Testing cometary ejection models to fit the 1999 Leonids and to predict future showers

Abstract

Brown & Jones have discussed four models for the ejection velocities of cometary material during the perihelion passage of a comet. The ejection velocities depend on the heliocentric distance, density and mass of the ejected particle and on the size of the comet. For the density of the particles, they assumed three values, 100, 800 and 4000 kg m−3, which give a possible combination of 12 cometary ejection models. This paper tests whether these models can be applied to explain the Leonid phenomenon for which Comet 55P/Tempel–Tuttle is responsible. The ejection is simulated of 61 000 particles during each of the last four apparitions of Tempel–Tuttle, and flux rates on Earth are derived. The results prove that the models with a particle density of 4000 kg m−3 provide the best fit to the observed Leonid rates in 1999. Based on the ejection velocity model that gives the smallest root‐mean‐square error for the year 1999, noticeable displays of the Leonids are predicted for 2000 and 2001 November.

A new method to predict meteor showers

“…The total integration time is about 30 cometary perihelion returns, making in total 7 × 10 6 simulated particles. This is comparable to the Perseid study done by Brown & Jones (1995), and represents much more particles than in the simulations of McNaught & Asher (1999); Göckel & Jehn (2000); Lyytinen & Van Flandern (2000) and Messenger (2002). The two other parameters of Eq.…”

“…Note that this model is not "Crifo (1995)'s model" quoted by Brown & Jones (1998) or Göckel & Jehn (2000). However, this model is closer to the classical "dirty snowball" (Whipple 1950) view of a cometary nucleus.…”

“…A review of several models is given by Brown & Jones (1998). Göckel & Jehn (2000) found that Crifo (1995)'s model best fit Leonid meteor storm observations.…”

“…We store each node "close enough" to the Earth 2 during the numerical integration. Göckel & Jehn (2000) defined two criteria to select the particles encountered by the Earth: a space and a time criterion. The time criterion was used to decrease the statistical weight of particles selected by the space criterion and crossing the ecliptic at a time slightly different from the time of maximum of Leonid shower.…”

“…The time criterion was used to decrease the statistical weight of particles selected by the space criterion and crossing the ecliptic at a time slightly different from the time of maximum of Leonid shower. Brown (cited by Göckel & Jehn 2000) defined this time criterion as ∆T 0.002 yr. This value is taken from the total duration of the Leonid meteor showers ( 2 weeks at most), and is valid as long as the orbit of the meteoroids do not drastically change during this period.…”