Statistics of long-term ionospheric measurements

[摘要] It is shown that after elimination of the dominant influence ofsolar activity, the height hmF2 of the maximum ionisation of the ionosphere(which is inversely linearly related to M(3000)F2 as described for example bythe Shimazaki formula) shows a marked decrease during the recent solarminimum (2005 to 2009) of about 20 km. This is in accordance with results ofstudies of the decreased neutral density of the lower thermosphere and thedensity decrease at about 400 km during the unusual recent solar minimum. Itis also shown that there is a trend reversal in the height of the ionospherehmF2 in about 1963/1964 with a negative trend from 1942 to 1963 and apositive trend from 1964 to 2005. This is in contrast to the results reportedin most other publications of ionospheric long-term trends. There is nosignificant trend in foF2 and, particularly, none of the effects describedabove for hmF2 could be found in foF2.

[学科分类] 电子、光学、磁材料