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Rosine Lallement Bertaux Jean-Loup Karöly Szegö Szilvia Nemeth 《Earth, Moon, and Planets》2002,90(1-4):67-76
For a few months around perihelion, thecentral part of the Hale–Bopp hydrogencloud has been optically thick to thesolar Lyα
radiation, and hassignificantly reduced the solar flux availablefor the resonance glow of interstellarhydrogen beyond the
comet. This shadowing effecton the interstellar gas is the first everobserved comet shadow. It is modeled andcompared with
SWAN observations. Shadowmodelling will help to constrain the cometwater production and radiative transfer effectsin the interstellar
ionisation cavity. 相似文献
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Bertaux Jean-Loup QuÉmerais Eric Lallement Rosine KyrÖlÄ Erkki Summanen Tuula 《Solar physics》1997,170(2):365-370
In a recently published paper, Scherer and Fahr (1995) claimed that the departures of sky L emission measured by Prognoz 5 and 6 from an optically thin model can be attributed entirely to deficiencies of the optically thin approximation, and are not due to variations of solar wind ionization rate with latitude, as advocated since many years by our research group. They base their claim on the result of their new sophisticated model of L radiation transport.It is shown here that their new model, in the simple case of isotropic solar wind, predicts a distribution of intensity in a simple geometry which is completely contradicted by the observations: they find a minimum of intensity near the upwind direction, where a maximum has been observed consistently by all L instruments. Therefore, their conclusion based on an erroneous model must be rejected. 相似文献
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AXIOM: advanced X-ray imaging of the magnetosphere 总被引:1,自引:0,他引:1
Graziella Branduardi-Raymont Steve F. Sembay Jonathan P. Eastwood David G. Sibeck Tony A. Abbey Patrick Brown Jenny A. Carter Chris M. Carr Colin Forsyth Dhiren Kataria Steve Kemble Steve E. Milan Chris J. Owen Lisa Peacocke Andy M. Read Andrew J. Coates Michael R. Collier Stan W. H. Cowley Andrew N. Fazakerley George W. Fraser Geraint H. Jones Rosine Lallement Mark Lester F. Scott Porter Tim K. Yeoman 《Experimental Astronomy》2012,33(2-3):403-443
Planetary plasma and magnetic field environments can be studied in two complementary ways—by in situ measurements, or by remote sensing. While the former provide precise information about plasma behaviour, instabilities and dynamics on local scales, the latter offers the global view necessary to understand the overall interaction of the magnetospheric plasma with the solar wind. Some parts of the Earth’s magnetosphere have been remotely sensed, but the majority remains unexplored by this type of measurements. Here we propose a novel and more elegant approach employing remote X-ray imaging techniques, which are now possible thanks to the relatively recent discovery of solar wind charge exchange X-ray emissions in the vicinity of the Earth’s magnetosphere. In this article we describe how an appropriately designed and located X-ray telescope, supported by simultaneous in situ measurements of the solar wind, can be used to image the dayside magnetosphere, magnetosheath and bow shock, with a temporal and spatial resolution sufficient to address several key outstanding questions concerning how the solar wind interacts with the Earth’s magnetosphere on a global level. Global images of the dayside magnetospheric boundaries require vantage points well outside the magnetosphere. Our studies have led us to propose ‘AXIOM: Advanced X-ray Imaging of the Magnetosphere’, a concept mission using a Vega launcher with a LISA Pathfinder-type Propulsion Module to place the spacecraft in a Lissajous orbit around the Earth–Moon L1 point. The model payload consists of an X-ray Wide Field Imager, capable of both imaging and spectroscopy, and an in situ plasma and magnetic field measurement package. This package comprises a Proton-Alpha Sensor, designed to measure the bulk properties of the solar wind, an Ion Composition Analyser, to characterise the minor ion populations in the solar wind that cause charge exchange emission, and a Magnetometer, designed to measure the strength and direction of the solar wind magnetic field. We also show simulations that demonstrate how the proposed X-ray telescope design is capable of imaging the predicted emission from the dayside magnetosphere with the sensitivity and cadence required to achieve the science goals of the mission. 相似文献
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Vladislav V. Izmodenov Yury G. Malama Alexandr P. Kalinin Mike Gruntman Rosine Lallement Irina P. Rodionova 《Astrophysics and Space Science》2000,274(1-2):71-76
Williams et al. (1997) have suggested that a population of hot hydrogen atoms is created in the heliosphere through elastic H-H collisions
between energetic `solar' atoms (neutralized solar wind) and interstellar atoms. They used a BGK-like approximation (Bhatnagar
et al., 1954) for the Boltzmann collision term and the collision cross sections suggested by Dalgarno (1960). We show that both
assumptions result in a significant overestimation of the the H-H collision effect. On the basis of calculated momentum transfer
cross-sections for elastic H-H collisions, we argue that elastic H-H and H-p collisions cannot produce hot H atoms in the
heliosphere.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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