Inter-Hemispheric Comparison of Meteor Decay Time and Its Derived Parameters at 68° Latitudes

The decay time of underdense meteor echoes is highly sensitive to background atmospheric conditions in the mesosphere and lower thermosphere (MLT)-region. Using long-term observations from two identical SKiYMET meteor radars located at conjugate polar latitudes, Esrange (68°N, 21°E, 2005–2022) and Rothera (68°S, 68°W, 2005–2024), we examine the inter-hemispheric similarities and differences in meteor decay time and decay time derived atmospheric parameters. The analysis reveals strong hemispheric resemblance in the seasonal evolution of peak meteor occurrence height and broad decay-time distributions, but also clear differences in vertical structure and seasonal amplitude. Mesopause temperatures exhibit a distinct seasonal phase shift between the hemispheres, with consistently higher summer peak heights and larger seasonal ranges at Rothera. Lomb-Scargle spectral analysis confirms that annual and semiannual oscillations dominate temperature variability at both sites, with weaker higher-order periodicities contributing to secondary modulation. Seasonal profiles of weak and strong meteor echoes show contrasting behaviors, particularly in the altitude of maximum decay time and the turning altitude of decay-time profiles. These results demonstrate that decay-time parameters provide a sensitive diagnostic of hemispheric differences in mesospheric structure and reveal fundamental asymmetries in MLT dynamics at conjugate polar latitudes.