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  • 1
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    An interhemispheric comparison of GPS phase scintillation with auroral emission observed at the South Pole and from the DMSP satellite (2013)
    INGV
    Details
    Publication Date: 2020-12-03
    Description: The global positioning system (GPS) phase scintillation caused by highlatitude ionospheric irregularities during an intense high-speed stream (HSS) of the solar wind from April 29 to May 5, 2011, was observed using arrays of GPS ionospheric scintillation and total electron content monitors in the Arctic and Antarctica. The one-minute phase-scintillation index derived from the data sampled at 50 Hz was complemented by a proxy index (delta phase rate) obtained from 1-Hz GPS data. The scintillation occurrence coincided with the aurora borealis and aurora australis observed by an all-sky imager at the South Pole, and by special sensor ultraviolet scanning imagers on board satellites of the Defense Meteorological Satellites Program. The South Pole (SP) station is approximately conjugate with two Canadian High Arctic Ionospheric Network stations on Baffin Island, Canada, which provided the opportunity to study magnetic conjugacy of scintillation with support of riometers and magnetometers. The GPS ionospheric pierce points were mapped at their actual or conjugate locations, along with the auroral emission over the South Pole, assuming an altitude of 120 km. As the aurora brightened and/or drifted across the field of view of the all-sky imager, sequences of scintillation events were observed that indicated conjugate auroras as a locator of simultaneous or delayed bipolar scintillation events. In spite of the greater scintillation intensity in the auroral oval, where phase scintillation sometimes exceeded 1 radian during the auroral break-up and substorms, the percentage occurrence of moderate scintillation was highest in the cusp. Interhemispheric comparisons of bipolar scintillation maps show that the scintillation occurrence is significantly higher in the southern cusp and polar cap.
    Description: Published
    Description: R0216
    Description: 1.7. Osservazioni di alta e media atmosfera
    Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale
    Description: JCR Journal
    Description: open
    Keywords: Scintillations ; Solar-terrestrial interaction ; Space weather ; Solar variability and solar wind ; Magnetic storms ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 01. Atmosphere::01.02. Ionosphere::01.02.05. Wave propagation ; 01. Atmosphere::01.02. Ionosphere::01.02.06. Instruments and techniques ; 01. Atmosphere::01.02. Ionosphere::01.02.07. Scintillations ; 05. General::05.07. Space and Planetary sciences::05.07.02. Space weather
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Electronic Resource
    Electronic Resource
    Ionospheric troughs in Antarctica (1982)
    [s.l.] : Nature Publishing Group
    Nature 295 (1982), S. 307-308 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The AÏS2 uses radio waves in the frequency range 0.1-30 MHz for remote sounding of the ionosphere. It provides a complete vector description of the ionospheric echoes obtained from each transmitted pulse, giving considerable advantage over the ionosonde. This, together with powerful online ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/295307a0
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Cross-modal transfer in the chimpanzee (1976)
    [s.l.] : Nature Publishing Group
    Nature 259 (1976), S. 44-46 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We assessed cross-modal transfer in three male chimpanzees (Pan troglodytes verus) weighing 16-20 kg, using procedures which have been described in earlier reports on monkeys7"9. The sequence of training is shown in Table 1. After preliminary adaptation to making two-choice simultaneous ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/259044b0
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  • 4
    Electronic Resource
    Electronic Resource
    Satellite Experiments Simultaneous with Antarctic Measurements (SESAME) (1995)
    Springer
    Space science reviews 71 (1995), S. 705-742 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Satellite Experiments Simultaneous with Antarctic Measurements (SESAME) is one of the four ground-based programmes within the NASA/ISAS Global Geospace Science (GGS) mission, itself part of the International Solar-Terrestrial Physics (ISTP) programme. The scientific objectives of SESAME are carefully selected to make an invaluable contribution to the GGS mission by capitalising on the unique geophysical advantages of Antarctica for geospace research. These arise mainly from the large displacement of the geographic and geomagnetic poles. Specifically, SESAME is designed to study the ionospheric effects of merging at the magnetopause, reconnection in the geomagnetic tail and its relationship to substorms, mapping of significant geospace boundaries to ionospheric altitudes, plasma wave generation and propagation at high latitudes, and ionosphere-thermosphere interactions. The experimental programme is centred at Halley (76° S, 27° W) but also utilises automatic geophysical observatories located poleward of Halley. The suite of instruments provides an excellent image of the inner boundary of geospace and thus is complementary to the GGS spacecraft measurements. The data products that will be supplied askey parameters to the GGS experimenters on a routine basis are described. A brief review of previous results is presented, and some of the significant scientific questions to be addressed using the combination of ground-based and space-based observations are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00751348
