36th DPS Meeting, 8-12 November 2004
Session 34 Comets: Nuclei, Tails, Solar Wind
Poster II, Thursday, November 11, 2004, 4:15-7:00pm, Exhibition Hall 1A

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[34.15] An Updated Velocity Distribution for Meteoroids at the Earth

P. Brown, R. Weryk (Dept. of Physics and Astronomy, University of Western Ontario, London, Canada), M. Campbell-Brown (Dept. of Geophysics, University of Calgary, Calgary, Alberta, Canada)

The accepted velocity distribution of meteoroids at 1 A.U. has been measured through radar and photographic observations of meteors in Earth’s atmosphere. The smaller statistical size of photographic meteor observations and large biases in earlier radar studies have called into question the veracity of the presently accepted meteoroid velocity distribution (cf. Taylor and Elford, 1998). In an effort to measure the true out-of-atmosphere velocity distribution of meteoroids in the tens of microgram mass range, we have performed velocity measurements using the Canadian Meteor Orbit backscatter radar employing the time-of-flight (TOF) velocity technique. This technique does not experience selection biases against fragmenting meteoroids as suffered by earlier surveys such as the Harvard Radio Meteor Project. We have debiased our raw velocity measurements taking into account individual radiant collecting areas, the ionization-velocity dependence, diffusion, initial trail radius attenuation and the finite velocity effect (Ceplecha et al., 1998). We have also applied a new empirically derived correction for radar meteor deceleration as a function of velocity and height calibrated using showers with known velocities. Using a total of more than 1.5 million velocity measurements collected over a 30 month time period, we have found a higher proportion of fast (>40 km/s) meteoroids than previously measured. We will present both our debiased velocity distribution and the true inclination distribution of interplanetary meteoroids at 1 AU based on these observations.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.