Polar mesosphere summer echoes(PMSEs)are very strong radar echoes in the polar mesopause in local summer.Here we present the frequency dependence of the volume reflectivity and the effect of energetic particle precipi...Polar mesosphere summer echoes(PMSEs)are very strong radar echoes in the polar mesopause in local summer.Here we present the frequency dependence of the volume reflectivity and the effect of energetic particle precipitation on modulated PMSEs by using PMSEs observations carried out by European Incoherent SCATter(EISCAT)heating equipment simultaneously with very high frequency(VHF)radar and ultra high frequency(UHF)radar on 12 July 2007.According to the experimental observations,the PMSEs occurrence rate at VHF was much higher than that at UHF,and the altitude of the PMSEs maximum observed at VHF was higher than that at UHF.Overlapping regions were observed by VHF radar between high energetic particle precipitation and the PMSEs.In addition,highfrequency heating had a very limited impact on PMSEs when the UHF electron density was enhanced because of energetic particle precipitation.In addition,an updated qualitative method was used to study the relationship between volume reflectivity and frequency.The volume reflectivity was found to be inversely proportional to the fourth power of radar frequency.The theoretical and experimental results provide a definitive data foundation for further analysis and investigation of the physical mechanism of PMSEs.展开更多
Using PMSE (polar mesosphere summer echoes) observations in combination with particle flux measurements obtained with detectors onboard the Geostationary Operational Environmental Satellite (GOES) a special condit...Using PMSE (polar mesosphere summer echoes) observations in combination with particle flux measurements obtained with detectors onboard the Geostationary Operational Environmental Satellite (GOES) a special condition is shown for the occurrence of rare observed UHF PMSE. When electron flux observed from GOES satellites show a decrease, then after being in the presence of precipitation UHF PMSE occurs. The heating effect on PMSE is small when the UHF electron density is enhanced at 90 km due to particle precipitation. We analyzed and compared the frequency dependence of PMSE under the condition of high energy particle precipitation in July of 2004 and 2007 at well separated frequencies (224 and 930 MHz) at the same site, height, and time. The frequency index varies with height and time. At different heights, the maximum as well as the minimum value of volume reflectivity at VHF is greater than that at UHF with 2 to 3 orders of magnitude. A new qualitative method for the analysis of dust distribution is used by analyzing the relationship between volume reflectivity and frequency index. In agreement with the results of the model it is shown that dust particles of smaller size generally did not occur at the edges, instead they occurred in the middle PMSE regions.展开更多
基金This research was funded by the Sichuan Science and Technology Program(no.2019YJ0188)the National Natural Science Foundation of China(nos.61671116,61771096,11905026)+2 种基金the National Key Research and Development Program of China(no.2019YFA0210202)Fundamental Research Funds for the Central Universities(nos.ZYGX2019Z006,ZYGX2019J012)We are grateful to the EISCAT Scientific Association for providing the PMSE experimental data(http://portal.eiscat.se/schedule/schedule.cgi).The EISCAT Scientific Association is supported by China(China Research Institute of Radio Wave Propagation),Finland(Suomen Akatemia of Finland),Japan(the National Institute of Polar Research of Japan and Institute for Space-Earth Environmental Research at Nagoya University),Norway(Norges Forskningsråd of Norway),Sweden(the Swedish Research Council),and the UK(the Natural Environment Research Council).We also acknowledge the China Scholarship Council.
文摘Polar mesosphere summer echoes(PMSEs)are very strong radar echoes in the polar mesopause in local summer.Here we present the frequency dependence of the volume reflectivity and the effect of energetic particle precipitation on modulated PMSEs by using PMSEs observations carried out by European Incoherent SCATter(EISCAT)heating equipment simultaneously with very high frequency(VHF)radar and ultra high frequency(UHF)radar on 12 July 2007.According to the experimental observations,the PMSEs occurrence rate at VHF was much higher than that at UHF,and the altitude of the PMSEs maximum observed at VHF was higher than that at UHF.Overlapping regions were observed by VHF radar between high energetic particle precipitation and the PMSEs.In addition,highfrequency heating had a very limited impact on PMSEs when the UHF electron density was enhanced because of energetic particle precipitation.In addition,an updated qualitative method was used to study the relationship between volume reflectivity and frequency.The volume reflectivity was found to be inversely proportional to the fourth power of radar frequency.The theoretical and experimental results provide a definitive data foundation for further analysis and investigation of the physical mechanism of PMSEs.
基金supported by National Natural Science Foundation of China (Nos. 41104097 and 41304119)the Fundamental Research Funds for the Central Universities (Nos. ZYGX2015J039, ZYGX2015J037, and ZYGX2015J041)
文摘Using PMSE (polar mesosphere summer echoes) observations in combination with particle flux measurements obtained with detectors onboard the Geostationary Operational Environmental Satellite (GOES) a special condition is shown for the occurrence of rare observed UHF PMSE. When electron flux observed from GOES satellites show a decrease, then after being in the presence of precipitation UHF PMSE occurs. The heating effect on PMSE is small when the UHF electron density is enhanced at 90 km due to particle precipitation. We analyzed and compared the frequency dependence of PMSE under the condition of high energy particle precipitation in July of 2004 and 2007 at well separated frequencies (224 and 930 MHz) at the same site, height, and time. The frequency index varies with height and time. At different heights, the maximum as well as the minimum value of volume reflectivity at VHF is greater than that at UHF with 2 to 3 orders of magnitude. A new qualitative method for the analysis of dust distribution is used by analyzing the relationship between volume reflectivity and frequency index. In agreement with the results of the model it is shown that dust particles of smaller size generally did not occur at the edges, instead they occurred in the middle PMSE regions.