Study On Some Problems Of The Overshoot Effect In The Polar Mesopause

The polar mesosphere in summer is host to a number of fascinating geophysical phenomena that are primarily caused by its extreme thermal structure. Recently, considerable attention has been paid to the anomalously high power radar echoes from the mesosphere at high latitude in summer: the so-called polar mesosphere summer echoes (PMSE). More recently, it was found that PMSE can been strongly affected by a specific cycling of artificial electron heating, when the heater was turned on, the PMSE strength was rapidly weakened or disappeared, then it returned rapidly to approximately the pre-heater value when the heater was turned off, if the heater'off'phase is long enough a strengthening of the PMSE after the initial reduction during the periods of enhanced electron temperatures can been observed, this affect is called the PMSE overshoot effect.We introduce the basic knowledge of PMSE to the above problem and for background purpose, a brief review is given on the conditions of PMSE occurrence and the introduction of the impersonal conditions of the formation of the charged ice particles at mesopause: the mesospheric temperature and humidity. After which, the study on the PMSE occurrence probability variation and the typical feature of the PMSE environment through rocket borne observation are of expatiation.A lot of charged ice particles are detected by the rocket in the polar summer mesopause, which is a kind of dusty plasma and we call the charged ice particles as dust particles. Based on the charging theory of dust particles in the dusty plasmas by P K Shukla, the equation of dust grain charging is formed, and the formula of the ratio of dust charge number to the radius of dusty particle is deduced. Based on the ECT02 campaign, we get the data of the dust charge number density, electron density and temperature. We calculate the ratio of dust charge number to the radius of dusty particle on the assumption that the temperature of electron is much higher than the temperature of ion. Then we compared the ratio with the ratio which we calculated in the case of the temperature of electron equals the temperature of ion. We get that the dust particle is charged more negatively and it's charge increased. Take the variation of the density of electron and ion into account we recalculate the ratio of dust charge number to the radius of dusty particle, which are consistent to the results before.Rocket measurements of electron density profiles in the vicinity of the high-latitude summer mesopause have frequently shown the existence of a sharply bounded layer of thickness ~1 km in which the electron density is depleted by as much as an order of magnitude below the value that would be inferred from the density above and below, also called'bite-outs'. Since the electron density gradients plays a important role in the overshoot effect, we found that'bite-out"indeed have an effect on the overshoot effect. In the end of the paper we analyzed the effect of'bite-out'on the effect overshoot in theory.