Dr Gareth Dorrian: Publications

Radio Astronomy, the Earth’s Atmosphere and Geometric Optics: A Hands-On Activity for Secondary School Students

(2025)

Authors:

Alan Wood, Gareth Dorrian, Ben Boyde, Richard Fallows

Abstract:

The Low Frequency Array (LOFAR) is one of the most advanced radio telescopes in the world. When radio waves from a distant astronomical source pass through the Earth’s upper atmosphere, plasma structures act as lenses. The refraction of these radio waves, and their subsequent interference, significantly affects the received signal. Activities have been developed for secondary school students aged between 16-18 based on these observations.Students are given research data from LOFAR and work in groups to interpret these observations, drawing on material from both geometric optics and astronomy. They are also introduced to key research skills, such as how to create a numerical definition of a phenomena which is clear, rigorous and well-documented. These activities were developed with reference to the Oxford, Cambridge and RSA Exam Board A-level Physics Specification in the UK. They have been trialed and refined in a secondary school, are now made available to the wider community.

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Statistics of Small-Scale Ionospheric Waves in European Mid-Latitudes Observed Using LOFAR

(2025)

Authors:

Ben Boyde, Alan Wood, Gareth Dorrian, Francesco de Gasperin, Frits Sweijen, Maaijke Mevius, Kasia Beser

Abstract:

The LOw Frequency ARray (LOFAR) is a radio telescope centred in the Netherlands. The observed impact of the ionosphere on signals from astronomical radio sources can be used to derive differential Total Electron Content (dTEC) between the lines of sight from different LOFAR stations. The dTEC derived in calibration has extremely high precision (~1 mTECu) and is available at high temporal (~4s) and spatial (baselines from ~100 m to ~100 km) resolutions. These measurements provide a new means of studying ionospheric disturbances in the mid-latitudes.A method for identifying wave signatures in the dTEC data has been developed and shown to be capable of identifying waves with amplitudes as low as a few mTECu (Boyde et al., 2023). This method has been used to analyse over 2,500 hours of observations made as part of an astronomical survey. The statistical characteristics of the identified waves and their dependence on time of day, season, and geomagnetic activity are discussed, such as variations in dominant propagation direction. These observations extend the range of ionospheric waves that can be identified to shorter wavelengths and lower amplitudes beyond what is currently detectable using GNSS derived TEC. This method complements established techniques for detecting ionospheric waves.Ben Boyde, Alan George Wood, Gareth Dorrian, et al. Wavelet Analysis of Differential TEC Measurements Obtained Using LOFAR, Radio Science (Under Review), 2023, doi: 10.22541/essoar.169754969.93126117/v

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Statistics of travelling ionospheric disturbances observed using the LOFAR radio telescope

Journal of Space Weather and Space Climate EDP Sciences 15 (2025) 6-6

Authors:

Ben Boyde, Alan G Wood, Gareth Dorrian, Francesco de Gasperin, Maaijke Mevius

Abstract:

A climatology of Travelling Ionospheric Disturbances (TIDs) observed using the LOw Frequency ARray (LOFAR) has been created based on 2723 h of astronomical observations. Radio telescopes such as LOFAR must contend with many causes of signal distortions, including the ionosphere. To produce accurate astronomical images, calibration solutions are derived to mitigate these distortions as much as possible. These calibration solutions provide extremely precise measurements of ionospheric variations across the LOFAR network, enabling TIDs to be detected which may be inaccessible to more traditional techniques. Waves are detected by LOFAR under all observing conditions, with no clear dependence on solar or geomagnetic activity. The vast majority of the observed waves travel in the opposite direction to the climatological thermospheric winds, suggesting that they are caused by upward propagating atmospheric gravity waves which are filtered by the wind. Waves of different periods display slightly different propagation directions, with waves of shorter periods consistent with the winds at lower altitudes within the thermosphere (180 km for 10–15 min periods compared to 220 km for 20–27 min periods). This suggests that either the shorter period waves are being detected at lower altitudes or that they are simply more sensitive to the winds at lower altitudes. This indicates that observations made using LOFAR may enable the investigation of vertical coupling within the neutral atmosphere. The shortest period waves in the dataset (<∼10) display distinct characteristics, suggesting they may be from a distinct population such as previously reported disturbances in the plasmasphere. The short period waves are compared to previous observations using other radio telescopes, showing that plasmaspheric disturbances likely account for some of the shortest period waves (<∼5 min) but there are still a large number of waves at these periods which are of uncertain origin.

