This thesis applies a multistatic meteor radar to an investigation of the dynamics of
the mesosphere lower thermosphere/ionosphere (MLT/I; 60-110 km altitude). The
main radar used in the study operates at 55 MHz and is in the vicinity of Adelaide,
South Australia, consisting of a monostatic radar at the Buckland Park eld site (34.6 S,
138.5 E) and a bistatic receiver located about 55 km south-east at a site in the Adelaide
Hills (35.1 S, 138.8 E). The areas of investigation pertaining to MLT/I dynamics
include assessing the ability of a multistatic meteor radar to measure the vertical
ux
of horizontal momentum and studying the interaction between gravity waves and tidal
e ects. The thesis also presents a novel phase calibration technique for meteor radars,
based on the use of civilian aircraft.
The assessment of this radar's ability to measure MLT/I momentum
uxes demonstrated
that a relative uncertainty of about 75% can be expected for a monostatic con
guration, assuming a
ux magnitude of 20 m2s-2, a single day of integration, and
a gravity wave field synthesized from a realistic spectral model. The multistatic configuration
with a single bistatic receiver is shown to yield a relative uncertainty of about
65% under the same conditions. It is suggested that the increase in precision can be
attributed entirely to the increase in the number of meteor detections associated with
the combined monostatic and bistatic receivers, rather than due to the existence of a
more favourable distribution of Bragg vectors arising from the receiver separation.
A case study of winds around the autumnal equinox of 2018 revealed large modulations
in diurnal tidal amplitudes, with peak component diurnal tide amplitudes of 50
ms-1 and peak zonal wind velocities of 140 ms-1. In the context of the need to verify
the accuracy of momentum
ux estimates from the radar, this motivated an investigation
into the role momentum transport from gravity wave breaking played in modulating the
tidal amplitudes. The investigation showed that while the observed gravity wave forcing
exhibited a complex relationship with the tidal winds, the components of the forcing
were generally seen to be approximately out of phase with the tidal winds above altitudes of 88 km. Additionally, no clear phase relationship between the tides and
gravity wave forcing was observed below 88 km.
Following the case study, the altitude and angle-of-arrival (AOA) errors and reduced
meteor detection rates associated with suspected receiver phase calibration errors motivated
the development of an alternative phase calibration technique. The technique
developed was based on the use of echoes from civilian aircraft with known positions.
Approximately two weeks worth of aircraft detections with the radar and a 1090 MHz
Automatic Dependent Surveillance Broadcast receiver (used to receive aircraft position
information) was acquired during November 2019. By taking into account the implied
phase correction variability with AOA using a beamforming approach, it was shown
that the aircraft-based corrections yielded an equal or smaller meteor height distribution
width than the conventionally used empirical phase calibration technique. Assuming
that a smaller height distribution width equates to smaller average height estimation errors,
this was taken to mean that the aircraft-based approach outperformed the empirical
one.Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 202