On the angular dependence and scattering model of polar mesospheric summer echoes at VHF

摘要

abstract_textpWe present measurements of the angular dependence of polar mesospheric summer echoes (PMSE) with the Middle Atmosphere Alomar Radar System in Northern Norway (69.30 degrees N, 16.04 degrees E). Our results are based on multireceiver and multibeam observations using beam pointing directions with off-zenith angles up to 25 degrees as well as on spatial correlation analysis (SCA) from vertical beam observations. We consider a beam filling effect at the upper and lower boundaries of PMSE in tilted beams, which determines the effective mean angle of arrival. Comparing the average power of the vertical beam to the oblique beams suggests that PMSE are mainly not as aspect sensitive as in contrast to previous studies. However, from SCA, times of enhanced correlation are found, indicating aspect sensitivity or a localized scattering mechanism. Our results suggest that PMSE consist of nonhomogeneous isotropic scattering and previously reported aspect sensitivity values might have been influenced by the inhomogeneous nature of PMSE./p/abstract_text