Andrew J. McDonald
La Trobe University
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Publication
Featured researches published by Andrew J. McDonald.
Journal of Geophysical Research | 2014
Emma C. Bland; Andrew J. McDonald; Sebastien de Larquier; John Devlin
A technique for determining key ionospheric parameters from high-frequency (HF) over-the-horizon radar ground scatter data is investigated using two Southern Hemisphere SuperDARN radars and also a Northern Hemisphere SuperDARN radar with reliable elevation angle-of-arrival capability. Ground scatter data are analyzed over a range of frequencies from 8 to 18 MHz to determine the maximum usable frequency and the vertical critical frequency over a wide geographical area within the radar field of view. The technique is shown to be well suited to middle to high latitudes where backscatter echoes from the ground dominate over those from ionospheric scattering targets. However, the technique is shown to break down during the winter months and away from solar maximum. It is shown that the use of reliable elevation angles can greatly enhance such methods allowing discrimination between ground scatter propagating via the E and F regions. It is also shown that contamination from very low velocity ionospheric scatter and ground scatter originating from the back lobe of the radar can be effectively filtered out, with the use of reliable elevation angles. This greatly improves the reliability of the ionospheric data products and allows for a high degree of automation of the process.
Geophysical Research Letters | 2014
Emma C. Bland; Andrew J. McDonald; F. W. Menk; John Devlin
We present a technique for the automatic detection of Pc5 (150 s to 600 s period) ultralow frequency (ULF) pulsations in ground and ionospheric backscatter from the Super Dual Auroral Radar Network (SuperDARN). This new technique enables rapid identification and visualization of ULF oscillations over the very wide geographical coverage of SuperDARN. The technique detects ULF oscillations using the Lomb-Scargle periodogram method, which provides a natural test for periodic behavior against the null hypothesis of a pure noise distribution. This does not require any interpolation across data gaps and is thus appropriate for SuperDARN data. We demonstrate the application of the technique to SuperDARN data for March 2014 and find that Pc5 pulsations are frequently observed by multiple radars simultaneously. A preliminary investigation using data from all Northern Hemisphere SuperDARN radars indicates that Pc5 pulsation activity occurs most often on the nightside of the magnetosphere, with a mean frequency of about 2 mHz.
computational science and engineering | 2014
Clarence Goh; John Devlin; Dennis Deng; Andrew J. McDonald; Muhammad Ramlee Kamarudin
Super DARN operating frequencies from 10MHz-15MHz are susceptible to clutter originating from unwanted altitude backscatter, man-made noise exhibiting a Gaussian distribution and correlated speckle noise from pulses emitted from other similar Super DARN radars operating at the same frequency. The paper focuses on removing man-made clutter and uncorrelated speckle noise noise by prior measurement of received noise signal. Based on noise information, an uncorrelated weighted median filter is proposed and used to remove unwanted clutter.
ieee international radar conference | 2013
Edhem Custovic; Darrell Elton; Jim Whittington; John Devlin; Adam Console; B. Bienvenu; Andrew J. McDonald; Hieu T. Nguyen
This paper presents a novel antenna impedance matching system used in the latest Australian SuperDARN class HF radar, at Buckland Park, South Australia. Earlier radar designs used an off-the-shelf log-periodic wideband antenna that is significantly easier to match over the SuperDARN frequency band, but expensive to buy and mount, and had limited capability for azimuthal beamforming. The newer TTFD antenna, used in many recent SuperDARN radars, offers improvement in these areas, but is in essence a narrow band antenna. It is capable of wideband operation at the cost of being difficult to match, frequency dependant, high-impedance and complex load. Previous TTFD matching transformers utilising toroids have been measured and evaluated for their suitability for the Buckland Park radar. A new system based on an LC matching network circuit has been devised to replace them. The design approach and results of the new matching circuit are detailed.
Radio Science | 2013
Andrew J. McDonald; Jim Whittington; Sebastien de Larquier; Edhem Custovic; Thomas A. Kane; John Devlin
Journal of Atmospheric and Solar-Terrestrial Physics | 2012
Brett Anthony. Carter; Roman A. Makarevich; John Devlin; Andrew J. McDonald
Radio Science | 2013
Edhem Custovic; Andrew J. McDonald; Jim Whittington; Darrell Elton; Thomas A. Kane; John Devlin
Journal of Geophysical Research | 2016
Emma C. Bland; Andrew J. McDonald
Journal of Geophysical Research | 2016
Emma C. Bland; Andrew J. McDonald
Radio Science | 2013
Andrew J. McDonald; Jim Whittington; Sebastien de Larquier; Edhem Custovic; Thomas A. Kane; John Devlin