Seasonal asymmetry in vertical distribution of meteor decay time at two conjugate polar latitudes

Abstract

The meteor occurrence height and decay time height are strongly dependent on local atmospheric conditions in the mesosphere and lower thermosphere region. In this study, we comparatively examine the seasonal behaviour of vertical distribution of meteor occurrence height and decay time height at two identical radars of conjugate polar latitudes, Esrange (\(68^\circ \)N) and Rothera (\(68^\circ \)S). To understand the nature of meteor trail variations, the received signal power is categorised into two groups, weak and strong echoes, and their seasonal mean vertical profiles are constructed. It has been noticed that the meteor occurrence height shows a seasonal symmetry; however, the decay time vertical profiles show an asymmetric pattern at conjugate polar latitudes, particularly for strong echoes. Seasonally, there is about 1 km difference in the occurrence height and decay time height of weak and strong echoes. From the decay time vertical profiles, it has been noticed that the decay time turning altitude (i.e., inflection point) varies seasonally in the altitude range of 80–86 km for weak and strong echoes. The maximum turning altitude of about 85 km is observed in Northern winter at Esrange (\(68^\circ \)N) and in Southern summer at Rothera (\(68^\circ \)S); similarly, the minimum turning altitude of about 80 km is observed in Northern winter at Esrange (\(68^\circ \)N) and in Southern summer at Rothera (\(68^\circ \)S). The probable reasons for such behaviour of meteor trails at opposite polar latitudes are discussed.