| Abstract: | 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. |
