LABORATORY AND IN-SITU EVIDENCE FOR THE PRESENCE OF ICE PARTICLES IN A PMSE REGION

An interpretation is made of rocket data obtained from an electric fie ld mill (EFM) sensor during the international rocket-radar campaign NL C-91. The interpretation is based on a laboratory study of the interac tion of a water particle beam with the EFM recovered after the rocket flight. Both rocket and laboratory data show that the field mill is se nsitive to ice microparticle impacts and that perturbations in the EFM signal observed in the vicinity of noctilucent clouds and an enhanced radar echo (PMSE) layer are caused not only by atmospheric electric f ields but also by the impact of solid particles. The altitude range of the impact signatures suggests the presence of ice particles in the P MSE region above the height of the optically detected noctilucent clou ds. The analysis of the rocket data on the basis of the laboratory res ults allows us to estimate sizes of these PMSE particles to be 13 - 40 nm.