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971.
G. Tobie B. Giese T. A. Hurford R. M. Lopes F. Nimmo F. Postberg K. D. Retherford J. Schmidt J. R. Spencer T. Tokano E. P. Turtle 《Space Science Reviews》2010,153(1-4):375-410
The surface morphology of icy moons is affected by several processes implicating exchanges between their subsurfaces and atmospheres (if any). The possible exchange of material between the subsurface and the surface is mainly determined by the mechanical properties of the lithosphere, which isolates the deep, warm and ductile ice material from the cold surface conditions. Exchanges through this layer occur only if it is sufficiently thin and/or if it is fractured owing to tectonic stresses, melt intrusion or impact cratering. If such conditions are met, cryomagma can be released, erupting fresh volatile-rich materials onto the surface. For a very few icy moons (Titan, Triton, Enceladus), the emission of gas associated with cryovolcanic activity is sufficiently large to generate an atmosphere, either long-lived or transient. For those moons, atmosphere-driven processes such as cryovolcanic plume deposition, phase transitions of condensable materials and wind interactions continuously re-shape their surfaces, and are able to transport cryovolcanically generated materials on a global scale. In this chapter, we discuss the physics of these different exchange processes and how they affect the evolution of the satellites’ surfaces. 相似文献
972.
973.
R.M. Gunasingha A.R. Fazely J.H. Adams Jr. H.S. Ahn G.L. Bashindzhagyan K.E. Batkov J. Chang M. Christl O. Ganel T.G. Guzik J. Isbert K.C. Kim E.N. Kouznetsov M.I. Panasyuk A.D. Panov W.K.H. Schmidt E.S. Seo N.V. Sokolskaya J.W. Watts J.P. Wefel J. Wu V.I. Zatsepin Z.W. Lin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
We have performed a detailed Monte-Carlo (MC) simulation for the Advanced Thin Ionization Calorimeter (ATIC) detector using the MC code FLUKA-2005 which is capable of simulating particles up to 10 PeV. The ATIC detector has completed two successful balloon flights from McMurdo, Antarctica lasting a total of more than 35 days. ATIC is designed as a multiple, long duration balloon flight, investigation of the cosmic ray spectra from below 50 GeV to near 100 TeV total energy; using a fully active Bismuth Germanate (BGO) calorimeter. It is equipped with a large mosaic of silicon detector pixels capable of charge identification, and, for particle tracking, three projective layers of x–y scintillator hodoscopes, located above, in the middle and below a 0.75 nuclear interaction length graphite target. Our simulations are part of an analysis package of both nuclear (A) and energy dependences for different nuclei interacting in the ATIC detector. The MC simulates the response of different components of the detector such as the Si-matrix, the scintillator hodoscopes and the BGO calorimeter to various nuclei. We present comparisons of the FLUKA-2005 MC calculations with GEANT calculations and with the ATIC CERN data. 相似文献
974.
To resolve interference problems between fixed-satellite and terrestrial radio relay services and expand coordination areas between the two services, theoretical and experimental studies were carried out. Theoretical D/U values calculation formulas between the two systems were derived, interference data from 4 GHz and 11 GHz band terrestrial radio-relay systems were obtained by a measuring system mounted on a vehicle. By comparing those results, it becomes clear that the ensemble interference reduction factors for 4 GHz and 11 GHz bands are around 20 dB, which is mixed values of attenuation and reflection from big buildings in urban areas 相似文献
975.
Zahirniak D.R. Sharpin D.L. Fields T.W. 《IEEE transactions on aerospace and electronic systems》1998,34(1):137-152
An approach is presented to realizing a digital channelized receiver for signal intercept applications that provides a hardware efficient implementation of a uniform filter bank in which the number of filters K is greater than the decimation factor M. The proposed architecture allows simple channel arbitration logic to be used and provides reliable instantaneous frequency measurements, even in adjacent channel crossover regions. In the proposed implementation of the filter bank, K is related to M by K=FM where F is an integer. It is shown that the optimum selection of F allows the instantaneous frequency measurement to be made in the channel crossover region and the arbitration function to be based solely on the instantaneous frequency measurement. The development of a filter bank structure which combines the flexibility of the short-time Fourier transform (STFT) with the implementation efficiency of the polyphase filter bank decomposition, meeting these requirements and leading to a hardware-efficient implementation, is presented 相似文献
976.
Recent papers have suggested that the slow solar wind is a super-position of material which is released by reconnection from
large coronal loops. This reconnection process is driven by large-scale motions of solar magnetic flux driven by the non-radial
expansion of the solar wind from the differentially rotating photosphere into more rigidly rotating coronal holes.
