Abstract. From satellite data sampling the top ionosphere in the Northern Hemisphere we have identified strong eastward ion drifts, with speeds larger than 1 km/s, widths of 1 • -2 • , occurring at similar temporal and spatial locations as rapid westward ion drifts known as sub-auroral ion drifts (SAID). We have called these events "abnormal sub-auroral ion drifts" (ASAID). Two events observed in the 20:00-22:00 MLT interval are discussed: the first occurring on 21 September 2003 and the other on 12 October 2003. Tomographic reconstructions of the electron density in the Fregion, based on satellite data, provided by the Scandinavian tomography chain, were also available. We have observed that ASAID are accompanied by upward flows with a speed of the same order as that of the zonal ion drift. They coincide with deep, narrow troughs in the total ion density, both at the altitude of the F15 DMSP satellite (850 km) and in the F-region of the ionosphere, but do not seem to be a feature of the convective transport. During the entire duration of ASAID the electron temperature is very high while, contrary to SAID, the ion temperature has no clear variation. Both events described in this paper end up turning into classical SAID. Satellite data indicate that the generator of ASAID could be located inside the plasmasphere close to the plasmapause and we suggest a possible mechanism for their formation.

[1] There is evidence that solar activity variations can affect the cloud cover at Earth. However, it is still unclear which 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 one solar driver, but both seem to play a role depending on the climatic conditions and altitude. In particular, low clouds are mostly affected by UV irradiance over oceans and dry continental areas and by cosmic rays over some mid-high latitude oceanic areas and moist lands with high aerosol concentration. High clouds respond more strongly to cosmic ray variations, especially over oceans and moist continental areas. These results provide observational constraints on related climate models.

[1] A new method utilizing stochastic inversion in determining the electric field and neutral wind from monostatic beam swing incoherent scatter measurements is described. The method consists of two stages. In the first stage, beam-aligned ion velocities from a chosen F region height interval and a set of subsequent beam directions are taken as measurements. The unknowns are the two electric field components and the field-aligned ion velocity profile. The solution gives the most probable values of the unknowns with error estimates. In the second stage, the measurements consist of beam-aligned ion velocities from the E region, and the electric fields given by the first inversion problem are also used as measurements. The number of applied beam directions may be greater than in the first inversion problem. This is a feasible approach since the neutral wind usually changes more slowly than the electric field. The solution of the second inversion problem gives the most probable values of the three neutral wind components. Results of the method are shown for 11 September 2005, when the European Incoherent Scatter (EISCAT) UHF radar was running in the CP2 experiment mode, which is a four-position 6 min monostatic cycle. In addition, from each beam direction a tristatic measurement at one F region range gate was made using two additional receivers. That allowed comparison between the monostatic and tristatic electric field results, which were in excellent agreement. The calculated neutral wind components were in good accordance with previous measurements during disturbed conditions from the same site.Citation: Nygrén, T., A. T. Aikio, R. Kuula, and M. Voiculescu (2011), Electric fields and neutral winds from monostatic incoherent scatter measurements by means of stochastic inversion,

Abstract. Recent findings suggested the possibility that planetary waves play a role in the occurrence of midlatitude sporadic E layers. To account for this, we propose here a new mechanism for large-scale accumulation of metallic ions in the midlatitude E region ionosphere driven by planetary waves in the lower thermosphere. In this process, the plasma is forced to converge horizontally and accumulate inside areas of positive vorticity set up by cyclonic neutral wind shears within a planetary wave. In its simplest form, the proposed model is similar to the well-known vertical wind shear mechanism of Es formation, but with the geometry "turned on its side." Because of the long times required for ambipolar diffusion, the new mechanism can lead to significant plasma accumulation, acting as complementary to the vertical wind shear process so that dense E, can form more efficiently and frequently. The present model provides a physical base for understanding the long-term periodicities in occurrence and also the seasonal dependence of strong sporadic E layers at rhidlatitude.