Prediction of Size of Iron Spherules Formed from Melted Micrometeoroids

Abstract

Movement of liquid iron micrometeoroid in the Earth atmosphere is simulated to find the time-dependence of its acceleration, velocity and coordinates as well as the length of luminous trajectory when the micrometeoroid is still melted. In the simulations it is assumed that the maximum size of the stable droplet is determined by aerodynamic fragmentation of the moving droplet occurring when the Weber number exceeds its critical value. Two different initial altitudes h of droplet formation were analysed: 80 km and 50 km, both for a wide range of initial velocities between 6 and 20 km/s. Depending on their initial velocity, exceeding the Earth’s escape velocity equal 11.2 km/s, the maximum radius of solid spherules, emerging from solidified final droplet, is predicted here to lie between (a) 55 and 100 μm for h = 80 km, and (b) 10 and 30 μm for h = 50 km.

Keywords

• droplet size
• liquid micrometeoroids
• iron spherules
• aerodynamic fragmentation
• weber number