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981.
A. Kontogeorgos P. Tsitsipis X. Moussas G. Preka-Papadema A. Hillaris C. Caroubalos C. Alissandrakis J.-L. Bougeret G. Dumas 《Space Science Reviews》2006,122(1-4):169-179
Fine structure of type IV radio solar bursts with a great variety and complexity often give much information in different
ways and enable estimation of various coronal characteristics. In this work, we expose our new method for fine structure revealing
and separation of two basic kinds of type IV fine structure, as fibers and pulsations. We also estimate frequency drift of
fibers from dynamic spectra, clean from continuous background, with a prototype method using 2-D Fourier transform and we
estimate periodicities of fibers as well as pulsations with continuous wavelet transform. Working with the last method we
found periodicities close to 3 min umbral oscillations and 5 min global solar oscillations. 相似文献
982.
T. G. Forbes J. A. Linker J. Chen C. Cid J. Kóta M. A. Lee G. Mann Z. Mikić M. S. Potgieter J. M. Schmidt G. L. Siscoe R. Vainio S. K. Antiochos P. Riley 《Space Science Reviews》2006,123(1-3):251-302
This chapter provides an overview of current efforts in the theory and modeling of CMEs. Five key areas are discussed: (1) CME initiation; (2) CME evolution and propagation; (3) the structure of interplanetary CMEs derived from flux rope modeling; (4) CME shock formation in the inner corona; and (5) particle acceleration and transport at CME driven shocks. In the section on CME initiation three contemporary models are highlighted. Two of these focus on how energy stored in the coronal magnetic field can be released violently to drive CMEs. The third model assumes that CMEs can be directly driven by currents from below the photosphere. CMEs evolve considerably as they expand from the magnetically dominated lower corona into the advectively dominated solar wind. The section on evolution and propagation presents two approaches to the problem. One is primarily analytical and focuses on the key physical processes involved. The other is primarily numerical and illustrates the complexity of possible interactions between the CME and the ambient medium. The section on flux rope fitting reviews the accuracy and reliability of various methods. The section on shock formation considers the effect of the rapid decrease in the magnetic field and plasma density with height. Finally, in the section on particle acceleration and transport, some recent developments in the theory of diffusive particle acceleration at CME shocks are discussed. These include efforts to combine self-consistently the process of particle acceleration in the vicinity of the shock with the subsequent escape and transport of particles to distant regions. 相似文献
983.
A unique kinetic isotope effect has been found in the formation process of ozone molecules. Isotope enrichments of about 10%
above statistically expected values were first discovered in atmospheric isotopomers 49O3 and 50O3 and later in many other molecular combinations. Most recently the source of this effect was identified through measurement
of isotope-specific ozone formation rate coefficients which show a large variability of over 50%. Ozone molecule formation
is a complex process since different reaction channels contribute to a specific isotopomer. In addition, fast oxygen isotope
exchange reactions determine the abundance of atomic oxygen participating in ozone formation. The isotope enrichments observed
are both pressure and temperature-dependent and they decrease at pressures above 100 mbar and toward lower temperatures. Ozone
possesses not only one of the most unusual isotope anomalies, it also serves as a mediator by transferring heavy oxygen from
the O2 reservoir to other species. Stratospheric isotope composition of CO2 has been recently measured with high accuracy and a pronounced isotopic signature was found which shows that 17O is preferentially transferred from O3 into CO2.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
984.
Radar: The Cassini Titan Radar Mapper 总被引:1,自引:0,他引:1
C. Elachi M. D. Allison L. Borgarelli P. Encrenaz E. Im M. A. Janssen W. T. K. Johnson R. L. Kirk R. D. Lorenz J. I. Lunine D. O. Muhleman S. J. Ostro G. Picardi F. Posa C. G. Rapley L. E. Roth R. Seu L. A. Soderblom S. Vetrella S. D. Wall C. A. Wood H. A. Zebker 《Space Science Reviews》2004,115(1-4):71-110
The Cassini RADAR instrument is a multimode 13.8 GHz multiple-beam sensor that can operate as a synthetic-aperture radar (SAR) imager, altimeter, scatterometer, and radiometer. The principal objective of the RADAR is to map the surface of Titan. This will be done in the imaging, scatterometer, and radiometer modes. The RADAR altimeter data will provide information on relative elevations in selected areas. Surfaces of the Saturn’s icy satellites will be explored utilizing the RADAR radiometer and scatterometer modes. Saturn’s atmosphere and rings will be probed in the radiometer mode only. The instrument is a joint development by JPL/NASA and ASI. The RADAR design features significant autonomy and data compression capabilities. It is expected that the instrument will detect surfaces with backscatter coefficient as low as −40 dB.RADAR Team LeaderThis revised version was published online in July 2005 with a corrected cover date. 相似文献
985.
This paper presents a three-phase (3/spl phi/) switch-mode rectifier (SMR) consisting of three 1 /spl phi/ SMRs, two center-tapped autotransformers and three changeover switches. The ac input sides of three modules are /spl Delta/-connected, and their dc output sides are connected in parallel. As any one module fault occurs, the remaining two modules becomes modified T-connected and continuously perform three-phase rectification with good line drawn power quality. When two constituted 1/spl phi/ modules are faulted, the proposed 3/spl phi/ SMR will be operated as 1/spl phi/ SMR. The quantitative and robust voltage regulation controls for the developed SMR are made to consider the effects of changes of system parameters, operating condition, and number of connected modules. 相似文献
986.
