1207 research outputs found
Sort by
The "SPectrogram Analysis and Cataloguing Environment"(SPACE) Labelling Tool
Full text linkThe SPectrogram Analysis and Cataloguing Environment (SPACE) tool is an interactive python tool designed to label radio emission features of interest in a time-frequency map (called "dynamic spectrum"). The program uses Matplotlib’s Polygon Selector widget to allow a user to select and edit an undefined number of vertices on top of the dynamic spectrum before closing the shape (polygon). Multiple polygons may be drawn on any spectrum, and the feature name along with the coordinates for each polygon vertex are saved into a ".json file as per the "Time-Frequency Catalogue" (TFCat) format along with other data such as the feature id, observer name, and data units. This paper describes the first official stable release (version 2.0) of the tool
Comparing Jupiter’s Equatorial X‐Ray Emissions With Solar X‐Ray Flux Over 19 Years of the Chandra Mission
Full text linkWe present a statistical study of Jupiter’s disk X-ray emissions using 19 years of Chandra X-Ray Observatory (CXO) observations. Previous work has suggested that these emissions are consistent with solar X-rays elastically scattered from Jupiter’s upper atmosphere. We showcase a new pulse invariant (PI) filtering method that minimizes instrumental effects which may produce unphysical trends in photon counts across the nearly two-decade span of the observations. We compare the CXO results with solar X-ray flux data from the Geostationary Operational Environmental Satellites X-ray Sensor for the wavelength band 1–8 Å (long channel), to quantify the correlation between solar activity and Jovian disk counts. We find a statistically significant Pearson’s Correlation Coefficient of 0.9, which confirms that emitted Jovian disk X-rays are predominantly governed by solar activity. We also utilize the high spatial resolution of the High Resolution Camera Instrument on-board the CXO to map the disk photons to their positions on Jupiter’s surface. Voronoi tessellation diagrams were constructed with the Juno Reference Model through Perijove 9 internal field model overlaid to identify any spatial preference of equatorial photons. After accounting for area and scattering across the curved surface of the planet, we find a preference of Jovian disk emission at 2–3.5 Gauss surface magnetic field strength. This suggests that a portion of the disk X-rays may be linked to processes other than solar scattering: the spatial preference associated with magnetic field strength may imply increased precipitation from the radiation belts, as previously postulated
Across and along-strike crustal structure variations of the western Afar margin and adjacent plateau: Insights from receiver functions analysis
Full text linkWe used teleseismic receiver function analysis to image the crustal structure beneath 24 broadband seismic
stations densely deployed along two profiles traversing different structural units across the western Afar margin.
Our high-resolution receiver function results image pronounced spatial variations in the crustal structure along
the profiles and provide improved insights to understand how strain is partitioned in the crust during rifting.
Beneath the western plateau next to northern Afar, the crust is likely felsic-to-intermediate in composition
(average Vp/Vs 1.74), with a step like thinning of the crust from an average of 38 km beneath the western
plateau to an average of 22 km beneath the marginal graben. Consistently thicker crust is observed beneath the
southern profile (central Afar), showing four distinct regions of uniform crustal thickness: 1) an average crustal
thickness of 42 km beneath the western plateau; 2) 34 km beneath the foothills area; 3) 28 km beneath the
marginal graben and the wide extensional basin and 4) 21 km beneath the central rift axis. We use crustal
thickness results to estimate a stretching factor β of 2.2 and 2.7 for central Afar and northern Afar respectively.
