On high time‐range resolution observations of PMSE: Statistical characteristics

Abstract

We present observations of polar mesospheric summer echoes (PMSE) with an unprecedented temporal sampling of 2 ms and range resolution down to 75 m. On these time and spatial scales, PMSE exhibit features, like correlation in time and range, that have not been described before. To characterize our high resolution observations, we provide a 4‐D statistical model, based on random processes. In this way we can distinguish between geophysical and instrumental effects on our measurements. In our simulations, PMSE is statistically characterized in frequency, angular space, and inverse altitude. With this model, we are able to reproduce our observations on a statistical basis and estimate the intrinsic spectral width of PMSE. For chosen data sets, such values range between 0.5 Hz and 4 Hz (1.4 ms−1 to 11.2 ms−1). Furthermore, we show that apparent oscillations in time and an apparent high speed motion of the mean scattering center are just representations of the random nature of PMSE measurements on short time scales.

Polar Mesosphere Summer Echoes and Possible Signatures of Pulsating Aurora Detected by the Meteor Radar

“…For the remaining five events, the data are presented in Figures 5a-5e as a color-coded plot showing the amplitudes of the NZ echoes detected during the events as a function of the record duration time (horizontal axis) and the time of detection (vertical axis, the scale is not uniform). This figure shows that the power of the signals appears and reappears on a time scale of the order of 0.5 s, which is very similar to the PMSE observations by Sommer et al (2016).…”

“…A mysterious feature of the pulsating PMSE is the amplitude variations at a frequency of the order of a few Hz. Sommer et al (2016), who were the first to notice this phenomenon, suggested that the variations are caused by the correlation time of the scattering process. They attributed the correlation time to the neutral air turbulence or influence of infrasound, in which cases the variations of the power of radar return are due to interference of reflections from numerous irregularities moving in different directions within the scattering volume.…”

“…Thus, in all the cases, pulsating PMSE occurred during geomagnetic storms. Moreover, the two cases described by Sommer et al (2016) also took place during weak (June 20, 2014) or moderate (June 09, 2015) geomagnetic storms caused by an SI and an HSS, respectively. The same parameters of these events as for those discussed here are given at the bottom of Table 1.…”

Characteristic analysis of layered PMSEs measured with different elevation angles at VHF based on an experimental case

“…To further investigate the generation mechanism of PMSEs, theoretical and experimental studies have been carried out by many researchers (e.g., Hocking et al, 1986;Reid et al, 1988;Pfaff et al, 2001;Zecha et al, 2001;Chilson et al, 2002;Bremer et al, 2006;Smirnova et al, 2010Smirnova et al, , 2011Smirnova et al, , 2012Li Q and Rapp, 2013;Chau et al, 2014;Yi W et al, 2017Yi W et al, , 2018. Sommer et al (2016a) suggest that PMSEs consist of nonhomogeneous isotropic scattering. Furthermore, PMSEs occur in horizontally contiguous areas or patches, which can be smaller than 1 to several kilometers in diameter and which are subject to strong spatial and temporal changes (Sommer et al, 2016b).…”

“…Sommer et al. (2016a) suggest that PMSEs consist of nonhomogeneous isotropic scattering. Furthermore, PMSEs occur in horizontally contiguous areas or patches, which can be smaller than 1 to several kilometers in diameter and which are subject to strong spatial and temporal changes (Sommer et al., 2016b).…”