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241.
242.
In this paper we performed the selection of sharp and large solar wind ion flux changes and comparison of them by simultaneous observations onboard two or three spacecraft. It was shown that these sharp changes survive on the way up to million km or even sharpen on this way. 相似文献
243.
对中国大陆5.0级以上强震的后续地震进行了分析,按成因将其划分为剩余型、诱导型和后生型3类。讨论了3种后续地震的主要特征及其在大震震源机理研究和地震预报中的意义。 相似文献
244.
Masateru Ishiguro 《Icarus》2008,193(1):96-104
A thin, bright dust cloud, which is associated with the Rosetta mission target object (67P/Churyumov-Gerasimenko), was observed after the 2002 perihelion passage. The neckline structure or dust trail nature of this cloud is controversial. In this paper, we definitively identify the dust trail and the neckline structure using a wide-field CCD camera attached to the Kiso 1.05-m Schmidt telescope. The dust trail of 67P/Churyumov-Gerasimenko was evident as scattered sunlight in all images taken between September 9, 2002 and February 1, 2003, whereas the neckline structure became obvious only after late 2002. We compared our images with a semi-analytical dynamic model of dust grains emitted from the nucleus. A fading of the surface brightness of the dust trail near the nucleus enabled us to determine the typical maximum size of the grains. Assuming spherical compact particles with a mass density of 103 kg m−3 and an albedo of 0.04, we deduced that the maximum diameter of the dust particles was approximately 1 cm. We found that the mass-loss rate of the comet at the perihelion was on or before the 1996 apparition, while the mass-loss rate averaged over the orbit reached . The result is consistent with the studies of the dust cloud emitted in the 2002/2003 return. Therefore, we can infer that the activity of 67P/Churyumov-Gerasimenko has showed no major change over the past dozen years or so, and the largest grains are cyclically injected into the dust tube lying along the cometary orbit. 相似文献
245.
Evidence of asteroid surface features as regolith grains and larger boulders implies resurfacing possibility due to external
forces such as gravitational tidal force during close planet encounters. Motion of a meteoroid released from an asteroid in
the gravitational fields of the asteroid and the Earth is modeled. We are interested mainly in a distance between the meteoroid
and the asteroid as a function of the time. Applications to Itokawa and some close approaching NEAs are presented. 相似文献
246.
Assuming that similar organic components as in comet 81P/Wild 2 are present in incoming meteoroids, we try to anticipate the
observable signatures they would produce for meteor detection techniques. In this analysis we consider the elemental and organic
components in cometary aggregate interplanetary dust particles and laboratory analyses of inter- and circumstellar carbon
dust analogues. On the basis of our analysis we submit that (semi) quantitative measurements of H, N and C produced during
meteor ablation will open an entire new aspect to using meteoroids as tracers of these volatile element abundances in active
comets and their contributions to the mesospheric metal layers. 相似文献
247.
Volume currents in the magnetosheath region are calculated within the framework of a new analytical model. Magnetic field structure in the region is found, satisfying boundary conditions on the bow shock and the magnetopause, and then volume currents are calculated using the Maxwell equation. Surface bow shock and magnetopause currents are calculated, too. Free parameters of the model are interplanetary magnetic field, Mach number of the solar wind flow, distances to the bow shock and to the magnetopause, and field compression at the magnetopause. 相似文献
248.
C. Courtois R. A. D. Grundy A. D. Ash D. M. Chambers R. O. Dendy K. G. Mcclements N. C. Woolsey 《Astrophysics and Space Science》2005,298(1-2):93-98
Results from a scaled, collision-free, laser-plasma experiment designed to address aspects of collisionless plasma interaction
in a high-plasma β supernova remnant (SNR) are discussed. Ideal magneto-hydrodynamic scaling indicates that the experimental
plasma matches the SNR plasma at 500 ps. Experimental data show that the magnetic field can alter the plasma density profile
when two similar plasmas interact in a colliding geometry. These results are not explained by magnetic-field pressure; they
do, however, suggest magnetic field penetration that localizes the plasma particles to the Larmor radius, which appears smaller
than the size of the experiment and the particle mean-free paths and may thus increase the effective collisionality of the interacting plasma system. 相似文献
249.
The effects of a Halo Coronal Mass Ejection (CME) erupted on 4 April 2000 are studied and reported here. The effect of such CME on the interplanetary medium (IPM) is sensed by the Interplanetary Scintillation (IPS) recorded at Rajkot. The Solar Observations of this CME and associated events, like Solar Energetic Particles (SEP) and flare, are presented. CME events with high speeds and negative magnetic field components have higher possibility of penetrating the earth's shield, viz. the magnetosphere. The 4 April 2000 CME with a high speed and southward component of IMF produced a big geomagnetic storm with Dst reaching . Simultaneous ionospheric effects in F layer heights and auroral observations are reported. Such events are important in Space Weather Studies as these pose hazards to space operations including satellite communications and surveillance systems. 相似文献
250.
In this work, solar flare energetic particle fluxes (Ee 42 keV) observed by the HI-SCALE instrument onboard Ulysses, a spacecraft that is probing the heliosphere in 3-D, are utilized as diagnostics of the large-scale structure and topology of the interplanetary magnetic field (IMF) embedded within two well-identified interplanetary coronal mass ejection (ICME) structures. On the basis of the energetic solar flare particle observations firm conclusions are drawn on whether the detected ICMEs have been detached from the solar corona or are still magnetically anchored to it when they arrive at 2.5 AU. From the development of the angular distributions of the particle intensities, we have inferred that portions of the ICMEs studied consisted of both open and closed magnetic field lines. Both ICMEs present a filamentary structure comprising magnetic filaments with distinct electron anisotropy characteristics. Subsequently, we studied the evolution of the anisotropies of the energetic electrons along the magnetic field loop-like structure of one ICME and computed the characteristic decay time of the anisotropy which is a measure of the amount of scattering that the trapped electron population underwent after injection at the Sun. 相似文献