首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
The spectacular auroral light displays that appear in Earth’s atmosphere around the north and south magnetic poles were once mys
The spectacular auroral light displays that appear in Earth’s atmosphere around the north and south magnetic poles were once mys
admin
2013-01-12
30
问题
The spectacular auroral light displays that appear in Earth’s atmosphere around the north and south magnetic poles were once mysterious phenomena. Now, scientists have data from satellites and ground-based observations from which we know that the auroral brilliance is an immense electrical discharge similar to that occurring in a neon sign.
To understand the cause of auroras, first picture the Earth enclosed by its magnetosphere, a huge region crated by the Earth’s magnetic field. Outside the magneto-sphere, blasting, toward the Earth is the solar wind, a swiftly moving plasma of ionized gases with its own magnetic field. Charged particles in this solar wind speed earth- ward along the solar wind’s magnetic lines of force with a spiraling motion. The Earth’s magnetosphere is a barrier to solar wind, and forces the charged particles of the solar wind to flow around the magnetosphere itself. But in the polar regions, the magnetic lines of force of the Earth and of the solar wind bunch together. Here many of the solar wind’s charged particles break through the magnetosphere and enter Earth’s magnetic field. They then spiral back and forth between the Earth’s magnetic poles very rapidly. In the polar regions, electrons from the solar wind ionize and excite the atoms and molecules of the upper .atmosphere, causing them to emit auroral radiations of visual light.
The colors of an aurora depend on the atoms emitting them. The dominant greenish-white light comes from low energy excitation of oxygen atoms. During huge magnetic storms oxygen atoms also undergo high energy excitation and emit a crimson light. Ex- cited nitrogen atoms contribute bands of color varying from blue to violet.
Viewed from outer space, auroras can be seen as dimly glowing belts wrapped around each of the Earth’s magnetic poles. Each aurora hangs like a curtain of light stretching over the polar regions and into the higher latitudes. When the solar flares that result in magnetic storms and auroral activity are very intense, auroral displays may extend as far as the southern regions of the United States. Studies of auroras have given physicists new information about the behavior of plasmas, which has helped to explain the nature of outer space and is being applied in attempts to harness energy from f the fusion of atoms.
The passage describes the magnetosphere as a barrier because ______.
选项
A、it is strongest in the polar regions and the magnetic lines bunch together
B、it increases the speed of the particles from the solar wind
C、it prevents particles from the solar wind from easily entering the Earth’s atmosphere
D、its position makes it difficult to be observed from the Earth
答案
C
解析
第2段,作者在阐述magnetosphere对太阳风的作用时指出它是一个障碍。由于“it forces the charged particles of the solar wind to flow around the magnetosphere itself” (让太阳风粒子悬浮在磁力层,而不能进入大气层),故选项C正确。
转载请注明原文地址:https://kaotiyun.com/show/7u9O777K
0
考博英语
相关试题推荐
Afterseveral______attemptstosendthemissileintospace,thespacecraftwasfinallylaunchedsuccessfully.
Aperson’scalorierequirementsvary______hislife.
Tosleep.Perchancetofile?FindingspublishedonlinethisweekbytheProceedingsoftheNationalAcademyofSciencesfurther
Whenherealizedhehadbeen______tosignthecontractbyintrigue,hethreatenedtostartlegalproceedingstocanceltheagr
Iwashalfwaybacktothecottagewheremymotherlived______Susancaughtupwithme.
Whydoteensdrink?Reasonsvaryfrom______pressuretofamilypatternstosocialconditioning.
Colorisveryimportanttomostanimalsforithelpsthemtogetalongintheworld.Color【21】tomakeananimaldifficultforit
Duringthepastgeneration,theAmericanmiddle-classfamilythatoncecouldcountonhardworkandfairplaytokeepitselffin
Aparticularareainwhichassumptionsandvaluesdifferbetweenculturesisthatoffriendship.FriendshipsamongAmericansten
Ourshasbecomeasocietyofemployees.AhundredyearsorsoagoonlyoneoutofeveryfiveAmericansatworkwasemployed,i.
随机试题
设函数f(x)在区间[一1,1]上可导,f’(x)0,f(1)
患者女性,57岁,右上腹痛和压痛,体温39.1℃,申请腹部超声检查。作为超声医生,根据该患者的临床症状,应该特别注意检查的脏器是
以PEG6000为基质制栓,润滑剂应选用()。
初产妇,30岁。妊娠38周,自然分娩一健康男婴,胎盘正常娩出。产后1小时发现产妇面色苍白,出冷汗,阴道流血量较多,主诉头晕、心慌和口渴。血压90/50mmHg,脉搏120次/分,既往血小板减少症,无高血压及低血压,无贫血史。该种疾病80%以上发生于
演出艺术,亦可称之为艺术或表演艺术,指的是通过演员在舞台上的现场表演来完成艺术形象创造的艺术形式。下列属于演出艺术的是()。
黄河公司以其房屋作抵押,先后向甲银行借款100万元,乙银行借款300万元,丙银行借款500万元,并依次办理了抵押登记。后丙银行与甲银行商定交换各自抵押权的顺位,并办理了变更登记,但乙银行并不知情。因黄河公司无力偿还三家银行的到期债务,银行拍卖其房屋,仅得价
下列进程关系中,不能用P、V操作来实现的是()。
关于虚拟局域网的描述中,错误的是()。
TheParthenonTheParthenon,abuildinginAthens,Greece,isperhapsoneofthemostmemorablestructuresonEarth.Built25
SteveFossettlandedinhisdestinationaheadofscheduledtimebecause
最新回复
(
0
)