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  • 1
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    Morphological aspects of the attenuation bands associated with Jovian hectometric radiation (2011)
    Wiley
    Details
    Publication Date: 2011-11-10
    Description: We study the frequency and time variations of Jovian hectometric emissions (HOM) recorded by the Radio and Plasma Wave Science (RPWS) experiment onboard the Cassini spacecraft during its Jupiter flyby. The capabilities of the RPWS experiment enable us to analyze the intensity extinction of HOM radiation, the so-called attenuation band. Using about 7 weeks of RPWS data obtained around the closest approach, a statistical analysis investigates the spectral variations of this phenomenon with respect to the spacecraft magnetic latitude and central meridian longitude. We show that the ‘trace’ of the attenuation band is usually not a full sinusoid as reported in previous studies and only parts of the curve are observed. Also, the intensity extinction can occur when the spacecraft is not in the planetary magnetic equator plane. This specific feature appears or vanishes when the observer (e.g., Cassini or Galileo spacecraft) is far from or close to the planet, respectively. The regular and systematic observations of the attenuation band suggest that the plasma medium at the origin of these features is steady and stable. The Io torus may be considered to be the most probable plasma medium where HOM emission is refracted through its raypath propagation. Furthermore, intensity extinction at frequencies higher than 3 MHz and up to 5 MHz implies the presence of particular electronic density irregularities in the Io torus. Volcanic activity, particularly in the northern hemisphere of the Io satellite, may be the source of such Io torus plasma irregularities.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    The non-convex shape of (234) Barbara, the first Barbarian (2015)
    Oxford University Press
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    Publication Date: 2015-03-13
    Description: Asteroid (234) Barbara is the prototype of a category of asteroids that has been shown to be extremely rich in refractory inclusions, the oldest material ever found in the Solar system. It exhibits several peculiar features, most notably its polarimetric behaviour. In recent years other objects sharing the same property (collectively known as ‘Barbarians’) have been discovered. Interferometric observations in the mid-infrared with the ESO VLTI (Very Large Telescope Interferometer) suggested that (234) Barbara might have a bi-lobated shape or even a large companion satellite. We use a large set of 57 optical light curves acquired between 1979 and 2014, together with the timings of two stellar occultations in 2009, to determine the rotation period, spin-vector coordinates, and 3-D shape of (234) Barbara, using two different shape reconstruction algorithms. By using the light curves combined to the results obtained from stellar occultations, we are able to show that the shape of (234) Barbara exhibits large concave areas. Possible links of the shape to the polarimetric properties and the object evolution are discussed. We also show that VLTI data can be modelled without the presence of a satellite.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 3
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    The importance of monopole antennas for dust observations: why Wind/WAVES does not detect nanodust (2014)
    Wiley
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    Publication Date: 2014-04-14
    Description: The charge released by impact ionization of fast dust grains impinging on spacecraft is at the basis of a well-known technique for dust detection by wave instruments. Since most of the impact charges are recollected by the spacecraft, monopole antennas generally detect a much greater signal than dipoles. This is illustrated by comparing dust signals in monopole and dipole mode on different spacecraft and environments. It explains the weak sensitivity of Wind /WAVES dipole antennas for dust detection, so that it is not surprising that this instrument did not detect the interplanetary nanodust discovered by STEREO/WAVES. We propose an interpretation of the Wind dust data, elsewhere discussed by Malaspina et al. [2014], which explains the observed pulse amplitude and polarity for interstellar dust impacts, as well as the non-detection of nanodust. This proposed mechanism might be the dominant dust detection mechanism by some wave instruments using dipole antennas.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Voyager planetary radio astronomy at neptune (1989)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1989-12-15
    Description: Detection of very intense short radio bursts from Neptune was possible as early as 30 days before closest approach and at least 22 days after closest approach. The bursts lay at frequencies in the range 100 to 1300 kilohertz, were narrowband and strongly polarized, and presumably originated in southern polar regions ofthe planet. Episodes of smooth emissions in the frequency range from 20 to 865 kilohertz were detected during an interval of at least 10 days around closest approach. The bursts and the smooth emissions can be described in terms of rotation in a period of 16.11 +/- 0.05 hours. The bursts came at regular intervals throughout the encounter, including episodes both before and after closest approach. The smooth emissions showed a half-cycle phase shift between the five episodes before and after closest approach. This experiment detected the foreshock of Neptune's magnetosphere and the impacts of dust at the times of ring-plane crossings and also near the time of closest approach. Finally, there is no evidence for Neptunian electrostatic discharges.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Warwick, J W -- Evans, D R -- Peltzer, G R -- Peltzer, R G -- Romig, J H -- Sawyer, C B -- Riddle, A C -- Schweitzer, A E -- Desch, M D -- Kaiser, M L -- Farrell, W M -- Carr, T D -- de Pater, I -- Staelin, D H -- Gulkis, S -- Poynter, R L -- Boischot, A -- Genova, F -- Leblanc, Y -- Lecacheux, A -- Pedersen, B M -- Zarka, P -- New York, N.Y. -- Science. 1989 Dec 15;246(4936):1498-501.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17756007" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
