Cosmic Dust Measurements
|It is estimated that nearly 44
metric tons of meteoric material enter the Earth’s atmosphere daily [Hughes, 1975; Millman, 1975]. Approximately
70% of the incident meteoroids are vaporized due to heating during
atmospheric entry at altitudes between 80 and 100 km. Meteorites
are the surviving portion of a meteoroid, and micrometeorites are
particles that are too small to reach their boiling point.
Meteoric materials are oxidized by collision with atmospheric O2, and
vapor resulting from meteoroid ablation condenses to form “smoke”
particles in the mesosphere [e.g., Rosinski
and Snow, 1961; Hunten et al.,
1980]. The composition of incident meteoroids is similar to
carbonaceous chondrites containing an abundance of volatile elements
including silicon, magnesium, and iron. While the incident mass
of cosmic material is primarily from meteoroids with radii between 50
and 500 μm [Millman, 1975],
the suspended atmospheric mass exists primarily as smoke particles with
radii between 0.2 and 10 nm [Hunten
et al., 1980].
The ability of SOFIE measurements to detect the cosmic smoke layer in the mesosphere has been investigated. Model calculations of smoke particle size distributions and recent in situ smoke measurements from MAGIC were used with the optical constants of various smoke analogues to simulate smoke signals at the SOFIE wavelengths. The results (Figure 1) indicate that the 0.86 micron extinction is a factor of 30 above the digitization limit, and show difference signals of nearly 3000 counts. These results suggest that SOFIE could provide the first satellite remote measurements of the cosmic smoke layer.
Figure 1. Simulated smoke signals for SOFIE channel 2 based on a modeled particle size distribution profile from CARMA scaled to recent in situ smoke particle concentration measurements from MAGIC. Particle extinctions were calculated using Mie theory with the refractive indices for carbon particulates.
A presentation on SOFIE measurements of the cosmic smoke layer.