Abstract
Observations of atmospheric neutral density and associated dynamics
within the lower thermosphere has been a challenge to the atmospheric
science and space community due to its inaccessibility to balloon-borne
or orbital in situ instruments. We present a methodology to study the
latitudinal and temporal variation of neutral density in this region
through a simultaneous campaign at geographically distinct high-power
large-aperture (HPLA) radar facilities to observe meteor trajectories.
These meteors are formed by meteoroids entering the Earth’s atmosphere;
the deceleration they undergo due to atmospheric drag provides a source
of information to determine the neutral density of the atmosphere at
altitudes of 80 to 140 km. Through the measurement of meteor head echo
trajectories using specialized radar waveforms and signal processing to
enhance the range resolution, combined with novel statistical techniques
to account for the distribution of meteoroid properties, the temporal
evolution of atmospheric neutral density from 70 to 140 km can be
characterized with sub-km altitude resolution. Initial results will be
presented from the first of four observation campaigns planned during
the 2019-2021 period using the HPLA radar sites at Jicamarca, Millstone
Hill, and Resolute Bay, which span equatorial to polar latitudes at
similar longitude. The simultaneous measurements across facilities
complements other measurements of atmospheric composition and structure
at similar altitudes to provide improved identification of latitudinal
coupling and forcing from lower altitudes into the
magnetosphere-ionosphere-thermosphere (MIT) system.