Time evolution of ionospheric D-region plasmas including the perturbations of electrons and charged aerosol particles is investigated under the conditions of polar mesosphere summer echoes （PMSE）. It is shown that the time scale of decay of the electron density is in the order of an hour under typical PMSE conditions, in the majority of cases, the electron density is anticorrelated to the ion density, except that the radius of aerosol particles is greater than 50 nm. Also, the evolutions under varied parameters, such as the amplitude and width of perturbation, the aerosol particle radius, and the altitude of the PMSE occurrence are investigated. The obtained results are useful for interpreting the experimental observations.
Polar mesosphere summer echoes （PMSE） are very strong radar echoes from alti- tudes close to the polar summer mesopause. The data from sounding rocket campaigns indicate that the radar signal to noise ratio （SNR）, electron density and dust charge density of polar meso- sphere in summer show obvious layered structure. In this paper the theory of wave propagation in layered media is used to study the reflectance and SNR at each layer in polar mesosphere. The calculated SNR using theory of dusty plasma is found in good agreement with the experimental result, which may imply that the intensity of the radar echoes reflected by the layered structure in polar mesosphere where polar mesosphere summer echoes used to occur can interpret partially the phenomenon of PMSE. In other words, reflection may play an important role in the occurrence of PMSE.
Observation data recorded by the European Incoherent Scatter Scientific Association in TromsФ, Norway in August 2009 were analyzed to determine the heating effects in polar summer ionospheric modification experiments. There are two types of increases in electron temperature： large relative increases in a narrow range near 150 km and greater absolute increases in a wider range at 150-400 km. The percentage increase in temperature linearly increases with heating power, but the rate of increase decreases with increasing pump frequency. A clear two-dimensional distribution was found for the measurement made on August 15, and the beating effects are greater closer to the direction of the geomagnetic field. The heating effects obviously depend on the angle between the heating beam and geomagnetic field; as the angle increases, the heating effect decreases.
