太阳活动周期与表面环流有关-凯发k8官网

太阳活动周期与表面环流有关
文章来源:未知 文章作者:meng 发布时间:2010-08-13 00:26 字体: [ ] 
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a new analysis of the unusually long solar cycle that ended in 2008 suggests that one reason for the long cycle could be a stretching of the sun's conveyor belt, a current of 1(等离子体,血浆) that circulates(传播,循环) between the sun's equator(赤道) and its poles. the results should help scientists better understand the factors controlling the 2 of solar cycles and could lead to better predictions. the study was conducted by mausumi dikpati, peter gilman, and giuliana de toma, all scientists in the high altitude 3 at the national center for 4 research (ncar), and by roger ulrich at the university of california, los angeles. it appeared on july 30 in geophysical research letters. the study was funded by the national science foundation, ncar's sponsor, and by nasa.

the sun goes through cycles 5 approximately 11 years that include phases with increased magnetic activity, more sunspots(太阳黑子,雀斑) , and more solar 6, than phases with less activity. the level of activity on the sun can affect navigation and communications systems on earth. puzzlingly, solar cycle 23, the one that ended in 2008, lasted longer than previous cycles, with a prolonged(延长的,拖延的) phase of low activity that scientists had difficulty explaining.

the new ncar analysis suggests that one reason for the long cycle could be changes in the sun's conveyor belt. just as earth's global ocean circulation transports water and heat around the planet, the sun has a conveyor belt in which plasma flows along the surface toward the poles, sinks, and returns toward the equator, transporting magnetic 7(磁通量) along the way.

"the key for explaining the long duration of cycle 23 with our dynamo(发电机) model is the observation of an unusually long conveyor belt during this cycle," dikpati says. "conveyor belt theory indicates that shorter belts, such as observed in cycle 22, should be more common in the sun."

recent measurements gathered and 8 by ulrich and colleagues show that in solar cycle 23, the poleward(向极的) flow extended all the way to the poles, while in previous solar cycles the flow turned back toward the equator at about 60 degrees 9. furthermore, as a result of mass conservation, the return flow was slower in cycle 23 than in previous cycles.

in their paper, dikpati, gilman, and de toma used simulations to model how the solar plasma conveyor belt 10 the solar cycle. the authors found that the longer conveyor belt and slower return flow could have caused the longer duration of cycle 23.

the ncar team's computer model, known as the predictive flux-transport dynamo model, simulates the evolution of magnetic fields in the outer third of the sun's interior (the solar convection zone). it provides a physical basis for projecting the nature of upcoming solar cycles from the properties of previous cycles, as opposed to 11 models that emphasize 12 between cycles. in 2004, the model successfully predicted that cycle 23 would last longer than usual.

according to dikpati, the duration of a solar cycle is probably 13 by the strength of the sun's meridional flow(经向气流) . the combination of this flow and the lifting and twisting of magnetic fields near the bottom of the convection zone generates the observed symmetry(对称,整齐) of the sun's global field with respect to(关于,至于) the solar equator.

"this study highlights the importance of monitoring and improving measurement of the sun's meridional circulation," ulrich says. "in order to improve predictions of the solar cycle, we need a strong effort to understand large-scale patterns of solar plasma motion."



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1 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。
2 rguzgc     
n.时间安排,时间选择
参考例句:
  • the timing of the meeting is not convenient.会议的时间安排不合适。
  • the timing of our statement is very opportune.我们发表声明选择的时机很恰当。
3 hrgzp     
n.天文台,气象台,瞭望台,观测台
参考例句:
  • guy's house was close to the observatory.盖伊的房子离天文台很近。
  • officials from greenwich observatory have the clock checked twice a day.格林威治天文台的职员们每天对大钟检查两次。
4 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。
5 ipcz02     
adj.永久的,永恒的;vbl.持续,维持
参考例句:
  • the lasting war debased the value of the dollar.持久的战争使美元贬值。
  • we hope for a lasting settlement of all these troubles.我们希望这些纠纷能获得永久的解决。
6 2c4a86d21d1a57023e2985339a79f9e2     
n.喇叭裤v.(使)闪耀( flare的第三人称单数 );(使)(船舷)外倾;(使)鼻孔张大;(使)(衣裙、酒杯等)呈喇叭形展开
参考例句:
  • the side of a ship flares from the keel to the deck. 船舷从龙骨向甲板外倾。 来自《简明英汉词典》
  • he's got a fiery temper and flares up at the slightest provocation. 他是火爆性子,一点就着。 来自《现代汉英综合大词典》
7 sg4zj     
n.流动;不断的改变
参考例句:
  • the market is in a constant state of flux.市场行情在不断变化。
  • in most reactors,there is a significant flux of fast neutrons.在大部分反应堆中都有一定强度的快中子流。
8 483f1acae53789fbee273a644fdcda80     
v.分析( analyze的过去式和过去分词 );分解;解释;对…进行心理分析
参考例句:
  • the doctors analyzed the blood sample for anemia. 医生们分析了贫血的血样。 来自《简明英汉词典》
  • the young man did not analyze the process of his captivation and enrapturement, for love to him was a mystery and could not be analyzed. 这年轻人没有分析自己蛊惑著迷的过程,因为对他来说,爱是个不可分析的迷。 来自《简明英汉词典》
9 i23xv     
n.纬度,行动或言论的自由(范围),(pl.)地区
参考例句:
  • the latitude of the island is 20 degrees south.该岛的纬度是南纬20度。
  • the two cities are at approximately the same latitude.这两个城市差不多位于同一纬度上。
10 tzuzg0     
adj.不自然的,假装的
参考例句:
  • she showed an affected interest in our subject.她假装对我们的课题感到兴趣。
  • his manners are affected.他的态度不自然。
11 bu3wa     
adj.统计的,统计学的
参考例句:
  • he showed the price fluctuations in a statistical table.他用统计表显示价格的波动。
  • they're making detailed statistical analysis.他们正在做具体的统计分析。
12 4a9b6fe1ddc2671881c9aa3d6cc07e8e     
相互的关系( correlation的名词复数 )
参考例句:
  • one would expect strong and positive correlations between both complexes. 人们往往以为这两个综合体之间有紧密的正相关。
  • the correlations are of unequal value. 这些对应联系的价值并不相同。
13 duszmp     
adj.坚定的;有决心的
参考例句:
  • i have determined on going to tibet after graduation.我已决定毕业后去西藏。
  • he determined to view the rooms behind the office.他决定查看一下办公室后面的房间。
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