Meteoroid orbital element distributions at 1 AU deduced from the Harvard Radio Meteor Project observations

Abstract

The orbital element distributions of meteoroids detected during the Harvard Radio Meteor Project, 1968-69 Synoptic Year Program, have been reanalysed to remove selection effects associated with the radar observations. Corrections are made for the observing schedule, antenna beam patterns, the radio diffusion ceiling, speed dependence of ionization production, the flux enhancement due to the Earth's gravity and the probability of encounter with the Earth. These render the eccentricity, aphelion distance, and inclination distributions for meteoroids larger than 10 −4 g (radius ∼200 μm), with orbits that cross the ecliptic near 1 AU.

The sporadic radiant and distribution of meteors in the atmosphere as observed by VHF radar at Arctic, Antarctic and equatorial latitudes

“…The more northern of these appears to have a greater intensity than the southern one, and these sources appear weaker than the helion and anti-helion sources. This is in broad agreement with the studies of Taylor and Elford (1998) and Galligan and Baggaley (2005). Additionally, two weaker sources are observed to lie approximately 60 • above and below the ecliptic plane.…”

“…These represent populations of meteoroids in high inclination orbits. The earlier work of Taylor and Elford (1998) also identify two sources but they place these toroidal sources at higher latitudes than presented here. This is possibly due to differences in techniques used to define the source regions.…”

“…5 is that all six sporadic sources identified by Galligan and Baggaley (2005) are represented. The helion and anti-helion sources (located approximately 70 • to the left and right of the direction of the Earth's motion) are meteoroids in highly elliptical low inclination orbits (Taylor and Elford, 1998) that strike the Earth postperihelion (in the case of helion source) or pre-perihelion (anti-helion source). In addition to these, the apex sources lie approximately 15 • above and below the ecliptic plane.…”

Antarctic meteor observations using the Davis MST and meteor radars

“…This result suggests that the secondary peak is produced predominantly by South Apex sporadic meteors. These results are therefore consistent with the expected speed distributions described by Taylor and Elford (1998), who indicate the Apex meteors have speeds between 50 and 70 km s À1 , while Helion and Anti-helion meteors have speeds between 10 and 40 km s À1 . Fig.…”

“…6a, shows excellent agreement with other specular meteor radar measurements of sporadic meteor distributions (e.g. Cervera et al, 1997;Taylor and Elford, 1998), as well as the BP meteor radar distributions obtained by Holdsworth et al (submitted for publication). However, it is worth mentioning this speed distribution differs from that obtained using high power large aperture (HPLA) radars, which typically show a peak at much larger speeds (e.g.…”