首页
登录
职称英语
The spectacular auroral light displays that appear in Earth’s atmosphere arou
The spectacular auroral light displays that appear in Earth’s atmosphere arou
游客
2025-04-26
31
管理
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. [br] Auroras may be seen in the southern regions of the United States when ______.
选项
A、the speed of the solar wind is reduced
B、they are wrapped around the Earth’s magnetic poles
C、magnetic storms do not affect the Earth
D、solar flares are very intense
答案
D
解析
文中第4段,作者指山when the solar flares are very intense, auroral displays就能延伸到the southern regions of the United States,故选项D正确。
转载请注明原文地址:https://tihaiku.com/zcyy/4054705.html
相关试题推荐
It’softenamistaketo______appearance:thatpoor-lookingindividualisanythin
ThespectacularaurorallightdisplaysthatappearinEarth’satmospherearou
ThespectacularaurorallightdisplaysthatappearinEarth’satmospherearou
ThemoleculesofcarbondioxideintheEarth’satmosphereaffecttheheatbal
ThemoleculesofcarbondioxideintheEarth’satmosphereaffecttheheatbal
ThemoleculesofcarbondioxideintheEarth’satmosphereaffecttheheatbal
Theappearanceoftheusedcaris______,it’smuchnewerthanitreallyis.A、de
Withinhoursofappearingontelevisiontoannouncetheendofconscription,
Withinhoursofappearingontelevisiontoannouncetheendofconscription,
Withinhoursofappearingontelevisiontoannouncetheendofconscription,
随机试题
“依约履行是法院发出的命令,它构成明确指示要求合同一方当事人履行其按合同条款应承担的义务。”指出法院判决依约履行的原则。依约履行意味着当事人对其合同的实际履行,
Arectanglehasfourstraightsidesat90°toeachother,twoofwhicharelonge
男性,70岁,体检时发现PSA明显升高。前列腺穿刺检查,病理诊断为前列腺癌Gle
下列有关财产清查的叙述中,正确的有()。A、财产清查是会计监督职能的核心内容
下列关于正常新生儿的描述,正确的是A.生理体重下降一般达到出生体重的15% B
下列乐器不属于中国乐器的是( )。A.古筝 B.古琴 C.扬琴 D.竖琴
案例: 小美是初二的学生,学习成绩中等偏下,性格孤僻,在学校经常独来独往,放学
市场年利率为8%,指数年股息率为2%,当股票价格指数为1000点时,3个月后交割
代谢性酸中毒最突出的症状是A.呼吸加深加快,有烂苹果味 B.口唇苍白 C.呼
月末企业银行存款日记账余额为210000元,银行对账单余额为170000,经过未
最新回复
(
0
)