Studying The Phenomenon Of Weakly Ionized Dusty Plasma Heating In The Polar Mesosphere

Polar mesosphere summer echoes(PMSE) are very strong radar echoes occurred close to the polar summer mesopause. At the end of the1970 s, VHF radars operating at frequencies of 50 MHz discovered very strong radar echoes from around the summer mesopause region at altitudes between 80 and 90 km. This phenomenon was first observed by Ecklund and Balsley at Poker Flat,Alaskad. Since then, the PMSE formation mechanism has been most intensely studied. At the beginning of the 1990 s,the high power microwave facility irradiating polar mesosphere(i.e.‘ heating’ polar mesosphere) with the aim to investigate the effects it produce on PMSE. It observed that PMSE intensity could be affected strongly by the artificial electron heating, in the process of heating, PMSE phenomenon disappears, stop heating, PMSE phenomenon reappears. People try to find out the mechanism of PMSE phenomenon from the heating phenomenon, but so far, there has not been a reasonable explanation.It has been discovered that electron number density and dust ice particles number density in polar mesosphere have obvious layered structure along the height.it is shown that there is a close relationship between PMSE and layered structure of electron number density and dust ice particles number density by further research. And the electron density layered structure was caused by dust ice particles, therefore, it lead to an obvious layered structure of dusty plasma dielectric coefficient. According to the electromagnetic wave theory, strong scattering is caused by the dielectric coefficient layered structure. When the polar mesosphere is heated by the high-power microwave heating facility, actually, it is an acceleration process of microwave electric field on electron. As charged particles directional speed can be compared with its thermal speed, the directional movement of charged particles cannot be ignored, the distribution of charged particles in the polar mesosphere obey the double Maxwell distribution.This paper considering the influence of polar mesosphere charged particles directional speed, calculate heated dust particles charge numbers、heated electron number density and dusty plasma dielectric coefficient distribution changes along the height by weakly ionized dusty plasma charging theory based on the double Maxwell distribution. Combined with the layered medium scattering theory, explain reason of PMSE phenomenon disappearance when the high-power microwave facility heating polar mesosphere. The research results have important reference significance for understanding PMSE phenomenon.