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81.
Quantitative estimation of helium-3 spatial distribution in the lunar regolith layer 总被引:2,自引:0,他引:2
3He (helium-3) in the lunar regolith implanted by the solar wind is one of the most valuable resources because of its potential as a fusion fuel. The abundance of 3He in the lunar regolith is related to solar wind flux, lunar surface maturity and TiO2 content, etc. A model of solar wind flux, which takes account of variations due to shielding of the nearside when the Moon is in the Earth's magnetotail, is used to present a global distribution of relative solar wind flux over the lunar surface. Using Clementine UV/VIS multispectral data, the global distribution of lunar surface optical maturity (OMAT) and the TiO2 content in the lunar regolith are calculated. Based on Apollo regolith samples, a linear relation between 3He abundance and normalized solar wind flux, optical maturity, and TiO2 content is presented. To simulate the brightness temperature of the lunar surface, which is the mission of the Chinese Chang-E project's multichannel radiometers, a global distribution of regolith layer thickness is first empirically constructed from lunar digital elevation mapping (DEM). Then an inversion approach is presented to retrieve the global regolith layer thickness. It finally yields the total amount of 3He per unit area in the lunar regolith layer, which is related to the regolith layer thickness, solar wind flux, optical maturity and TiO2 content, etc. The global inventory of 3He is estimated as 6.50×108 kg, where 3.72×108 kg is for the lunar nearside and 2.78×108 kg is for the lunar farside. 相似文献
82.
Peter Bochsler 《Astronomy and Astrophysics Review》2007,14(1):1-40
Ions heavier than 4He are treated as “minors” in the solar wind. This is justified for many applications since minor ions have no significant
influence on the dynamics of the interplanetary plasma. However, minor ions carry information on many aspects of the formation,
on the acceleration and on the transfer of solar plasma from the corona into the interplanetary space. This review concentrates
on various aspects of minor ions as diagnostic tracers. The elemental abundance patterns of the solar wind are shaped in the
chromosphere and in the lower transition region by processes, which are not fully understood at this moment. Despite this
lack of detailed understanding, observed abundance patterns have been classified and are now commonly used to characterize
the sources, and to trace back solar-wind flows to their origins in the solar atmosphere. Furthermore, the solar wind is the
most important source of information for solar isotopic abundances and for solar abundances of volatile elements. In order
to fully exploit this information, a comprehensive understanding of elemental and isotopic fractionation processes is required.
We provide observational clues to distinguish different processes at work. 相似文献
83.
怀柔观测基地的多通道太阳望远镜是通过数十个电机调节晶体偏转角度实现多波带同时观测的自动控制。原有的计算机是通过一个串行接口控制若干个调波带的电机,响应时间长,速度慢且技术比较落后。本文利用当今流行的USB2.0芯片CYPRESS EZ-USB改造原有的串口通信控制系统,大大提高了响应的速度,同时,为解决一个USB应用程序控制多个电机转动的问题,提出了一种"编号"的方法。这样每个USB设备不论其插入顺序,PC主机都能通过识别其固定编号而加以区分,PC主机可以通过4个USB接口(16个电机)控制多通道太阳望远镜滤光嚣的调制角度,实现自动控制。这为大规模改造其他计算机接口提供了研制基础。 相似文献
84.
R. P. Kane 《Solar physics》2007,246(2):471-485
Many methods of predictions of sunspot maximum number use data before or at the preceding sunspot minimum to correlate with
the following sunspot maximum of the same cycle, which occurs a few years later. Kane and Trivedi (Solar Phys. 68, 135, 1980) found that correlations of R
z(max) (the maximum in the 12-month running means of sunspot number R
z) with R
z(min) (the minimum in the 12-month running means of sunspot number R
z) in the solar latitude belt 20° – 40°, particularly in the southern hemisphere, exceeded 0.6 and was still higher (0.86)
for the narrower belt > 30° S. Recently, Javaraiah (Mon. Not. Roy. Astron. Soc.