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  • 5
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    Herschel-ATLAS: the connection between star formation and AGN activity in radio-loud and radio-quiet active galaxies (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-09
    Description: We examine the relationship between star formation and active galactic nuclei (AGN) activity by constructing matched samples of local (0 〈  z  〈 0.6) radio-loud and radio-quiet AGN in the Herschel -Astrophysical Terahertz Large Area Survey fields. Radio-loud AGN are classified as high-excitation and low-excitation radio galaxies using their emission lines and WISE 22-μm luminosity. AGN accretion and jet powers in these active galaxies are traced by [O iii ] emission-line and radio luminosity, respectively. Star formation rates (SFRs) and specific star formation rates (SSFRs) were derived using Herschel 250-μm luminosity and stellar mass measurements from the Sloan Digital Sky Survey–Max Planck Institute for Astrophysics-John Hopkins University catalogue. In the past, star formation studies of AGN have mostly focused on high-redshift sources to observe the thermal dust emission that peaks in the far-infrared, which limited the samples to powerful objects. However, with Herschel we can expand this to low redshifts. Our stacking analyses show that SFRs and SSFRs of both radio-loud and radio-quiet AGN increase with increasing AGN power but that radio-loud AGN tend to have lower SFR. Additionally, radio-quiet AGN are found to have approximately an order of magnitude higher SSFRs than radio-loud AGN for a given level of AGN power. The difference between the star formation properties of radio-loud and -quiet AGN is also seen in samples matched in stellar mass.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 6
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    The faint radio source population at 15.7 GHz - II. Multi-wavelength properties (2015)
    Oxford University Press
    Details
    Publication Date: 2015-09-27
    Description: A complete, flux density limited sample of 96 faint (〉0.5 mJy) radio sources is selected from the 10C survey at 15.7 GHz in the Lockman Hole. We have matched this sample to a range of multi-wavelength catalogues, including Spitzer Extragalactic Representative Volume Survey, Spitzer Wide-area Infrared Extragalactic survey, United Kingdom Infrared Telescope Infrared Deep Sky Survey and optical data; multi-wavelength counterparts are found for 80 of the 96 sources and spectroscopic redshifts are available for 24 sources. Photometric redshifts are estimated for the sources with multi-wavelength data available; the median redshift of the sample is 0.91 with an interquartile range of 0.84. Radio-to-optical ratios show that at least 94 per cent of the sample are radio loud, indicating that the 10C sample is dominated by radio galaxies. This is in contrast to samples selected at lower frequencies, where radio-quiet AGN and star-forming galaxies are present in significant numbers at these flux density levels. All six radio-quiet sources have rising radio spectra, suggesting that they are dominated by AGN emission. These results confirm the conclusions of Paper I that the faint, flat-spectrum sources which are found to dominate the 10C sample below ~1 mJy are the cores of radio galaxies. The properties of the 10C sample are compared to the Square Kilometre Array Design Studies Simulated Skies; a population of low-redshift star-forming galaxies predicted by the simulation is not found in the observed sample.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 7
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    Radio Galaxy Zoo: host galaxies and radio morphologies derived from visual inspection (2015)
    Oxford University Press
    Details
    Publication Date: 2015-09-27
    Description: We present results from the first 12 months of operation of Radio Galaxy Zoo, which upon completion will enable visual inspection of over 170 000 radio sources to determine the host galaxy of the radio emission and the radio morphology. Radio Galaxy Zoo uses 1.4 GHz radio images from both the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) and the Australia Telescope Large Area Survey (ATLAS) in combination with mid-infrared images at 3.4 μm from the Wide-field Infrared Survey Explorer ( WISE ) and at 3.6 μm from the Spitzer Space Telescope . We present the early analysis of the WISE mid-infrared colours of the host galaxies. For images in which there is 〉75 per cent consensus among the Radio Galaxy Zoo cross-identifications, the project participants are as effective as the science experts at identifying the host galaxies. The majority of the identified host galaxies reside in the mid-infrared colour space dominated by elliptical galaxies, quasi-stellar objects and luminous infrared radio galaxies. We also find a distinct population of Radio Galaxy Zoo host galaxies residing in a redder mid-infrared colour space consisting of star-forming galaxies and/or dust-enhanced non-star-forming galaxies consistent with a scenario of merger-driven active galactic nuclei (AGN) formation. The completion of the full Radio Galaxy Zoo project will measure the relative populations of these hosts as a function of radio morphology and power while providing an avenue for the identification of rare and extreme radio structures. Currently, we are investigating candidates for radio galaxies with extreme morphologies, such as giant radio galaxies, late-type host galaxies with extended radio emission and hybrid morphology radio sources.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 8
