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Re: (meteorobs) Bradfields
On Mon, 3 Mar 2003, H.Luethen wrote:
> ejected at a certain range of velocities. But small particles are
> displaced after ejection along the trail by solar radiation
> pressure to positons corresponding large delta a0 values,
> whereas large particles are not so much affected and remain
> where they are, at low delta a0 values. So a kind of
> sorting takes place after ejection.
Yes, this is correct. I rather glossed over this in my message with a
single sentence. Note that there is a common misconception that solar
radiation pressure (srp) "blows the particles away from the Sun" with the
belief that the perihelion distance increases every time the particle
comes around. This is incorrect. Srp simply decreases the effect of the
Sun's gravity and the particle orbits in a different ellipse (or in the
case of very small particles, a hyperbola) to a particle with a smaller
effect from srp. It would thus continue to follow its initial orbit
were it not for the effect of planetary perturbations (which effect all
particles equally) and that there are unquestionably additional
non-gravitational effects at play. Esko Lyytinen has modeled such effects
in his theory.
> The position at which the earth intersects the trail corresponds
> to a certain delta a0 value (or a certain ejection velocity in
> terms of the very simple model). If this delta a0 is quite low
> and the trail is quite old, you may expect to find only the
> larger particles left, the smaller ones having been "blown away".
I'm not sure if Hartwig is falling into this erroneous belief here, or if
he is referring to these other non-gravitational effects which
unquestionably act to diffuse dust trails. These effects should act more
strongly on smaller particles. At the point of ejection, the orbital
periods of particles become fixed (ignoring the effects of
non-gravitational effects other than srp), so the ratio of particle sizes
would remain fixed and be a function of da0 regardless of age. However
the various additional non-gravitational forces act to diffuse the smaller
particles both by changing their orbital period and broadening the trail,
so Hartwig's comment on age being a factor is correct.
> Having not read the paper I suspect that this was meant.
My comment was my own interpretation of what happens at ejection and was
unrelated to Kozai's paper.
Hartwig refers to "a simple model". The use of ejection along the
heliocentric velocity vector of the comet at perihelion is often
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