Are meteoroids really dustballs?

Analysis of light curves of faint meteors seem to suggest that most meteoro ids are collections of hundreds to thousands of fundamental grains at least some of which are released prior to the onset of intensive ablation. We wo uld expect these grains, unless extremely uniform in physical properties, t o be aerodynamically separated during flight, and therefore to produce wake , which is defined as instantaneous meteor light production from an extende d spatial region. We present here theoretical results for wake production a s a function of grain mass distribution, height of separation, zenith angle and velocity. In addition, we have obtained observational results from a n ew study which used short duration intensified CCD detectors to search for wake in sporadic meteors. The system employed coaxial intensified CCD camer as at each of two separated stations, one camera utilizing a rotating shutt er and one not at each station. The majority of these nonshower meteors sho wed no statistically significant wake. However, several examples of apparen t transverse separation of the light production regions were found. We also present results of two interesting Leonid meteors from the Mount Allison l ight curve experiment in NASA's 1998 Leonid Multi-instrument Aircraft Campa ign (MAC) program. One of these provide support for the idea of transverse spread in the light production region, up to hundreds of meters, while the other provides a clear case of extreme wake in one Leonid meteor which can only be successfully modeled with very small (approximate to 10(-16)-10(-17 ) kg) constituent grains. (C) 2000 Elsevier Science Ltd. All rights reserve d.