The relation between the F region trough and the polar cap convection is investigated using satellite tomography observations and the convection model by citet{PapRic02}. The poleward and equatorward edges of the trough are determined from the satellite data and their locations are plotted in magnetic coordinates together with the convection pattern. The study is limited to equinox seasons. The field of view of the tomography measurements is 56{degs}--72{degs}

Results of correlation studies between solar proxies and clouds suggest that there is a solar effect on the ccurrence of clouds. However, there is a possibility that terrestrial quasi-periodic and sporadic phenomena, such as ENSO and/or major volcanic eruptions, which have an effect on the cloud formation, may influence the results of statistical studies of the Sun–cloud relation. We show that removing ENSO and volcanic years from the full-set

Studies of the relation between cosmic rays (CR) (solar activity) and atmospheric cloudiness are mostly based on the satellite ISCCP cloud data. However, doubts have been cast that these relations can be an artifact of instrumental effects, i.e., of the masking/obscuring low clouds by higher clouds in the satellite view. If this is the case, most of the earlier results based on ISCCP data would be devaluated. Here, we reanalyze the ISCCP cloud coverage

There is evidence that solar activity variations can affect the cloud cover at Earth. However, it is still unclear hich solar driver plays the most important role in the cloud formation. Here we use partial correlations to distinguish between the effects of two solar drivers (cosmic rays and the UV irradiance) and the mutual relations between clouds at different altitudes. We find that the solar influence on cloud cover is not uniquely defined by

This paper is the second in a series on a study of the link between IMF and sporadic-E layers within the polar cap. In Paper I (Voiculescu et al., 2006), an analysis of the sporadic-E data from Thule and Longyearbyen was presented. Here we concentrate on the electric field mechanism of sporadic-E generation. By means of model calculations we show that the mechanism is effective even at Thule, where the direction of the geomagnetic field departs from

In this paper we investigate the relationship between polar cap sporadic-E layers and the direction of the interplanetary magnetic field (IMF) using a 2-year database from Longyearbyen (75.2 CGM Lat, Svalbard) and Thule (85.4 CGM Lat, Greenland). It is found that the MLT distributions of sporadic-E occurrence are different at the two stations, but both are related to the IMF orientation. This relationship, however, changes from the centre of the