Experimental Measurements of the Ionization Coefficient (β) for Silicon and Iron Micrometeoroids During Ablation in Air and N2
Earth constantly receives micrometeoroids from asteroids and comets. Studying their mass flux is essential
because these particles inject metals into the atmosphere and represent a potential risk for spacecraft. While
entering the Earth, meteoroids are subject to ablation, a process where the particles are eroded and vaporized.
Hyperthermal collisions between ablated meteoric chemical compounds and air molecules take place. This
produce ion-electron pairs as well as photons which leads to the formation of light and plasma. Ground-
based radar systems detect micrometeoroids through the ionized plasma produced during this process.
A key parameter in the ablation process is the ionization coefficient (β), which characterizes the ionization
produced during meteoroid–atmosphere collisions. This parameter is required to estimate meteoroid mass
flux, densities, masses and height distribution from radar observations. Previous studies have developed
semi-empirical models of β for Fe and Al. However, reliable measures for additional elements and materials
are needed in order to improve model accuracy.
The University of Colorado Boulder has developed a dust electromagnetic accelerator that recreates the
ablation of submicrometer particles under controlled laboratory conditions. In this instrument, particles are
accelerated into a gas-filled cell at velocities between 1 and 80 km/s. The cell is equipped with 16 charge
collectors that measure the charge generated during particle ablation, allowing β to be derived from the
measured signals.
In this work, we used University of Colorado facilities to calculate new experimental values of β for Si and
to expand existing measurements for Fe. Si particles were accelerated to velocities between 10 and 50 km/s
in air and N2, while Fe particles were accelerated between 8 to 20 km/s. The data obtained were compared
with previous models and previous experimental measurements. These new measurements improve the
accuracy of β models and provide a better understanding of the ablation process. These results will improve
the radar detection models and enhance the characterization of micrometeoroids entering Earth’s atmosphere.