Statistical analysis of meteoroid fragmentation during the Geminid and Leonid meteor showers

Abstract

The meteoroid disintegration mechanism is a subject of interest as they are the sources for metallic layers in MLT region, ionsopheric sporadic E, Noctilucent clouds and other aeronomy. It is known that meteoroid mass is deposited in the upper atmosphere either through fragmentation or through differential and simple ablation mechanisms. Each mechanism deposits the flux in different form (dust/ smoke-fragmentation, atomic form-ablation). Both the Leonid Meteor Shower (LMS) (parent body-Comet 55P/ Tempel - tuttle) and Geminid Meteor Shower (GMS)(parent body Asteroid- Phaethon 3200) are observed using MST Radar at NARL, Gadanki (13.5N, 79.2E). The atmospheric sodium density during the Geminid Meteor shower (GMS) is estimated using co - located sodium LIDAR. The ablation and fragmentation mechanisms of the meteoroid influx during these showers are studied using RTI plots from In phase and Quadrature channels of MST Radar, Signal to Noise Ratio (SNR) by estimating moments and line of sight velocities. Our observations using MST Radar disclosed an important outcome that the asteroid originated meteoroids (Geminids) are undergoing less fragmentation when compared to comet originated meteoroids (Leonids). The fragmentation percentage estimated during the GMS is 14 % which is significantly lower than 20%, estimated for LMS. During GMS using Na LIDAR, it is also observed that the concentration of metallic sodium in ionosphere E - Region increased on peak activity day compared to pre peak day. The line of sight velocities plotted for down the beam echoes during the showers dominantly followed a smooth evolution in altitude and time, before and after the occurrences of SNR changes, indicating that the meteoroids did not undergo any abrupt physical modification such as fragmentation. Further enhancement of atomic Na concentrations in E - region ionosphere during the shower indicates the flux deposition due to ablation. After comparison it is found that the dominant meteoroid disintegration mechanism for Geminids is likely the ablation unlike the LMS. We speculate here with substantial evidence that the contribution of fragmenting meteoroids in differently originated meteoroid showers is different and may be attributed to the chemical composition of their parent bodies of the meteoroids from which they are originated. This outcome has importance of its own as their parent bodies are different, the former shower being asteroid originated and the later comet originated. These results will also contribute in improving current meteoroid single body/dust ball ablation models.