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251.
252.
As part of our study of the larger-scale remanent magnetic field of the Moon, we have examined the effects of cratering in
an otherwise spherically symmetrical shell magnetized by a concentric dipolar magnetic fieldH
o to an intensity of magnetizationc
H
o, wherec is a constant. In our initial model, we assume that the material excavated from the craters is distributed with random orientation
and thus does not contribute to the remanent dipole momentM
g
. We further assume that the mare fill does not contribute significantly toM
g
. We choose the magnetizing dipole momentM
o and the constantc such that the magnitude of the productcH
o ≃ 3 × 10−4Г at the outer surface of the shell in the equatorial plane of the dipole. This value of the intensity of remanent magnetization
was chosen to be within the range 10−7−10−3Г’; the intensities of thermo-remanent magnetization exhibited by Apollo samples. Finally, we use the locations and diameters
of the 10 largest craters on the Moon and the depth-to-diameter ratios of Pike’s formulation to model approximately the excavation
of the magnetized shell.
The remanent dipole momentM
g
was calculated for each of three orthogonal orientations of the magnetizing dipoleM
o. The three magnitudes ofM
g
fall in the range 4 × 1018−1 × 1019Г cm3 which is close to the upper limit of 1019Г cm3 estimated forM
g
from the field measurements obtained with the Apollo subsatellites. Further, the distribution of the craters is such as to
produce a significant transverse component ofM
g
with acute angles between the spin axis andM
g
in the range 51°–77°. 相似文献
253.
The cooling of electrons by vibrational and rotational excitation of molecular hydrogen plays an important role in the thermal balance of electrons in atmospheres containing significant amounts of H2. Calculations of vibrational and rotational cooling rates of electrons by H2 are described. Results are presented for a wide range of electron and neutral temperatures. Analytical formulae for some of the cooling rates are also provided. 相似文献
254.
Robert A. Howland Jr. 《Celestial Mechanics and Dynamical Astronomy》1979,19(2):139-145
Through the introduction of a term at each order of the generating function dependent only on the long-period variables, a technique is shown whereby both short- and long-period variables in a degenerate Hamiltonian can be eliminated simultaneously in one transformation with the von Zeipel method, rather than the traditionally separate transformations. The technique is applied to the lunar theory as an example. 相似文献
255.
1986年2月4日太阳耀斑的演化研究 总被引:1,自引:0,他引:1
本文根据乌鲁木齐天文站的H_α耀斑及3.2cm射电流量观侧资料、云南天文台的黑子精细结构照相和Marshall Space Flight Center的向量磁场图,对1986年2月4日的六个耀斑的形态相关及演化联系,特别是0736UT 4B/3X大耀斑的发展过程进行了综合分析。主要结果是: 1.4日大耀斑的初始亮点和闪光相的主要形态演化,与活动区中沿中性线新浮现的强大电流/磁环系密切相关。后者的主要标志是沿中性线的长的剪切半影纤维及它两端的偶极旋涡黑子群(1_3F_3)。 2.上述大耀斑与1972年8月4日0624 UT大耀斑爆发的磁场背景及主要形态特征相似,表明两者的储能和触发机制可能相同。 3.大耀斑爆发的H_α初始亮点,双带出现,环系形成,亮物质抛射和吸收冕珥等现象同3.2cm射电流量的变化在时间上有较好的对应关系。 4.重复性的前期小耀斑爆发位置和发展趋势与大耀斑的主要形态及演化特征相似。它们相对于剪切的纵场中性线两侧的位置相近或相同。因而,可以看作上述强大电流/磁环系不稳性发展过程中的前置小爆发。 相似文献
256.
E. W. Cliver S. W. Kahler H. V. Cane M. J. Koomen D. J. Michels R. A. Howard N. R. Sheeley Jr. 《Solar physics》1983,89(1):181-193
We use a variety of ground-based and satellite measurements to identify the source of the ground level event (GLE) beginning near 06∶30 UT on 21 August, 1979 as the 2B flare with maximum at ~06∶15 UT in McMath region 16218. This flare differed from previous GLE-associated flares in that it lacked a prominent impulsive phase, having a peak ~9 GHz burst flux density of only 27 sfu and a ?20 keV peak hard X-ray flux of ?3 × 10-6 ergs cm-2s-1. Also, McMath 16218 was magnetically less complex than the active regions in which previous cosmic-ray flares have occurred, containing essentially only a single sunspot with a rudimentary penumbra. The flare was associated with a high speed (?700 km s-1) mass ejection observed by the NRL white light coronagraph aboard P78-1 and a shock accelerated (SA) event observed by the low frequency radio astronomy experiment on ISEE-3. 相似文献
257.
258.
Plans for the deployment of a comprehensive set of instruments designed to study the high-energy emissions of solar flares have been developed as part of a series of studies for an Advanced Solar Observatory (ASO). These studies have identified the Space Station as the preferred mode for the deployment of the full ASO. The accident of the Space Shuttle Challenger in 1986, and the growth in the estimated costs for the Space Station during the fiscal year 1989 budget discussions, have created an uncertain climate within the United States Space Program, making it difficult to predict the schedule for major programs such as the ASO. Approaches to the deployment of instruments for the study of high-energy solar emissions alone, or in conjunction with other solar instruments are discussed. As an independent entity the High-Energy Facility could be on a co-orbiting platform. 相似文献
259.
260.
The dynamics of grain motion through gas are examined in terms of the injection of isotopically anomalous (compared to solar abundances) material into the early solar nebula. Calculations indicate that the injected grains cannot penetrate to the center of any of a range of reasonable configurations, suggesting the formation of an edge region enriched in injected material. Furthermore, the dynamical behavior of grains in turbulent flows indicates that pockets of grains can have some resistance to turbulent diffusion. The constraints developed here are used to delineate a set of consistent, injected-grain models for the origin of the isotopic anomalies in meteorite inclusions.Invited contribution to the Proceedings of a Workshop onThermodynamics and Kinetics of Dust Formation in the Space Medium held at the Lunar and Planetary Institute, Houston, 6–8 September, 1978. 相似文献