高层大气中极端高能粒子的来源
文章来源:未知 文章作者:enread 发布时间:2013-12-24 07:37 字体: [ ]  进入论坛
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New research published in the journal Nature resolves decades of scientific controversy1 over the origin of the extremely energetic particles known as ultra-relativistic electrons in Earth's near-space environment and is likely to influence our understanding of planetary magnetospheres(磁气圈) throughout the universe. Discovering the processes that control the formation and ultimate loss of these electrons in the Van Allen radiation belts -- the rings of highly charged particles that encircle Earth at a range of about 1,000 to 50,000 kilometers above the planet's surface -- is a primary science objective of the recently launched NASA Van Allen Probes mission. Understanding these mechanisms3 has important practical applications, because the enormous amounts of radiation trapped within the belts can pose a significant hazard to satellites and spacecraft, as well astronauts performing activities outside a craft.
 
Ultra-relativistic electrons in Earth's outer radiation belt can exhibit pronounced variability in response to activity on the sun and changes in the solar wind, but the dominant4 physical mechanism2 responsible for radiation-belt electron acceleration5 has remained unresolved for decades. Two primary candidates for this acceleration have been "inward radial diffusive6(普及的,散布性的) transport" and "local stochastic acceleration" by very low-frequency plasma7 waves.
 
In research published Dec. 19 in Nature, lead author Richard Thorne, a distinguished8 professor of atmospheric9 and oceanic sciences in the UCLA College of Letters and Science, and his colleagues report on high-resolution satellite measurements of high-energy electrons during a geomagnetic storm on Oct. 9, 2012, which they have numerically modeled using a newly developed data-driven global wave model.
 
Their analysis reveals that scattering10 by intense, natural very low-frequency radio waves known as "chorus" in Earth's upper atmosphere is primarily responsible for the observed relativistic electron build-up.
 
The team's detailed11 modeling, together with previous observations of peaks in electron phase space density12 reported earlier this year by Geoff Reeves and colleagues in the journal Science, demonstrates the remarkable13 efficiency of natural wave acceleration in Earth's near-space environment and shows that radial diffusion14 was not responsible for the observed acceleration during this storm, Thorne said.
 
Co-authors of the new research include Qianli Ma, a graduate student who works in Thorne's lab; Wen Li, Binbin Ni and Jacob Bortnik, researchers in Thorne's lab; and members of the science teams on the Van Allen Probes, including Harlan Spence of the University of New Hampshire (principal investigator15 for RBSP-ECT) and Craig Kletzing of the University of Iowa (principal investigator for EMFISIS).
 
The local wave-acceleration process is a "universal physical process" and should also be effective in the magnetospheres of Jupiter, Saturn16 and other magnetized plasma environments in the cosmos17, Thorne said. He thinks the new results from the detailed analysis of Earth will influence future modeling of other planetary magnetospheres.
 
The Van Allen radiation belts were discovered in Earth's upper atmosphere in 1958 by a team led by space scientist James Van Allen.
 
The new research was funded by the NASA, which launched the twin Van Allen probes in the summer of 2012.


