Falkland Islands between 1945 and 2005, revealed long-term and apparently systematic changes in the characteristics of the F1 and F2 layers. Specifically, the visibility of the critical frequency of the ionospheric F1 layer has changed with time, with the trends anti-correlated between the two hemispheres. The relative strengths of the semi-annual and annual variations in the critical frequency of the F2 layer also exhibit strong trends with similar hemispheric anti-correlation. Both effects are attributed to changes in composition driven by the variability in geomagnetic activity which controls the average latitudinal extent of the auroral ovals. The extent of the auroral ovals modulates the latitudinal extent of convection cells transporting molecular-rich air into the upper thermosphere. The anti-correlation between stations is harder to explain and may be due to the relative sensitivity of the ionosphere to changes in the position of the geomagnetic pole at each of the stations.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFMSA12A..01S
- Keywords:
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- 1650 Solar variability (7537);
- 2400 IONOSPHERE (6929);
- 2407 Auroral ionosphere (2704);
- 2419 Ion chemistry and composition (0335);
- 2427 Ionosphere/atmosphere interactions (0335)