HR: 09:22h
AN: SA51C-05 INVITED     [Abstracts]
TI: Trends in the E and F1 Regions of the Earth's Ionosphere
AU: * Bremer, J
EM: bremer@iap-kborn.de
AF: Leibniz-Institute of Atmospheric Physics, Schloss-Str. 6, Kuehlungsborn, D-18225, Germany
AB: Ground based ionosonde measurements are a very important source for investigations of long-term variations in the ionospheric E and F1 regions. Data of such observations are available at many different ionospheric stations all over the world since partly more than 50 years. Here mainly standard parameters foE, h'E, and foF1 are used for trend analyses. Two main problems have to be taken into consideration in these analyses. Firstly, the data series have to be homogeneous, i. e. the observations should not be disturbed by artificial steps due to changes in the used technical equipment or in the evaluation algorithm. Secondly, the strong solar and geomagnetic influences upon the ionospheric data have carefully to be removed by an appropriate regression analysis. Otherwise it is impossible to detect the small trends in the different ionospheric parameters. The trends derived at individual stations differ markedly. Nevertheless, the mean global trends estimated from the trends at the different stations are statistically significant different from zero (positive trends in foE and foF1, negative trend in h'E). These mean trends can at least qualitatively be explained by an increasing atmospheric greenhouse effect (increase of CO2 content or of other greenhouse gases) and decreasing ozone values. The positive foE trend is also in qualitative agreement with rocket mass spectrometer observations of ion densities in the E region. Furthermore first indications could be found that the changing ozone trend (before about 1979, between 1979 until 1995, and after about 1995) can modify the estimated long-term variations at least in foE.
DE: 1610 Atmosphere (0315, 0325)
DE: 2487 Wave propagation (0689, 3285, 4275, 4455, 6934)
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 6929 Ionospheric physics (1240, 2400)
SC: SPA-Aeronomy [SA]
MN: 2007 Joint Assembly