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1 controversy 6Z9y0     
n.争论,辩论,争吵
参考例句:
  • That is a fact beyond controversy.那是一个无可争论的事实。
  • We ran the risk of becoming the butt of every controversy.我们要冒使自己在所有的纷争中都成为众矢之的的风险。
2 mechanism zCWxr     
n.机械装置;机构,结构
参考例句:
  • The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
  • The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。
3 mechanisms d0db71d70348ef1c49f05f59097917b8     
n.机械( mechanism的名词复数 );机械装置;[生物学] 机制;机械作用
参考例句:
  • The research will provide direct insight into molecular mechanisms. 这项研究将使人能够直接地了解分子的机理。 来自《简明英汉词典》
  • He explained how the two mechanisms worked. 他解释这两台机械装置是如何工作的。 来自《简明英汉词典》
4 dominant usAxG     
adj.支配的,统治的;占优势的;显性的;n.主因,要素,主要的人(或物);显性基因
参考例句:
  • The British were formerly dominant in India.英国人从前统治印度。
  • She was a dominant figure in the French film industry.她在法国电影界是个举足轻重的人物。
5 acceleration ff8ya     
n.加速,加速度
参考例句:
  • All spacemen must be able to bear acceleration.所有太空人都应能承受加速度。
  • He has also called for an acceleration of political reforms.他同时呼吁加快政治改革的步伐。
6 diffusive 142a3e0f4cf6590eb56586a5187666c0     
adj.散布性的,扩及的,普及的
参考例句:
  • He had only the tendency to that diffusive form of gambling. 他有的是一种逢场作戏的赌博方式。 来自辞典例句
  • He suggested that the varieties tested had different diffusive resistance to CO他提出,供试验用的品种对二氧化碳有不同的扩散阻力。 来自辞典例句
7 plasma z2xzC     
n.血浆,细胞质,乳清
参考例句:
  • Keep some blood plasma back for the serious cases.留一些血浆给重病号。
  • The plasma is the liquid portion of blood that is free of cells .血浆是血液的液体部分,不包含各种细胞。
8 distinguished wu9z3v     
adj.卓越的,杰出的,著名的
参考例句:
  • Elephants are distinguished from other animals by their long noses.大象以其长长的鼻子显示出与其他动物的不同。
  • A banquet was given in honor of the distinguished guests.宴会是为了向贵宾们致敬而举行的。
9 atmospheric 6eayR     
adj.大气的,空气的;大气层的;大气所引起的
参考例句:
  • Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
  • Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。
10 scattering 91b52389e84f945a976e96cd577a4e0c     
n.[物]散射;散乱,分散;在媒介质中的散播adj.散乱的;分散在不同范围的;广泛扩散的;(选票)数量分散的v.散射(scatter的ing形式);散布;驱散
参考例句:
  • The child felle into a rage and began scattering its toys about. 这孩子突发狂怒,把玩具扔得满地都是。 来自《简明英汉词典》
  • The farmers are scattering seed. 农夫们在播种。 来自《简明英汉词典》
11 detailed xuNzms     
adj.详细的,详尽的,极注意细节的,完全的
参考例句:
  • He had made a detailed study of the terrain.他对地形作了缜密的研究。
  • A detailed list of our publications is available on request.我们的出版物有一份详细的目录备索。
12 density rOdzZ     
n.密集,密度,浓度
参考例句:
  • The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
  • The region has a very high population density.该地区的人口密度很高。
13 remarkable 8Vbx6     
adj.显著的,异常的,非凡的,值得注意的
参考例句:
  • She has made remarkable headway in her writing skills.她在写作技巧方面有了长足进步。
  • These cars are remarkable for the quietness of their engines.这些汽车因发动机没有噪音而不同凡响。
14 diffusion dl4zm     
n.流布;普及;散漫
参考例句:
  • The invention of printing helped the diffusion of learning.印刷术的发明有助于知识的传播。
  • The effect of the diffusion capacitance can be troublesome.扩散电容会引起麻烦。
15 investigator zRQzo     
n.研究者,调查者,审查者
参考例句:
  • He was a special investigator for the FBI.他是联邦调查局的特别调查员。
  • The investigator was able to deduce the crime and find the criminal.调查者能够推出犯罪过程并锁定罪犯。
16 Saturn tsZy1     
n.农神,土星
参考例句:
  • Astronomers used to ask why only Saturn has rings.天文学家们过去一直感到奇怪,为什么只有土星有光环。
  • These comparisons suggested that Saturn is made of lighter materials.这些比较告诉我们,土星由较轻的物质构成。
17 cosmos pn2yT     
n.宇宙;秩序,和谐
参考例句:
  • Our world is but a small part of the cosmos.我们的世界仅仅是宇宙的一小部分而已。
  • Is there any other intelligent life elsewhere in the cosmos?在宇宙的其他星球上还存在别的有智慧的生物吗?
TAG标签: space earth electrons
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