Gareth Dorrian

Gareth Dorrian
University of Birmingham · School of Electronic, Electrical and Computer Engineering

About

33
Publications
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348
Citations

Publications

Publications (33)
Article
Full-text available
Polar holes were observed in the high-latitude ionosphere during a series of multi-instrument case studies close to the Northern Hemisphere winter solstice in 2014 and 2015. These holes were observed during geomagnetically quiet conditions and under a range of solar activities using the European Incoherent Scatter (EISCAT) Svalbard Radar (ESR) and...
Preprint
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This paper presents the results from one of the first observations of ionospheric scintillation taken using the Low-Frequency Array (LOFAR). The observation was of the strong natural radio source Cas A, taken overnight on 18-19 August 2013, and exhibited moderately strong scattering effects in dynamic spectra of intensity received across an observi...
Article
Full-text available
This paper presents the results from one of the first observations of ionospheric scintillation taken 78 using the Low-Frequency Array (LOFAR). The observation was of the strong natural radio source Cassiopeia A, taken overnight on 18-19 August 2013, and exhibited moderately strong scattering effects in dynamic spectra of intensity received across...
Article
Full-text available
Polar holes were observed in the high-latitude ionosphere during a series of multi-instrument case studies close to the northern hemisphere winter solstice in 2014 and 2015. These holes were observed during geomagnetically quiet conditions and under a range of solar activities using the European Incoherent Scatter Scientific Association (EISCAT) Sv...
Article
Full-text available
Plain Language Summary The upper atmosphere of the Earth is a mixture of partially ionized plasma (the ionosphere) and neutral gases (the thermosphere). The plasma is comprised of charged particles which are subject to electromagnetic forces, whereas the neutral thermosphere is not. These two populations are the coupled ionosphere‐thermosphere. Pla...
Article
Full-text available
We study the influence of the large-scale interplanetary magnetic field configuration on the solar energetic particles (SEPs) as detected at different satellites near Earth and on the correlation of their peak intensities with the parent solar activity. We selected SEP events associated with X- and M-class flares at western longitudes, in order to...
Article
Full-text available
We use dual-site radio observations of interplanetary scintillation (IPS) with extremely long baselines (ELB) to examine meridional flow characteristics of the ambient fast solar wind at plane-of-sky heliocentric distances of 24-85 solar radii (R\odot). Our results demonstrate an equatorwards deviation of 3-4{\deg} in the bulk fast solar wind flow...
Article
Shocks driven by fast coronal mass ejections (CMEs) are the dominant particle accelerators in large, “gradual” solar energetic particle (SEP) events. In these events, the event-integrated value of the iron-to-oxygen ratio (Fe/O) is typically ∼ 0.1, at least at energies of a few MeV/nucleon. However, at the start of some gradual events, when intensi...
Article
Full-text available
Occasionally, large solar energetic particle (SEP) events occur inside magnetic clouds (MCs). In this work, the onset time analysis, the peak intensity analysis, and the decay phase analysis of SEPs are used to investigate two large SEP events inside MCs: the 1998 May 2 and 2002 April 21 events. The onset time analysis of non-relativistic electrons...
Article
Full-text available
Stereoscopic white-light imaging of a large portion of the inner heliosphere has been used to track interplanetary coronal mass ejections. At large elongations from the Sun, the white-light brightness depends on both the local electron density and the efficiency of the Thomson-scattering process. To quantify the effects of the Thomson-scattering ge...
Article
Basic research on Space Weather carried out at the Institute of Astronomy and Astrophysics of the National Observatory of Athens within the framework of COMESEP, a collaborative project funded by the Seventh Framework Programme of the European Union is presented in this work. We carry out the first detailed examination and comparison of elemental s...
Article
Full-text available
A number of recent investigations have revealed that transverse waves are ubiquitous in the solar chromosphere. The vast majority of these have been reported in limb spicules and active region fibrils. We investigate long-lived, quiet Sun, on-disk features such as chromospheric mottles (jet-like features located at the boundaries of supergranular c...
Article
Analysis at high time resolution of radio scintillation observations made using the EISCAT facility of the slow solar wind during late April and early May 2007 suggested the presence of a considerable degree of small- and medium-scale structure, characterised by intervals of rapid field rotation. This hypothesis was supported by the large number of...
Article
Recent coordinated observations of interplanetary scintillation (IPS) and stereoscopic heliospheric imagers (HIs) are significant to continuously track the propagation and evolution of solar eruptions throughout interplanetary space. In order to obtain a better understanding of the observational signatures in these two remote-sensing techniques, th...
Article
This paper reports on the first combination of results from in-situ plasma measurements at Venus, using data from Venus Express, and remote sensing data from observations of interplanetary scintillation (IPS). In so doing, we demonstrate the value of combining remote sensing and in-situ techniques for the purpose of investigating interaction betwee...
Article
Full-text available