Our estimated values are lower than β > 3.0 predicted from plate reconstructions, and we interpret that the
variations are best explained by 2–5 km magmatic addition into the crust. The crustal composition beneath the
southern profile is more complex with elevated Vp/Vs ratios ranging between 1.79 and 1.85 beneath the western
plateau and marginal graben. This is consistent with a greater mafic component and best explained by crust
altered by intrusions due to significant pre and syn-rift magmatic activity. Abnormally high Vp/Vs ratios of more
than 1.90 are observed beneath the axial rift zone of central Afar, which most likely suggests the localization of
partial melt within the crust
An electric circuit model of the Earth’s polar electrojets and field-aligned currents for the estimation of magnetospheric magnetic field from along-track Swarm magnetic data
No full textThis study deals with the analysis of Swarm vector magnetic data in order to create a circuit model of electric currents flowing in the Earth’s polar ionosphere and the inner magnetosphere. The model is composed of a system of two-dimensional electric currents representing the magnetic fields of three-dimensional ionospheric polar electrojets (PEJs), the field-aligned currents (FACs), magnetospheric ring currents (MRCs) and magnetospherically induced electric currents inside the Earth (MICs) for each Swarm track. The aim of this paper is to model PEJ and FAC magnetic fields in terms of electric currents on a track-by-track base, subtract those magnetic fields from along-track Swarm magnetic data and estimate the magnetospheric magnetic field (MMF) in discrete time bins. The proposed method is primarily intended to apply to Swarm signals recorded during magnetic storms. The electric circuit model is set up in three steps. After subtracting the main, lithospheric, Sq ionospheric and oceanic tidal magnetic fields from along-track Swarm magnetic signals, the residuals are grouped in 1-h time bins and adjusted by the magnetic field of a two-circular loop model of MRCs and MICs represented by 3×2 parameters of the electric circular loops in the magnetosphere and the Earth. The adjustment is carried out for the X and Z magnetic field components only because the Y component contains a large signal due to FACs. In the second step, the modelled MRC–MIC magnetic field is removed from the original residuals and the reduced residuals are adjusted by the magnetic field of a system of two-dimensional electric circuits in the polar ionosphere and FACs. The circuit model is set up according to known geometry of PEJs and FACs. In the final step, the modelled magnetic fields of PEJs and FACs are subtracted from the original residuals and all three magnetic field components are adjusted by the MRC–MIC model, named MMC, in a similar way as in the first step. Reliability of the approach is demonstrated by the scatter plots of model MMC showing a significantly better agreement with Swarm magnetic field residuals than the existing MMFs
Bibliography of Irish Palaeography and Manuscript Studies, c. 1000-1650
Full text linkThis provides a reference tool for those working on Irish language manuscripts produced in Ireland between 1000 to 1650. The first section provides references to general works on Latin palaeography and codicology which will be of reference to those studying Irish manuscripts. The second section lists publications on Irish palaeography and manuscript studies mainly for manuscripts dated to between 1000 and 1650
THE RAFTA PROJECT: RESOLUTION ANALYSES FOR FREQUENCY- AND TIME-DOMAIN AIRBORNE ELECTROMAGNETIC DATA OF THE IRISH TELLUS PROGRAMME
Full text linkThe Tellus programme, operated by Geological Survey Ireland, is a national programme gathering
geochemical and airborne geophysical data across Ireland. As part of the geophysics programme, time-
domain electromagnetic (TDEM) data were measured in one survey block in 2014 and frequency-domain
electromagnetic (FDEM) data have been acquired in other data blocks since 2011 (Figure 1). The subsurface
resolution capabilities of both datasets are currently poorly understood. Project RAFTA will examine the
resolution capabilities of both the frequency-domain and time-domain data and will consider all aspects of
the data, including flight height, system noise and anthropogenic noise, which affect the resolution. The
resistivity models and model resolutions derived from recorded data will be tested against other constraints
where available that will include borehole logs, wireline resistivity logs and ERT sections, where possible at
test locations of interest in groundwater, bedrock mapping and Quaternary mapping. Model resolution will
also be assessed using synthetic data examples for a wide range of subsurface geological structures. The
maximum depth of investigation provided by these data are well suited for investigation of, e.g., overburden
thickness; nature of overburden material, including Quaternary deposits; depth to bedrock; bedrock
lithology
Method to observe Jupiter’s radio emissions at high resolution using multiple LOFAR stations: a first case study of the Io-decametric emission using the Irish IE613, French FR606, and German DE604 stations
Full text linkThe Low Frequency Array (LOFAR) is an international radio telescope array, consisting of 38 stations in the Netherlands and 14 international stations spread over Europe. Here, we present an observation method to study the Jovian decametric radio emissions from several LOFAR stations (here Birr Castle in Ireland, Nançay in France, and Postdam in Germany), at high temporal and spectral resolution. This method is based on prediction tools, such as radio emission simulations and probability maps, and data processing. We report an observation of Io-induced decametric emission from 2021 June, and a first case study of the substructures that compose the macroscopic emissions (called millisecond bursts). The study of these bursts makes it possible to determine the electron populations at the origin of these emissions. We then present several possible future avenues for study based on these observations. The methodology and study perspectives described in this paper can be applied to new observations of Jovian radio emissions induced by Io, but also by Ganymede or Europa, or Jovian auroral radio emissions