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    Optimizing commensality of radio continuum and spectral line observations in the era of the SKA (2016)
    Oxford University Press
    Details
    Publication Date: 2016-06-24
    Description: The substantial decrease in star formation density from z = 1 to the present day is curious given the relatively constant neutral gas density over the same epoch. Future radio astronomy facilities, including the Square Kilometre Array (SKA) and pathfinder telescopes, will provide pioneering measures of both the gas content of galaxies and star formation activity over cosmological time-scales. Here we investigate the commensalities between neutral atomic gas (H i ) and radio continuum observations, as well as the complementarity of the data products. We start with the proposed H i and continuum surveys to be undertaken with the SKA precursor telescope MeerKAT, and building on this, explore optimal combinations of survey area coverage and depth of proposed H i and continuum surveys to be undertaken with the SKA1-MID instrument. Intelligent adjustment of these observational parameters results in a tiered strategy that minimizes observation time while maximizing the value of the data set, both for H i and continuum science goals. We also find great complementarity between the H i and continuum data sets, with the spectral line H i data providing redshift measurements for gas-rich, star-forming galaxies with stellar masses M * ~ 10 9 M to z ~ 0.3, a factor of 3 lower in stellar mass than would be feasible to reach with large optical spectroscopic campaigns.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 9
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    Far beyond stacking: fully Bayesian constraints on sub-{mu}Jy radio source populations over the XMM-LSS-VIDEO field (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-30
    Description: Measuring radio source counts is critical for characterizing new extragalactic populations, brings a wealth of science within reach and will inform forecasts for SKA and its pathfinders. Yet there is currently great debate (and few measurements) about the behaviour of the 1.4-GHz counts in the μJy regime. One way to push the counts to these levels is via ‘stacking’, the covariance of a map with a catalogue at higher resolution and (often) a different wavelength. For the first time, we cast stacking in a fully Bayesian framework, applying it to (i) the Square Kilometre Array Design Study (SKADS) simulation and (ii) Very Large Array (VLA) data stacked at the positions of sources from the VISTA Infra-red Deep Extragalactic Observations (VIDEO) survey. In the former case, the algorithm recovers the counts correctly when applied to the catalogue, but is biased high when confusion comes into play. This needs to be accounted for in the analysis of data from any relatively low-resolution Square Kilometre Array (SKA) pathfinders. For the latter case, the observed radio source counts remain flat below the 5- level of 85 μJy as far as 40 μJy, then fall off earlier than the flux hinted at by the SKADS simulations and a recent P ( D ) analysis (which is the only other measurement from the literature at these flux-density levels, itself extrapolated in frequency). Division into galaxy type via spectral-energy distribution reveals that normal spiral galaxies dominate the counts at these fluxes.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 10
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    A deep/wide 1-2 GHz snapshot survey of SDSS Stripe 82 using the Karl G. Jansky Very Large Array in a compact hybrid configuration (2016)
    Oxford University Press
    Details
    Publication Date: 2016-06-30
    Description: We have used the Karl G. Jansky Very Large Array to image ~100 deg 2 of SDSS Stripe 82 at 1–2 GHz. The survey consists of 1026 snapshot observations of 2.5 min duration, using the hybrid CnB configuration. The survey has good sensitivity to diffuse, low surface brightness structures and extended radio emission, making it highly synergistic with existing 1.4 GHz radio observations of the region. The principal data products are continuum images, with 16  x  10 arcsec resolution, and a catalogue containing 11 782 point and Gaussian components resulting from fits to the thresholded Stokes-I brightness distribution, forming approximately 8948 unique radio sources. The typical effective 1 noise level is 88 μJy beam –1 . Spectral index estimates are included, as derived from the 1 GHz of instantaneous bandwidth. Astrometric and photometric accuracy are in excellent agreement with existing narrowband observations. A large-scale simulation is used to investigate clean bias, which we extend into the spectral domain. Clean bias remains an issue for snapshot surveys with the VLA, affecting our total intensity measurements at the ~1 level. Statistical spectral index measurements are in good agreement with existing measurements derived from matching separate surveys at two frequencies. At flux densities below ~35 the median in-band spectral index measurements begin to exhibit a bias towards flatness that is dependent on both flux density and the intrinsic spectral index. In-band spectral curvature measurements are likely to be unreliable for all but the very brightest components. Image products and catalogues are publicly available via an FTP server.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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