987.
针对过氧化氢水溶液在自分解过程中分解放热引起的温升进行传热分析,建立数学模型,求解得出随着浓度、比热容、分解速率以及散热等因素下的温升变化规律。其结果可以为过氧化氢溶液的储存、输送以及推进燃烧控制提供重要的理论依据,为进一步掌握过氧化氢热化学机理提供理论基础。 相似文献
988.
P. C. Frisch M. Bzowski E. Grün V. Izmodenov H. Krüger J. L. Linsky D. J. McComas E. Möbius S. Redfield N. Schwadron R. Shelton J. D. Slavin B. E. Wood 《Space Science Reviews》2009,146(1-4):235-273
Interstellar material (ISMa) is observed both inside and outside of the heliosphere. Relating these diverse sets of ISMa data provides a richer understanding of both the interstellar medium and the heliosphere. The galactic environment of the Sun is dominated by warm, low-density, partially ionized interstellar material consisting of atoms and dust grains. The properties of the heliosphere are dependent on the pressure, composition, radiation field, ionization, and magnetic field of ambient ISMa. The very low-density interior of the Local Bubble, combined with an expanding superbubble shell associated with star formation in the Scorpius-Centaurus Association, dominate the properties of the local interstellar medium (LISM). Once the heliosphere boundaries and interaction mechanisms are understood, interstellar gas, dust, pickup ions, and anomalous cosmic rays inside of the heliosphere can be directly compared to ISMa outside of the heliosphere. Our understanding of ISMa at the Sun is further enriched when the circumheliospheric interstellar material is compared to observations of other nearby ISMa and the overall context of our galactic environment. The IBEX mission will map the interaction region between the heliosphere and ISMa, and improve the accuracy of comparisons between ISMa inside and outside the heliosphere. 相似文献
989.
The Search Coil Magnetometer for THEMIS 总被引:2,自引:0,他引:2
A. Roux O. Le Contel C. Coillot A. Bouabdellah B. de la Porte D. Alison S. Ruocco M. C. Vassal 《Space Science Reviews》2008,141(1-4):265-275
THEMIS instruments incorporate a tri-axial Search Coil Magnetometer (SCM) designed to measure the magnetic components of waves associated with substorm breakup and expansion. The three search coil antennas cover the same frequency bandwidth, from 0.1 Hz to 4 kHz, in the ULF/ELF frequency range. They extend, with appropriate Noise Equivalent Magnetic Induction (NEMI) and sufficient overlap, the measurements of the fluxgate magnetometers. The NEMI of the searchcoil antennas and associated pre-amplifiers is smaller than 0.76 pT $/\sqrt{\mathrm{Hz}}$ at 10 Hz. The analog signals produced by the searchcoils and associated preamplifiers are digitized and processed inside the Digital Field Box (DFB) and the Instrument Data Processing Unit (IDPU), together with data from the Electric Field Instrument (EFI). Searchcoil telemetry includes waveform transmission, FFT processed data, and data from a filter bank. The frequency range covered depends on the available telemetry. The searchcoils and their three axis structures have been precisely calibrated in a calibration facility, and the calibration of the transfer function is checked on board, usually once per orbit. The tri-axial searchcoils implemented on the five THEMIS spacecraft are working nominally. 相似文献
990.
W. R. Binns M. E. Wiedenbeck M. Arnould A. C. Cummings G. A. de Nolfo S. Goriely M. H. Israel R. A. Leske R. A. Mewaldt G. Meynet L. M. Scott E. C. Stone T. T. von Rosenvinge 《Space Science Reviews》2007,130(1-4):439-449
We have measured the isotopic abundances of neon and a number of other species in the galactic cosmic rays (GCRs) using the
Cosmic Ray Isotope Spectrometer (CRIS) aboard the ACE spacecraft. Our data are compared to recent results from two-component
(Wolf–Rayet material plus solar-like mixtures) Wolf–Rayet (WR) models. The three largest deviations of galactic cosmic ray
isotope ratios from solar-system ratios predicted by these models, 12C/16O, 22Ne/20Ne, and 58Fe/56Fe, are very close to those observed. All of the isotopic ratios that we have measured are consistent with a GCR source consisting
of ∼20% of WR material mixed with ∼80% material with solar-system composition. Since WR stars are evolutionary products of
OB stars, and most OB stars exist in OB associations that form superbubbles, the good agreement of our data with WR models
suggests that OB associations within superbubbles are the likely source of at least a substantial fraction of GCRs. In previous
work it has been shown that the primary 59Ni (which decays only by electron-capture) in GCRs has decayed, indicating a time interval between nucleosynthesis and acceleration
of >105 y. It has been suggested that in the OB association environment, ejecta from supernovae might be accelerated by the high
velocity WR winds on a time scale that is short compared to the half-life of 59Ni. Thus the 59Ni might not have time to decay and this would cast doubt upon the OB association origin of cosmic rays. In this paper we
suggest a scenario that should allow much of the 59Ni to decay in the OB association environment and conclude that the hypothesis of the OB association origin of cosmic rays
appears to be viable. 相似文献