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    Ulysses radio and plasma wave observations in the jupiter environment (1992)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1992-09-11
    Description: The Unified Radio and Plasma Wave (URAP) experiment has produced new observations of the Jupiter environment, owing to the unique capabilities of the instrument and the traversal of high Jovian latitudes. Broad-band continuum radio emission from Jupiter and in situ plasma waves have proved valuable in delineating the magnetospheric boundaries. Simultaneous measurements of electric and magnetic wave fields have yielded new evidence of whistler-mode radiation within the magnetosphere. Observations of aurorallike hiss provided evidence of a Jovian cusp. The source direction and polarization capabilities of URAP have demonstrated that the outer region of the lo plasma torus supported at least five separate radio sources that reoccurred during successive rotations with a measurable corotation lag. Thermal noise measurements of the lo torus densities yielded values in the densest portion that are similar to models suggested on the basis of Voyager observations of 13 years ago. The URAP measurements also suggest complex beaming and polarization characteristics of Jovian radio components. In addition, a new class of kilometer-wavelength striated Jovian bursts has been observed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stone, R G -- Pedersen, B M -- Harvey, C C -- Canu, P -- Cornilleau-Wehrlin, N -- Desch, M D -- de Villedary, C -- Fainberg, J -- Farrell, W M -- Goetz, K -- Hess, R A -- Hoang, S -- Kaiser, M L -- Kellogg, P J -- Lecacheux, A -- Lin, N -- Macdowall, R J -- Manning, R -- Meetre, C A -- Meyer-Vernet, N -- Moncuquet, M -- Osherovich, V -- Reiner, M J -- Tekle, A -- Thiessen, J -- Zarka, P -- New York, N.Y. -- Science. 1992 Sep 11;257(5076):1524-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17776162" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
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    Radio and plasma wave observations at Saturn from Cassini's approach and first orbit (2004)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2004-12-18
    Description: We report data from the Cassini radio and plasma wave instrument during the approach and first orbit at Saturn. During the approach, radio emissions from Saturn showed that the radio rotation period is now 10 hours 45 minutes 45 +/- 36 seconds, about 6 minutes longer than measured by Voyager in 1980 to 1981. In addition, many intense impulsive radio signals were detected from Saturn lightning during the approach and first orbit. Some of these have been linked to storm systems observed by the Cassini imaging instrument. Within the magnetosphere, whistler-mode auroral hiss emissions were observed near the rings, suggesting that a strong electrodynamic interaction is occurring in or near the rings.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gurnett, D A -- Kurth, W S -- Hospodarsky, G B -- Persoon, A M -- Averkamp, T F -- Cecconi, B -- Lecacheux, A -- Zarka, P -- Canu, P -- Cornilleau-Wehrlin, N -- Galopeau, P -- Roux, A -- Harvey, C -- Louarn, P -- Bostrom, R -- Gustafsson, G -- Wahlund, J-E -- Desch, M D -- Farrell, W M -- Kaiser, M L -- Goetz, K -- Kellogg, P J -- Fischer, G -- Ladreiter, H-P -- Rucker, H -- Alleyne, H -- Pedersen, A -- New York, N.Y. -- Science. 2005 Feb 25;307(5713):1255-9. Epub 2004 Dec 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USA. donald-gurnett@uiowa.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15604362" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
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    Outburst of Jupiter's synchrotron radiation after the impact of comet Shoemaker-Levy 9 (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-06-30
    Description: Jupiter's nonthermal microwave emission, as measured by a global network of 11 radio telescopes, increased dramatically during the Shoemaker-Levy 9 impacts. The increase was wavelength-dependent, varying from approximately 10 percent at 70 to 90 centimeters to approximately 45 percent at 6 and 36 centimeters. The radio spectrum hardened (flattened toward shorter wavelengths) considerably during the week of impacts and continued to harden afterward. After the week of cometary impacts, the flux density began to subside at all wavelengths and was still declining 3 months later. Very Large Array and Australia Telescope images of the brightness distribution showed the enhancement to be localized in longitude and concentrated near the magnetic equator. The evidence therefore suggests that the increase in flux density was caused by a change in the resident particle population, for example, through an energization or spatial redistribution of the emitting particles.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉de Pater, I -- Heiles, C -- Wong, M -- Maddalena, R J -- Bird, M K -- Funke, O -- Neidhoefer, J -- Price, R M -- Kesteven, M -- Calabretta, M -- Klein, M J -- Gulkis, S -- Bolton, S J -- Foster, R S -- Sukumar, S -- Strom, R G -- LePoole, R S -- Spoelstra, T -- Robison, M -- Hunstead, R W -- Campbell-Wilson, D -- Ye, T -- Dulk, G -- Leblanc, Y -- Lecacheux, A -- New York, N.Y. -- Science. 1995 Jun 30;268(5219):1879-83.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Astronomy Department, University of California, Berkeley 94720, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11536723" target="_blank"〉PubMed〈/a〉
