Estimating neutral density of the thermosphere from meteor trajectories

Abstract:

Meteoroids are naturally occurring solid bodies in space that can range from dust sized particles that are tens of microns in diameter up through about meter in size. Those that enter the Earth's atmosphere provide a source of extraterrestrial metallic ions deposited into the atmosphere, and also serve as probes that can allow us to infer the atmospheric conditions being traversed. Observations of atmospheric neutral density and associated dynamics within the mesosphere/lower thermosphere (MLT) region, encompassing roughly 50 to 120 km altitude, has been challenging due to its inaccessibility to balloon-borne or orbital in situ instruments. In this region, meteoroids experience deceleration and ablation due to atmospheric collisions, resulting in the formation of plasma known as meteors. High-Power Large-Aperture (HPLA) radar can track the head plasma of the meteor, which moves with the parent meteoroid, to determine the deceleration of the meteoroid subject to drag and ablation. Multiple meteors passing through the same altitude layers provide input to an inversion technique to estimate the neutral density of the atmosphere being traversed.

We conducted a coordinated experimental campaign to collect meteor data that we can use to study latitudinal coupling in neutral densities. This campaign used three HPLA facilities at similar longitude spanning latitudes from Jicamarca Radio Observatory (JRO) in the equatorial region to Resolute Bay (RISR-N) in the polar region, with measurements at mid-latitude from Millstone Hill Observatory (MHO). Example meteors seen from each radar facility are presented in the attached figure. We present current results on population statistics of the detected meteors, and on signal processing techniques applied to obtain high-precision trajectories from the meteors detected.

This research is supported by NSF Grant AGS-1920383.