ИСТИНА

MF radar observations of mesospheric backscatter were carried out during summer 1999 at Tumanny (69.0N, 35.7E) using the PGI radar of vertical radiation. The MF radar was operated with peak power of ~ 100kW, a frequency - 2.72 MHz, a range resolution of 2.25 km. The antenna array consisted of 32 (4x8) extended range cross vibrators with a rotating field polarization and was suitable for transmission and rece tion of radiowaves. The beam width ~ 19o (north - east) and 30o (north-west). The observations indicated the presence of intensive radioreflections from mesospheric layers at the altitudes range of 74-99 km. Usually, these reflections look like as 2 or 3 of distinct layers, which located at heights 71-82, 82-89 and 89-99 km The features of MF radioreflections from altitudes between 82-89 km are very similar to VHF radar measurements of Polar Mesosphere Summer Echoes (PMSE). The distinctive feature of these observations was a registration of the sharp gradients of electron density at the same heights, where reflections were more intensive. An analysis of digital ionograms in Loparskaya (68.6N, 33.3E) have shown that intensive sporadic E-layers observed during strong MF radar returns appearance from the mesopause region.