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1.
J. L. Bertaux E. Quémerais R. Lallement E. Kyrölä W. Schmidt T. Summanen J. P. Goutail M. Berthé J. Costa T. Holzer 《Solar physics》1997,175(2):737-770
After one year of almost flawless operation on board the SOHO spacecraft poised at L1 Lagrange point, we report the main features
of SWAN observations. SWAN is mainly dedicated to the monitoring of the latitude distribution of the solar wind by the Lα
method. Maps of sky Lα emissions were recorded througout the year. The region of maximum emission, located in the upwind hemisphere,
deviates strongly from the pattern that could be expected from a solar wind constant with latitude. It is divided into two
lobes by a depression aligned with the solar equatorial plane called the Lyα groove already noted in 1976 Prognoz data. The
north lobe is much brighter than the south lobe. These two characteristics can be explained qualitatively by an enhanced ionization
along the neutral sheet where the slow solar wind is concentrated, which results from the higher low-latitude solar wind mass
flux as measured by Ulysses. The groove is the direct imprint on the sky of the enhanced carving by the slow solar wind, at
this time of solar minimum, when the tilt angle of the neutral sheet is small. The question is still pending to predict what
will happen with the ascending phase of the solar cycle. Observations of comets are briefly mentioned, with the ability of
SWAN to monitor the H2O production of many comets. Operations of the instrument are briefly described, including some instrumental problems which
could be solved by software modifications sent to the instrument.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1004979605559 相似文献
2.
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
3.
R. Lallement 《Astronomische Nachrichten》2012,333(4):347-350
Charge‐transfer (CT) X‐ray emission may occur at interfaces between a partially neutral gas and gas possessing high ions, provided there is a relative motion between those two phases. The CTX surface brightness from distant objects must be taken into account if it is not far below other “classical” emission sources, especially the thermal emission from the hot phase. I discuss those conditions and potential spectroscopic or photometric diagnostics. I also mention potential indirect effects of the CT reactions by means of pickup ion production, acceleration and subsequent modification of interface and plasma properties (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
J. L. Bertaux E. Kyrölä E. Quémerais R. Pellinen R. Lallement W. Schmidt M. Berthé E. Dimarellis J. P. Goutail C. Taulemesse C. Bernard G. Leppelmeier T. Summanen H. Hannula H. Huomo V. Kehlä S. Korpela K. Leppälä E. Strömmer J. Torsti K. Viherkanto J. F. Hochedez G. Chretiennot R. Peyroux T. Holzer 《Solar physics》1995,162(1-2):403-439
On board the SOHO spacecraft poised at L1 Lagrange point, the SWAN instrument is mainly devoted to the measurement of large scale structures of the solar wind, and in particular the distribution with heliographic latitude of the solar wind mass flux. This is obtained from an intensity map of the sky Lyman emission, which reflects the shape of the ionization cavity carved in the flow of interstellar H atoms by the solar wind. The methodology, inversion procedure and related complications are described. The subject of latitude variation of the solar wind is shortly reviewed: earlier Lyman results from Prognoz in 1976 are confirmed by Ulysses. The importance of the actual value of the solar wind mass flux for the equation of dynamics in a polar coronal hole is stressed. The instrument is composed of one electronic unit commanding two identical Sensor Units, each of them allowing to map a full hemisphere with a resolution of 1°, thanks to a two-mirrors periscope system. The design is described in some details, and the rationale for choice between several variants are discussed. A hydrogen absorption cell is used to measure the shape of the interplanetary Lyman line and other Lyman emissions. Other types of observations are also discussed : the geocorona, comets (old and new), the solar corona, and a possible signature of the heliopause. The connexion with some other SOHO instruments, in particular LASCO, UVCS, SUMER, is briefly discussed. 相似文献
5.
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
6.
S. Sembay G. Branduardi‐Raymont J.P. Eastwood D.G. Sibeck A. Abbey P. Brown J.A. Carter C.M. Carr C. Forsyth D. Kataria S. Kemble S. Milan C.J. Owen A.M. Read L. Peacocke C.S. Arridge A.J. Coates M.R. Collier S.W.H. Cowley A.N. Fazakerley G. Fraser G.H. Jones R. Lallement M. Lester F.S. Porter T. Yeoman 《Astronomische Nachrichten》2012,333(4):388-392
AXIOM (Advanced X‐ray Imaging Of the Magnetosphere) is a concept mission which aims to explain how the Earth's magnetosphere responds to the changing impact of the solar wind using a unique method never attempted before; performing wide‐field soft X‐ray imaging and spectroscopy of the magnetosheath, magnetopause and bow shock at high spatial and temporal resolution. Global imaging of these regions is possible because of the solar wind charge exchange (SWCX) process which produces elevated soft X‐ray emission from the interaction of high charge‐state solar wind ions with primarily neutral hydrogen in the Earth's exosphere and near‐interplanetary space (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
7.
Charge‐transfer is the main process linking neutrals and charged particles in the interaction regions of neutral (or partly ionized) gas with a plasma. In this paper we illustrate the importance of charge‐transfer with respect to the dynamics and the structure of neutral gas‐plasma interfaces. We consider the following phenomena: (1) the heliospheric interface ‐ region where the solar wind plasma interacts with the partly‐ionized local interstellar medium (LISM) and (2) neutral interstellar clouds embedded in a hot, tenuous plasma such as the million degree gas that fills the so‐called “Local Bubble”. In (1), we discuss several effects in the outer heliosphere caused by charge exchange of interstellar neutral atoms and plasma protons. In (2) we describe the role of charge exchange in the formation of a transition region between the cloud and the surrounding plasma based on a two‐component model of the cloud‐plasma interaction. In the model the cloud consists of relatively cold and dense atomic hydrogen gas, surrounded by hot, low density, fully ionized plasma. We discuss the structure of the cloud‐plasma interface and the effect of charge exchange on the lifetime of interstellar clouds. Charge transfer between neutral atoms and minor ions in the plasma produces X‐ray emission. Assuming standard abundances of minor ions in the hot gas surrounding the cold interstellar cloud, we estimate the X‐ray emissivity consecutive to the charge transfer reactions. Our model shows that the charge‐transfer X‐ray emission from the neutral cloud‐plasma interface may be comparable to the diffuse thermal X‐ray emission from the million degree gas cavity itself (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
M. A. Barstow D. D. Boyce J. K. Barstow A. E. Forbes B. Y. Welsh R. Lallement 《Astrophysics and Space Science》2009,320(1-3):91-95
We report preliminary results of a search for O VI absorption in the spectra of ～100 hot DA white dwarfs observed by the FUSE satellite. We have carried out a detailed analysis of the radial velocities of interstellar and (where present) stellar absorption lines for the entire sample of stars. In many cases, the velocity differences between the interstellar and photospheric components are below the resolution of the FUSE spectrographs. However, in a significant number of cases the interstellar and photospheric contributions can be separated. In the majority of stars where we find O VI absorption lines, the material is clearly associated with the stellar photosphere and not the interstellar medium. There are a small number of lines-of-sight where the gas is interstellar in nature but the stars are located beyond the boundaries of the local cavity. 相似文献
9.
10.
R. Lallement 《Astrophysics and Space Science》2001,277(1-2):205-217
In this paper I will use recent results about the heliosphere and the so-called `H walls' around nearby star ‘asteropauses’
(the equivalent of the heliopause for other stars) to show new connections between heliospheric physics and other fields in
space physics.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献