Dr Gareth Dorrian: Publications

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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Observations of High Definition Symmetric Quasi‐Periodic Scintillations in the Mid‐Latitude Ionosphere With LOFAR

Journal of Geophysical Research: Space Physics American Geophysical Union (AGU) 129:7 (2024) e2023JA032336

Authors:

H Trigg, G Dorrian, B Boyde, A Wood, RA Fallows, M Mevius

Abstract:

AbstractWe present broadband ionospheric scintillation observations of highly defined symmetric quasi‐periodic scintillations (QPS: Maruyama, 1991, https://doi.org/10.1029/91rs00357) caused by plasma structures in the mid‐latitude ionosphere using the LOw Frequency ARray (LOFAR: van Haarlem et al., 2013, https://doi.org/10.1051/0004‐6361/201220873). Two case studies are shown, one from 15 December 2016, and one from 30 January 2018, in which well‐defined main signal fades are observed to be bounded by secondary diffraction fringing. The ionospheric plasma structures effectively behave as a Fresnel obstacle, in which steep plasma gradients at the periphery result in a series of decreasing intensity interference fringes, while the center of the structures largely block the incoming radio signal altogether. In particular, the broadband observing capabilities of LOFAR permit us to see considerable frequency dependent behavior in the QPSs which, to our knowledge, is a new result. We extract some of the clearest examples of scintillation arcs reported in an ionospheric context, from delay‐Doppler spectral analysis of these two events. These arcs permit the extraction of propagation velocities for the plasma structures causing the QPSs ranging from 50 to 00 m s−1, depending on the assumed altitude. The spacing between the individual plasma structures ranges between 5 and 20 km. The periodicities of the main signal fades in each event and, in the case of the 2018 data, co‐temporal ionosonde data, suggest the propagation of the plasma structures causing the QPSs are in the E‐region. Each of the two events is accurately reproduced using a thin screen phase model. Individual signal fades and enhancements were modeled using small variations in total electron content (TEC) amplitudes of order 1 mTECu, demonstrating the sensitivity of LOFAR to very small fluctuations in ionospheric plasma density. To our knowledge these results are among the most detailed observations and modeling of QPSs in the literature.

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Dr Gareth Dorrian

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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

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:

Observations of High Definition Symmetric Quasi‐Periodic Scintillations in the Mid‐Latitude Ionosphere With LOFAR

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Dr Gareth Dorrian

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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:

Observations of High Definition Symmetric Quasi‐Periodic Scintillations in the Mid‐Latitude Ionosphere With LOFAR

Authors:

Abstract: