Middle Atmosphere Temperature and Dynamics as Revealed from D-region Observations

The concept of so-called meteorological control of the ionospheric D-region is presently undergoing development. According to this concept the electron concentration in this region is governed not only by solar and geomagnetic parameters but strongly depends on the temperature and dynamical regime of the mesosphere and stratosphere. How this connection between D-region and meteorological parameters can be used to obtain some information about middle atmosphere temperature and dynamics is examined. The essential points of the meteorological control concept are reviewed and the influence of turbulence on nitric oxide distribution and thus the ion production rate is discussed

Second experiment on the investigation of ion-molecular reaction constants directly in the ionosphere

Ionospheric ion-molecular interaction

Rates of Basic Ion-molecular Processes in the Ionosphere

Literature review on basic ion-molecular reaction rates in ionospher

General overview of the solar activity effects on the lower ionosphere

Solar activity influences the ionospheric D region. That influence manifests itself both in the form of various solar induced disturbances and in the form of the D region dependence on solar activity parameters (UV-flux, interplanetary magnetic field, solar wind etc.) in quiet conditions. Relationship between solar activity and meteorological control of the D region behavior is considered in detail and examples of strong variations of aeronomical parameters due to solar or meteorological events are given

The method of determination of the long-term trends in the F2 region independent of geomagnetic activity

International audienceA detailed analysis of the f oF2 data at the Sverdlovsk station is performed to answer the question: whether the long-term trends of the F2-layer parameter detected recently are mainly due to the long-term changes in geomagnetic activity during the recent decades. Two methods to derive trends independent of geomagnetic activity are developed. It is found that both methods agree well and give a relative nongeomagnetic trend of about - 0.0015 per year (or an absolute nongeomagnetic trend of about - 0.015 MHz per year). The close relation of foF2 to Ap found by several authors is mainly due to a high correlation between the foF2 deviations from the regression line and year-to-year changes in the Ap index rather than to systematic long-term changes of Ap as has been suggested earlier

Long-term trends in the relation between daytime and nighttime values of <I>fo</I>F2

The data from the vertical ionospheric sounding for 12 stations over the world were analyzed to find the relation between the values of <I>fo</I>F2 for 02:00 LT and 14:00 LT of the same day. It is found that, in general, there exists a negative correlation between <I>fo</I>F2(02) and <I>fo</I>F2(14). The value of the correlation coefficient <I>R(fo</I>F2) can be in some cases high enough and reach minus 0.7&ndash;0.8. The value of <I>R(fo</I>F2) demonstrates a well pronounced seasonal variations, the highest negative values being observed at the equinox periods of the year. It is also found that <I>R(fo</I>F2) depends on geomagnetic activity: the magnitude of <I>R(fo</I>F2) is the highest for the choice of only magnetically quiet days (<I>A_p</I>&lt;6), decreasing with the increase of the limiting value of <I>A_p</I>. For a fixed limitation on <I>A_p</I>, the value of <I>R(fo</I>F2) depends also on solar activity. Apparently, the effects found are related to thermospheric winds. Analysis of long series of the vertical sounding data shows that there is a long-term trend in <I>R(fo</I>F2) with a statistically significant increase in the <I>R(fo</I>F2) magnitude after about 1980. Similar analysis is performed for the <I>fo</I>F2(02)/<I>fo</I>F2(14) ratio itself. The ratio also demonstrates a systematic trend after 1980. Both trends are interpreted in terms of long-term changes in thermospheric circulation

Progress in D-region studies during MAP

During MAP, active studies of the ionospheric D region were performed. The most interesting and fruitful were those in which variations of D region parameters and of the dynamical regime of the middle atmosphere were intercompared. As a result, the general picture of the D region behavior became much clearer than before. It appears that the D region is strongly influenced by dissipation of internal gravity waves which come from below and are destroyed at altitudes 80 to 100 km. This influence is much stronger in winter than in summer due to the filtering effect of the stratospheric circulation on these waves. As a result, strong day-to-day variability of the D region in winter and relative stability in summer, is now clear