Trends in the ionospheric E and F regions over Europe

Abstract

Abstract. Continuous observations in the ionospheric E and F regions have been regularly carried out since the ®fties of this century at many ionosonde stations. Using these data from 31 European stations long-term trends have been derived for dierent parameters of the ionospheric E layer (h¢ E, foE), F1 layer (foF1) and F2 layer (hmF2, foF2). The detected trends in the E and F1 layers (lowering of the E region height h¢E; increase of the peak electron densities of the E and F1 layers, foE and foF1) are in qualitative agreement with model predictions of an increasing atmospheric greenhouse eect. In the F2 region, however, the results are more complex. Whereas in the European region west of 30°E negative trends in hmF2 (peak height of the F2 layer) and in the peak electron density (foF2) have been found, in the eastern part of Europe (east of 30°E) positive trends dominate in both parameters. These marked longitudinal dierences cannot be explained by an increasing greenhouse eect only, here probably dynamical eects in the F2 layer seem to play an essential role.

Trends in the solar quiet geomagnetic field variation linked to the Earth's magnetic field secular variation and increasing concentrations of greenhouse gases

“…Rishbeth and Roble [1992] also predicted an increase in the peak electron density in the E layer, corresponding to an increase in f o E of 0.05-0.08 MHz. This theoretical prediction, and the experimental results obtained by Bremer [1998Bremer [ , 2004Bremer [ , 2008, Danilov [2002], and Mikhailov [2006], of a positive trend in f o E made us suspect that Sq should also present a positive trend.…”

“…On the other hand, the increase in greenhouse gas concentrations, expected to produce an increase in the peak value of the electron concentration in the E region ( f o E) [Rishbeth and Roble, 1992;Bremer, 1998Bremer, , 2004Bremer, , 2008, should also be expected to induce some effect on Sq.…”

Geomagnetic control of the <i>fo</i>F2 long-term trends

“…However an analysis has shown that the worldwide pattern of the F2 and E-layer parameter long-term trends is very complicated and cannot be explained suciently by this eect. Further analysis by Bremer (1998) of many European ionosonde stations and by Upadhyay and Mahajan (1998) of a global set of ionosonde stations has shown that the F2-layer parameter trends turn out to be dierent both in sign and magnitude for dierent stations and this cannot be reconciled with the greenhouse hypothesis. A contradiction with this hypothesis was revealed also by Leshchenko (1996, 1998) when analyzing the foE long-term trends.…”

“…Long-term variations (trends) of the upper atmosphere and ionosphere parameters are widely discussed in recent publications due to the problem of global climate changes (see reviews by Danilov, 1997Danilov, , 1998Leshchenko, 1994, 1995;Ulich and Turunen, 1997;Rishbeth, 1997;Mikhailov, 1998, 1999;Bremer, 1992Bremer, , 1998Upadhyay and Mahajan, 1998). After the model calculations of Rishbeth (1990) and Rishbeth and Roble (1992) predicting the ionospheric eects of atmospheric greenhouse gas concentration increase, the researchers have been trying to relate the observed long-term trends in the ionospheric parameters to this greenhouse eect (Bremer, 1992;Givishvili and Leshchenko, 1994;Ulich andTurunen, 1997, Jarvis et al, 1998;Upadhyay and Mahajan, 1998).…”

The importance of geomagnetic field changes versus rising CO2levels for long-term change in the upper atmosphere

“…There are also inconsistencies between the reported magnitudes of long-term trends in ion temperature and neutral density, which still need to be reconciled (Akmaev 2012). In addition, several ionosonde stations show increases in the height of the peak of the F 2 layer, h m F 2 , rather than the expected decrease (Bremer 1998;Upadhyay & Mahajan 1998), and many stations show significant trends in the critical frequency of the F 2 layer, f o F 2 (Upadhyay & Mahajan 1998;Elias & Ortiz de Adler 2006), which is directly related to the maximum electron density of the F 2 layer, N m F 2 (N m F 2 / (f o F 2 ) 2 ). These discrepancies with the predicted effects of enhanced CO 2 levels mean that other drivers of long-term change may be important also.…”