"Meteoric phenomena" is the accepted term for the complex of physi- cal
phenomena that accompany the entry of meteoric bodies into the at-
mosphere of the earth (or of any planet). "Meteoric bodies" are usually
defined as cosmic bodies observed by optical or radar techniques, when
they enter the atmosphere. The limiting sensitivity of present-day radar
equipment makes it possible to record meteors of up to stellar magnitude
+14, while the most brilliant bolides may reach magnitude -19. On a mass
7 7 scale this corresponds approximately to a range of 10- to 10 g. How-
ever, met or astronomy is also concerned with larger objects, namely
crater-forming meteorites, or objects that cause large-scale destruction
when they arrive through the atmosphere (an example is the Tunguska
River meteorite). Consideration of the interaction of such objects with
12 the terrestrial atmosphere extends the mass range to 10 g. On the
other hand, scientists studying fragmentation processes in meteoric bod-
7 ies have to consider particles with masses less than 10- g, and the
use of data from meteoric-particle counters on rockets and artificial
satel- lites, from microcraters on the lunar surface, and from
noctilucent clouds 12 lowers the minimum mass to 10- g. Therefore, the
mass range of meteoric bodies, or meteoroids, encompasses 24 orders of
magnitude. Although recent years have witnessed considerable development
in meteor research, both in the Soviet Union and elsewhere, the main
mono- graphs on meteor physics were published twenty or more years ago.