Interplanetary Particles and Noctilucent Clouds

Abstract

The equation of motion of a small spherical particle, entering the earth's atmosphere with cosmic velocities, has been integrated numerically. The results show that particles in the size range 0.1-100 ? attain terminal velocities around 80-100 km altitude where noctilucent clouds are observed. Results of a rocket collection experiment indicate that the high g loads experienced by the larger particles during their entry into the atmosphere, may cause fragmentation and thus further increase the small particle population in that region.