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LOFAR observations of asymmetric quasi-periodic scintillations in the mid-latitude ionosphere.

(2024)

Authors:

Gareth Dorrian, David R Themens, Toralf Renkwitz, Grzegorz Nykiel, Alan George Wood, Ben Boyde, Richard Andrew Fallows, Maaijke Mevius, Hannah Trigg

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The High Latitude Ionospheric Response to the Major May 2024 Geomagnetic Storm: A Synoptic View

Geophysical Research Letters American Geophysical Union (AGU) 51:19 (2024) e2024GL111677

Authors:

David R Themens, Sean Elvidge, Anthony McCaffrey, PT Jayachandran, Anthea Coster, Roger H Varney, Ivan Galkin, Lindsay V Goodwin, Chris Watson, Sophie Maguire, Andrew J Kavanagh, Shun‐Rong Zhang, Larisa Goncharenko, Asti Bhatt, Gareth Dorrian, Keith Groves, Alan G Wood, Ben Reid

Abstract:

Abstract The high latitude ionospheric evolution of the May 10‐11, 2024, geomagnetic storm is investigated in terms of Total Electron Content and contextualized with Incoherent Scatter Radar and ionosonde observations. Substantial plasma lifting is observed within the initial Storm Enhanced Density plume with ionospheric peak heights increasing by 150–300 km, reaching levels of up to 630 km. Scintillation is observed within the cusp during the initial expansion phase of the storm, spreading across the auroral oval thereafter. Patch transport into the polar cap produces broad regions of scintillation that are rapidly cleared from the region after a strong Interplanetary Magnetic Field reversal at 2230UT. Strong heating and composition changes result in the complete absence of the F2‐layer on the eleventh, suffocating high latitude convection from dense plasma necessary for Tongue of Ionization and patch formation, ultimately resulting in a suppression of polar cap scintillation on the eleventh.

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Dr Gareth Dorrian

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Radio Astronomy, the Earth’s Atmosphere and Geometric Optics: A Hands-On Activity for Secondary School Students

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Statistics of Small-Scale Ionospheric Waves in European Mid-Latitudes Observed Using LOFAR

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Abstract:

Statistics of travelling ionospheric disturbances observed using the LOFAR radio telescope

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Abstract:

LOFAR observations of asymmetric quasi-periodic scintillations in the mid-latitude ionosphere.

Authors:

The High Latitude Ionospheric Response to the Major May 2024 Geomagnetic Storm: A Synoptic View

Authors:

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Dr Gareth Dorrian

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Radio Astronomy, the Earth&#8217;s Atmosphere and Geometric Optics: A Hands-On Activity for Secondary School Students

Authors:

Abstract:

Statistics of Small-Scale Ionospheric Waves in European Mid-Latitudes Observed Using LOFAR

Authors:

Abstract:

Statistics of travelling ionospheric disturbances observed using the LOFAR radio telescope

Authors:

Abstract:

LOFAR observations of asymmetric quasi-periodic scintillations in the mid-latitude ionosphere.

Authors:

The High Latitude Ionospheric Response to the Major May 2024 Geomagnetic Storm: A Synoptic View

Authors:

Abstract:

Radio Astronomy, the Earth’s Atmosphere and Geometric Optics: A Hands-On Activity for Secondary School Students