The elemental composition of the slow solar wind material is observed to be fractionated and more variable than the fast solar
wind from coronal holes. Recently, it has also been reported that fractionation also occurs in 3He/4He. This may be interpreted
in the frame-work of an existing model for fractionation on large coronal loops in which wave-particle interactions preferentially
heat ions thereby modifying their scale-heights.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
977.
K.T. Lee T.L. Wilson 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
We report on the results of a continuing study of the photon luminescence of the Moon induced by Galactic Cosmic Rays (GCRs) and space radiation from the Sun, using the Monte Carlo program FLUKA. Understanding the space radiation environment is critical to future exploration of the Moon, and this includes photons. The model of the lunar surface is taken to be the chemical composition of soils found at various landing sites during the Apollo and Luna programs, averaged over all such sites to define a generic regolith for the present analysis. This surface model then becomes the target that is bombarded by Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs) or Solar Particle Events (SPEs) above 1 keV in FLUKA to determine the photon fluence albedo produced by the Moon’s surface when there is no sunlight and Earthshine. The result is to be distinguished from the gamma-ray spectrum produced by the radioactive decay of radiogenic constituents lying in the surface and interior of the Moon. From the photon fluence we derive the spectrum which can be utilized to examine existing lunar spectral data and to aid future orbiting instrumentation in the measurement of various components of the space-radiation-induced photon luminescence present on the Moon. 相似文献
978.
The Juno Radiation Monitoring (RM) Investigation 总被引:1,自引:0,他引:1
H. N. Becker J. W. Alexander A. Adriani A. Mura A. Cicchetti R. Noschese J. L. Jørgensen T. Denver J. Sushkova A. Jørgensen M. Benn J. E. P. Connerney S. J. Bolton The Selex Galileo Juno SRU Team J. Allison S. Watts V. Adumitroaie E. A. Manor-Chapman I. J. Daubar C. Lee S. Kang W. J. McAlpine T. Di Iorio C. Pasqui A. Barbis P. Lawton L. Spalsbury S. Loftin J. Sun 《Space Science Reviews》2017,213(1-4):507-545
The Radiation Monitoring Investigation of the Juno Mission will actively retrieve and analyze the noise signatures from penetrating radiation in the images of Juno’s star cameras and science instruments at Jupiter. The investigation’s objective is to profile Jupiter’s \(>10\mbox{-MeV}\) electron environment in regions of the Jovian magnetosphere which today are still largely unexplored. This paper discusses the primary instruments on Juno which contribute to the investigation’s data suite, the measurements of camera noise from penetrating particles, spectral sensitivities and measurement ranges of the instruments, calibrations performed prior to Juno’s first science orbit, and how the measurements may be used to infer the external relativistic electron environment. 相似文献
979.
M. A. Janssen J. E. Oswald S. T. Brown S. Gulkis S. M. Levin S. J. Bolton M. D. Allison S. K. Atreya D. Gautier A. P. Ingersoll J. I. Lunine G. S. Orton T. C. Owen P. G. Steffes V. Adumitroaie A. Bellotti L. A. Jewell C. Li L. Li S. Misra F. A. Oyafuso D. Santos-Costa E. Sarkissian R. Williamson J. K. Arballo A. Kitiyakara A. Ulloa-Severino J. C. Chen F. W. Maiwald A. S. Sahakian P. J. Pingree K. A. Lee A. S. Mazer R. Redick R. E. Hodges R. C. Hughes G. Bedrosian D. E. Dawson W. A. Hatch D. S. Russell N. F. Chamberlain M. S. Zawadski B. Khayatian B. R. Franklin H. A. Conley J. G. Kempenaar M. S. Loo E. T. Sunada V. Vorperion C. C. Wang 《Space Science Reviews》2017,213(1-4):139-185
980.
This work presents a review of studies of the Martian magnetic fields during the early Soviet missions to Mars in 1971–1974, which never approached Mars by closer than 1000 km before the experiment with the Magnetometer/Electronic Reflectometer (MAG/ER) on board the Mars Global Surveyor spacecraft, which could descend to altitudes of 80–100 km. At present, the experiment with the magnetometer (MAG) onboard the American MAVEN spacecraft adds new data, but the map of distribution of remnant magnetic fields of Mars and the picture of their interaction with the solar wind are already formed and, at its core, obviously, will not be revised. Thus, it would be very instructive to consider the following in detail: (a) what is already known regarding the features and distribution of remnant magnetic fields on Mars; (b) how they control the interaction of solar wind with a weakly magnetized planet (Mars); and (c) what is its distinction from another nonmagnetized planet (Venus). 相似文献