METEOROID PICTURE FREE

Numerical modeling suggests that the stone skipping–like trajectory associated with a shallow entry angle (e.g., ~6.5° to 7.3°) is responsible for Aletai’s exceptionally long strewn field if a single-body entry scenario is considered. Petrographic and trace elemental studies suggest that all the Aletai masses exhibit unique compositions (IIIE anomalous), indicating that they were from the same fall event. This implies that the dynamics of Aletai could be unique. Nevertheless, the recently found massive Aletai irons in the northwest China comprise the longest known strewn field of ~430 kilometers. It typically has a length of several to a dozen kilometers. Strewn field, as a product of meteoroids/asteroids breakup, comprehensively reflects the trajectory, dynamics, and physical properties of meteoroids/asteroids. Meteoroids/asteroids could deposit energy to Earth during their entries, which arouses great concerns. This paper reviews existing ablation models and discusses model boundaries.

METEOROID PICTURE FREE

Several self-consistent hydrodynamical models are developed, but similar models for transition and free molecule regimes are still under study. Ablation models should make it possible to describe physical conditions that occur around meteor body. These evaporated particles form initial train, which then spreads into an ambient air due to diffusion. Classic approach to meteor interaction with atmosphere allows describing two limiting cases:-large meteoroid at relatively low altitude, where shock wave is formed (hydrodynamical models) -small meteoroid/or high altitudes-free molecule regime of interaction, which assumes no collisions between evaporated meteoroid particles. Local flow regime realized around the falling body determines the heat transfer and mass loss processes. Fast meteoroids (V>30-40 km/s) may lose a part of their material at higher altitudes due to sputtering. Meteoroids of cometary origin typically have higher termination altitude due to substance properties and higher entry velocity. Larger bodies (up to meter sizes) penetrate deeper into the atmosphere (down to 20 km altitude). Material from ablation of small-sized meteors (roughly R£0.01-1 cm) is mostly deposited between 120 and 80 km altitudes.

The fate of entering meteoroids in atmosphere is determined by their size, velocity and substance properties.

Meteoroid picture