English
norskBlar i forfatter "McKay, Derek"
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Auroral classification ergonomics and the implications for machine learning
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-07-09)The machine-learning research community has focused greatly on bias in algorithms and have identified different manifestations of it. Bias in training samples is recognised as a potential source of prejudice in machine learning. It can be introduced by the human experts who define the training sets. As machine-learning techniques are being applied to auroral classification, it is important to identify ... -
Auroral Image Classification With Deep Neural Networks
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-05)Results from a study of automatic aurora classification using machine learning techniques are presented. The aurora is the manifestation of physical phenomena in the ionosphere‐magnetosphere environment. Automatic classification of <i>millions</i> of auroral images from the Arctic and Antarctic is therefore an attractive tool for developing auroral statistics and for supporting scientists to study ... -
KAIRA - The Kilpisjärvi Atmospheric Imaging Receiver Array
(Doctoral thesis; Doktorgradsavhandling, 2018-08-24)The Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) is a phased-array radio detector located in Arctic Finland, where auroral electron precipitation is common. This unique deployment of a modern radio telescope in an unconventional location has resulted in a novel and powerful instrument capable of carrying out a large variety of remote-sensing, geoscience experiments. This work presents a ... -
KAIRA Science Results
(Conference object; Konferansebidrag, 2018) -
Low-frequency radio absorption in Cassiopeia A
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-08)<i>Context</i>: Cassiopeia A is one of the best-studied supernova remnants. Its bright radio and X-ray emission is due to shocked ejecta. Cas A is rather unique in that the unshocked ejecta can also be studied: through emission in the infrared, the radio-active decay of <sup>44</sup>Ti, and the low-frequency free-free absorption caused by cold ionised gas, which is the topic of this paper.<p> ... -
Lumikot: Fast auroral transients during the growth phase of substorms
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-25)The development of a magnetospheric substorm may be classified into three phases: growth, expansion, and recovery. The growth phase is important as it includes processes that lead to the expansion. In a recent growth-phase study, a type of fast discrete auroral transient phenomena -- referred to as Lumikot -- were observed. The Lumikot are several kilometers across and move in the high-energy ... -
Manx Arrays: Perfect Non-Redundant Interferometric Geometries
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-09)Interferometry applications (e.g., radio astronomy) often wish to optimize the placement of the interferometric elements. One such optimal criterion is a uniform distribution of non-redundant element spacings (in both distance and position angle). While large systems, with many elements, can rely on saturating the sample space, and disregard “wasted” sampling, small arrays with only a few elements ... -
Multi-static spatial and angular studies of polar mesospheric summer echoes combining MAARSY and KAIRA
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-06)Polar mesospheric summer echoes (PMSEs) have been long associated with noctilucent clouds (NLCs). For large ice particles sizes and relatively high ice densities, PMSEs at 3m Bragg wavelengths are known to be good tracers of the atmospheric wind dynamics and to be highly correlated with NLC occurrence. Combining the Middle Atmosphere ALOMAR Radar System (MAARSY) and the Kilpisjärvi Atmospheric Imaging ... -
On the determination of ionospheric electron density profiles using multi-frequency riometry
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-27)Radio wave absorption in the ionosphere is a function of electron density, collision frequency, radio wave polarisation, magnetic field and radio wave frequency. Several studies have used multi-frequency measurements of cosmic radio noise absorption to determine electron density profiles. Using the framework of statistical inverse problems, we investigated if an electron density altitude profile ... -
Pulsating aurora and cosmic noise absorption associated with growth-phase arcs
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-18)The initial stage of a magnetospheric substorm is the growth phase, which typically lasts 1–2 h. During the growth phase, an equatorward moving, east–west extended, optical auroral arc is observed. This is called a growth-phase arc. This work aims to characterize the optical emission and riometer absorption signatures associated with growth-phase arcs of isolated substorms. This is done using ... -
Shock location and CME 3D reconstruction of a solar type II radio burst with LOFAR
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-19)<p><i>Context - </i>Type II radio bursts are evidence of shocks in the solar atmosphere and inner heliosphere that emit radio waves ranging from sub-meter to kilometer lengths. These shocks may be associated with coronal mass ejections (CMEs) and reach speeds higher than the local magnetosonic speed. Radio imaging of decameter wavelengths (20–90 MHz) is now possible with the Low Frequency Array ...
