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
2015-04-24
65
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 magnetosphere, 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 earthward 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. Excited 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 the fusion of atoms.
The word "undergo" in Paragraph 3 most probably means______.
选项
A、endure
B、encounter
C、experience
D、confront
答案
C
解析
语义题。根据题干信息定位到原文第三段第三句。undergo意为“经历,遭受”,与选项C对应。故答案为C。
转载请注明原文地址:https://kaotiyun.com/show/NwLO777K
0
考博英语
相关试题推荐
Britishcancerresearchershavefoundthatchildhoodleukaemiaiscausedbyaninfection,andclustersofcasesaroundindustria
ThestrangestweatheroflastyearwaspossiblynotonEarth,butontheSun.Every11years【C1】______theSungoesthroughacyc
CrossingWesleyanUniversity’scampususuallyrequireswalkingovercolorfulmessageschalkedontheground.Theycanbeasinno
BeforehighschoolteacherKimberlyRughgotdowntobusinessatthestartofarecentschoolweek,shejokedwithherstudents
BeforehighschoolteacherKimberlyRughgotdowntobusinessatthestartofarecentschoolweek,shejokedwithherstudents
Amazonhasgivenintopublisherpressureandagreedtoabandontheir$9.99pricepointfore-Books.PuNisherMacmillanfelt
ThismonthSingaporepassedabillthatwouldgivelegalteethtothemoralobligationtosupportone’sparents.CalledtheMai
______ofhalf-starvingwolveswereroamingthesnow-coveredcountryside.
Inthewarmanychildrenwere______fromthecitiestocountryside.
随机试题
将5枚相同的纪念邮票和8张相同的明信片作为礼品送给甲、乙两名学生,要确保礼品全部分完且每人至少有一件,不同的分法有()。
Tyger!Tyger!burningbrightIntheforestsofthenight,WhatimmortalhandoreyeCouldframethyfearfulsymmetry?Questio
患者,男性,24岁,冬春季节上腹痛发作已有4年。近半个月来上腹痛加重,伴反酸及饥饿痛,并有半夜痛,痛醒后进食使疼痛缓解。1小时前突然发作上腹部刀割样剧痛,大汗淋漓,面色苍白,腹痛迅速蔓延至全腹而来院急诊。首选用哪项检查来协助作出诊断
A.咳喘无力,气短懒言B.干咳少痰,颧红潮热C.干咳无痰,鼻燥咽干D.咳嗽痰多,色白而黏E.咳嗽咯痰,发热恶寒肺气虚证常见的症状是()。
海关对()具有行政裁定权。
关于公司制期货交易所的独立董事和董事会秘书,下列说法正确的有(),
数学中学到的逻辑推理规则,有利于物理问题的解决,这属于()。
一次竞赛共有10道题目,答对前一道才能作答后一道,下一题的得分均比上题多2分,满分是100分。某人若要保证总分在80以上,每题的平均分至少为()?
设总体X的方差为1,根据来自X的容量为100的简单随机样本,测得样本均值为5,则X的数学期望的置信度近似等于0.95的置信区间为______.
Youcandrinkwinethere.Youcanseeafilmthere.
最新回复
(
0
)