We discuss the detection and evolution of a complex series of transient and quasi-static solar-wind structures in the days following the well-known comet 2P/Encke tail disconnection event in April 2007. The evolution of transient solar-wind structures ranging in size from <105 km to >106 km was characterised using one-minute time resolution observa...
Article
Full-text available
The European Incoherent SCATter (EISCAT) radar has been used for remote-sensing observations of interplanetary scintillation (IPS) for a quarter of a century. During the April/May 2007 observing campaign, a large number of observations of IPS using EISCAT took place to give a reasonable spatial and temporal coverage of solar wind velocity structure...
Article
Interplanetary scintillation (IPS) observations provide views of the solar wind at all heliographic latitudes from near 1 A.U. down to fields of view covered by coronagraphs. These observations can be used to study the propagation of the solar wind and solar transients out into interplanetary space, and also measure the inner-heliospheric response...
Article
Interaction between interplanetary coronal mass ejections (ICMEs) and the background solar wind plays an important role in determining the velocity and structure of ICMEs at 1 AU. Interaction between ICMES can also significantly modify their structure, and recent studies suggest that a significant proportion of large geomagnetic storms are associat...
Article
Full-text available
Imaging of the heliosphere is a burgeoning area of research. As a result, it is awash with new results, using novel applications, and is demonstrating great potential for future research in a wide range of topical areas. The STEREO (Solar TErrestrial RElations Observatory) Heliospheric Imager (HI) instruments are at the heart of this new developmen...
Article
In her Lateral Thoughts article on the attitudes and priorities of Generations X and Y (February p52), Averil Macdonald asks "What did sociologists ever do for us?". After reading some of her arguments, we wonder if the answer is "they conduct social experiments by printing provocative articles and then observing the reaction". While we PhD-student...
Article
We present results from a co-ordinated study of solar wind structure in the inner helisphere during May 2007, combining results from radio measurements of interplanetary scintillation (IPS), STEREO HI imaging of interplanetary structures and in-situ measurements from the ASPERA instrument on Venus Express. The ASPERA results revealed periodic distu...
Article
The heliospheric imagers (HI) on the STEREO A and B spacecraft are now providing the first continuous, detailed images of structures in the interplanetary solar wind. When combined with simultaneous radio measurements of interplanetary scintillation (IPS), STEREO images allow the structure of the solar wind to be studied with much greater certainty...
Article
We present results from simultaneous Interplanetary Scintillation (IPS) and STEREO Heliospheric Imager (HI) observations of coronal mass ejections in the inner heliosphere. The combination of IPS and HI is an extremely powerful one, with HI providing the global context for interpreting the high-resolution observations from IPS. This makes it possib...
Article
This thesis discusses new observations made of large scale solar wind structure during solar minimum conditions. The phenomena of interplanetary radio scintillation (IPS) is exploited and used in conjunction with white light observations from the Heliospheric Imager instruments on the STEREO spacecraft. Methodologies for combining the two technique...
Article
Full-text available
We describe simultaneous Interplanetary Scintillation (IPS) and STEREO Heliospheric Imager (HI) observations of a coronal mass ejection (CME) on 16 May 2007. Strong CME signatures were present throughout the IPS observation. The IPS raypath lay within the field-of-view of HI-1 on STEREO-A and comparison of the observations shows that the IPS measur...
Article
Full-text available
Long-baseline observations of interplanetary scintillation (IPS) provide a unique source of information on solar wind speed and meridional direction across the inner regions of the solar system. We report the results of a series of coordinated IPS observations of an Earth-directed CME. A significant development in the interpretation of these data i...
Article
Full-text available
The antennas of EISCAT have been used for interplanetary scintillation (IPS) studies of the solar wind for many years. The main science found from these studies is obtained through the cross-correlation of signals from antennas having the longest baseline, providing more accurate information on the different solar wind streams which may be present...
Article
Full-text available
Improvements to two of the radio telescopes of European Incoherent SCATter radar (EISCAT) allow measurements of Interplanetary Scintillation (IPS) at 1.4 GHz, and this has prompted two major developments in studies of IPS. Simultaneous observations between EISCAT and MERLIN allow baselines of up to 2000 km, significantly improving velocity resoluti...
Article
Ground-based measurements of interplanetary scintillation (IPS) have been used to study the solar wind for many years, but interpretation of the results has always been rendered more difficult by uncertainty about the electron density distribution along the extended line-of-sight from radio source to antenna. This has been particularly marked in th...
Article
The technique of interplanetary scintillation (IPS) can be used to probe interplanetary space between the Sun and Earth most-commonly in terms of speed and also by using the scintillation-level (g-level) as a proxy for density. We combine the large spatial-scale 3D tomographic techniques previously only applied to IPS data from the Solar Terrestria...

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