A semi-empirical model of the contribution from sporadic meteoroid sources on the meteor input function in the MLT observed at Arecibo

In this paper, we present a modeling and observational study of the micrometeor input function with a focus on understanding how each of the extraterrestrial sporadic meteoroid sources contributes to the observed meteoric flux in the Mesosphere and Lower Thermosphere (MLT) atmospheric region. For this purpose, we expand the model presented by Janches et al. (2006) using a Monte Carlo technique and incorporating: 1) a widely accepted global mass flux, which is divided into different proportions among the known sporadic meteoroid sources as the initial input above Earth's atmosphere; 2) contemporary knowledge on the source's velocity and radiant distributions; and 3) the full integration of the canonical meteor equations that describe the meteoroid entry and ablation physics. In addition, we constrain the initial input through a comparison of our modeled results with meteor observations obtained with the 430 MHz High Power and Large Aperture (HPLA) Arecibo radar in Puerto Rico that covers all seasons. The predicted meteor rates and velocity distributions are in excellent agreement with the observed ones without the need for any additional normalization factor. Our results indicate that although the Earth's Apex centered radiant source, which is characterized by high geocentric speeds (similar to 55 km/s), appears to be similar to 33% of the meteoroids in the Solar System at 1 AU, it accounts for similar to 60% of the meteors observed by the Arecibo HPLA radar in the atmosphere. The remaining 40% of observed meteors originate mostly from the Helion and Anti-Helion sources, with a very small, but constant during the day, contribution of the South and North Toroidal sources. These results also suggest that particles smaller than similar to 10(-3) mg with slow velocities (< 30 km/s) will not significantly ablate and never become observable meteors. The motivation of this effort is to construct a new and more precise MIF model needed for the subsequent modeling of the atmospheric phenomena related to the meteoric flux.