Altitudinal and latitudinal asymmetry in diurnal variation of sporadic meteor flux observed over Thumba

Abstract

We present here latitudinal dependence of the diurnal variation of the sporadic meteor flux rate based on radar observations made from Thumba (8.5°N, 77°E), Darwin (12.5°S, 130.8°E), Buckland Park (34.4°S, 138.3°E) and Davis (68.6°S, 78.0°E). The most striking observation was the occurrence of a secondary peak at Thumba at 03:00 local time (LT) prior to the occur- rence of the commonly observed morning peak at 06:00 LT at all altitudes. Surprisingly, the secondary peak was not observed at Darwin, which is a low- latitude station close to Thumba, but in the southern hemisphere. Further, we found that this secondary peak has a clear seasonal variation. In summer (win- ter), the primary (secondary) peak is larger than the secondary (primary) peak and they are comparable in the equinoxes. The observed diurnal rates also showed seasonal and latitudinal variabilities, which can be interpreted in terms of observing geometry of the spo- radic meteor sources in the local sky. Our observations also suggest that there exists asymmetry in northern and southern hemisphere sporadic meteor flux.