377, L34, 2007) studied the relationship of sunspot areas at different solar latitudes and reported correlations 0.95 – 0.97 between minima and maxima of sunspot areas at low latitudes
and sunspot maxima of the next cycle, and predictions could be made with an antecedence of more than 11 years. For the present
study, we selected another parameter, namely, SGN, the sunspot group number (irrespective of their areas) and found that SGN(min) during a sunspot minimum year at latitudes > 30° S had a correlation
+0.78±0.11 with the sunspot number R
z(max) of the same cycle. Also, the SGN during a sunspot minimum year in the latitude belt (10° – 30° N) had a correlation +0.87±0.07 with the
sunspot number R
z(max) of the next cycle. We obtain an appropriate regression equation, from which our prediction for the coming cycle 24 is R
z(max )=129.7±16.3. 相似文献
85.
The solar wind conditions at one astronomical unit (AU) can be strongly disturbed by interplanetary coronal mass ejections
(ICMEs). A subset, called magnetic clouds (MCs), is formed by twisted flux ropes that transport an important amount of magnetic
flux and helicity, which is released in CMEs. At 1 AU from the Sun, the magnetic structure of MCs is generally modeled by
neglecting their expansion during the spacecraft crossing. However, in some cases, MCs present a significant expansion. We
present here an analysis of the huge and significantly expanding MC observed by the Wind spacecraft during 9 – 10 November 2004. This MC was embedded in an ICME. After determining an approximate orientation for
the flux rope using the minimum variance method, we obtain a precise orientation of the cloud axis by relating its front and
rear magnetic discontinuities using a direct method. This method takes into account the conservation of the azimuthal magnetic
flux between the inbound and outbound branches and is valid for a finite impact parameter (i.e., not necessarily a small distance between the spacecraft trajectory and the cloud axis). The MC is also studied using dynamic
models with isotropic expansion. We have found (6.2±1.5)×1020 Mx for the axial flux and (78±18)×1020 Mx for the azimuthal flux. Moreover, using the direct method, we find that the ICME is formed by a flux rope (MC) followed
by an extended coherent magnetic region. These observations are interpreted by considering the existence of a previously larger
flux rope, which partially reconnected with its environment in the front. We estimate that the reconnection process started
close to the Sun. These findings imply that the ejected flux rope is progressively peeled by reconnection and transformed
to the observed ICME (with a remnant flux rope in the front part). 相似文献
86.
David Alexander 《Astrophysics and Space Science》2007,307(1-3):197-202
The solar atmosphere displays a wide variety of dynamic phenomena driven by the interaction of magnetic fields and plasma.
In particular, plasma jets in the solar chromosphere and corona, coronal heating, solar flares and coronal mass ejections
all point to the presence of magnetic phenomena such as reconnection, flux cancellation, the formation of magnetic islands,
and plasmoids. While we can observe the signatures and gross features of such phenomena we cannot probe the essential physics
driving them, given the spatial resolution of current instrumentation. Flexible and well-controlled laboratory experiments,
scaled to solar parameters, open unique opportunities to reproduce the relevant unsteady phenomena under various simulated
solar conditions. The ability to carefully control these parameters in the laboratory allows one to diagnose the dynamical
processes which occur and to apply the knowledge gained to the understanding of similar processes on the Sun, in addition
directing future solar observations and models. This talk introduces the solar phenomena and reviews the contributions made
by laboratory experimentation. 相似文献
87.
88.
89.
本文考虑到干涉仪对电离层中不同尺度不规则性的滤波作用、结合密云米波综合孔径系统、提出了电离层E_(?)层是电离层不规则性影响该系统的主要根源。不规则性的尺度约在700~1000米的范围。再考虑到E_(?)层的漂移运动,提出了文中所描述的模型。用电子计算机进行了E_(?)层对综合射束污染的模拟计算,结果指出:射束主瓣的增益下降约10%,副瓣由13%增大到18%;综合射束在赤经方向出现不对称性,从而引起约0.6秒的赤经误差;射束的边缘处和两个扇形区出现了杂瓣。 相似文献
90.
本文给出了一个在观测中辨别光球横向磁场指向的一个判据。并证明了光球横向电流与横向磁场的指向无关,因而完全可以由向量磁象仪测定。 相似文献