    Keywords: Astronomical Phenomena ; Astronomy ; Cosmic Dust ; *Electrons ; Elementary Particle Interactions ; *Jupiter ; *Meteoroids ; *Microwaves ; Spectrum Analysis
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
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    Planetary radio astronomy observations from voyager 1 near saturn (1981)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1981-04-10
    Description: The Voyager 1 planetary radio astronomy experiment detected two distinct kinds of radio emissions from Saturn. The first, Saturn kilometric radiation, is strongly polarized, bursty, tightly correlated with Saturn's rotation, and exhibits complex dynamic spectral features somewhat reminiscent of those in Jupiter's radio emission. It appears in radio frequencies below about 1.2 megahertz. The second kind of radio emission, Saturn electrostatic discharge, is unpolarized, extremely impulsive, loosely correlated with Saturn's rotation, and very broadband, appearing throughout the observing range of the experiment (20.4 kilohertz to 40.2 megahertz). Its sources appear to lie in the planetary rings.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Warwick, J W -- Pearce, J B -- Evans, D R -- Carr, T D -- Schauble, J J -- Alexander, J K -- Kaiser, M L -- Desch, M D -- Pedersen, M -- Lecacheux, A -- Daigne, G -- Boischot, A -- Barrow, C H -- New York, N.Y. -- Science. 1981 Apr 10;212(4491):239-43.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17783837" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
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    Planetary radio astronomy observations from voyager 2 near saturn (1982)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1982-01-29
    Description: Planetary radio astronomy measurements obtained by Voyager 2 near Saturn have added further evidence that Saturnian kilometric radiation is emitted by a strong dayside source at auroral latitudes in the northern hemisphere and by a weaker source at complementary latitudes in the southern hemisphere. These emissions are variable because of Saturn's rotation and, on longer time scales, probably because of influences of the solar wind and Dione. The electrostatic discharge bursts first discovered by Voyager 1 and attributed to emissions from the B ring were again observed with the same broadband spectral properties and an episodic recurrence period of about 10 hours, but their occurrence frequency was only about 30 percent of that detected by Voyager 1. While crossing the ring plane at a distance of 2.88 Saturn radii, the spacecraft detected an intense noise event extending to above 1 megahertz and lasting about 150 seconds. The event is interpreted to be a consequence of the impact, vaporization, and ionization of charged, micrometer-size G ring particles distributed over a vertical thickness of about 1500 kilometers.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Warwick, J W -- Evans, D R -- Romig, J H -- Alexander, J K -- Desch, M D -- Kaiser, M L -- Aubier, M -- Leblanc, Y -- Lecacheux, A -- Pedersen, B M -- New York, N.Y. -- Science. 1982 Jan 29;215(4532):582-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17771282" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
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    Voyager 2 radio observations of uranus (1986)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1986-07-04
    Description: Within distances to Uranus of about 6 x 10(6) kilometers (inbound) and 35 x 10(6) kilometers (outbound), the planetary radio astronomy experiment aboard Voyager 2 detected a wide variety of radio emissions. The emission was modulated in a period of 17.24 +/- 0.01 hours, which is identified as the rotation period of Uranus' magnetic field. Of the two poles where the axis of the off-center magnetic dipole (measured by the magnetometer experiment aboard Voyager 2) meets the planetary surface, the one closer to dipole center is now located on the nightside of the planet. The radio emission generally had maximum power and bandwidth when this pole was tipped toward the spacecraft. When the spacecraft entered the nightside hemisphere, which contains the stronger surface magnetic pole, the bandwidth increased dramatically and thereafter remained large. Dynamically evolving radio events of various kinds embedded in these emissions suggest a Uranian magnetosphere rich in magnetohydrodynamic phenomena.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Warwick, J W -- Evans, D R -- Romig, J H -- Sawyer, C B -- Desch, M D -- Kaiser, M L -- Alexander, J K -- Carr, T D -- Staelin, D H -- Gulkis, S -- Poynter, R L -- Aubier, M -- Boischot, A -- Leblanc, Y -- Lecacheux, A -- Pedersen, B M -- Zarka, P -- New York, N.Y. -- Science. 1986 Jul 4;233(4759):102-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17812898" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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