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科学美国人60秒 SSS 太阳射流在地球磁场中产生驻波

时间:2019-12-16 07:03:21

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This is Scientific American's 60-second Science, I'm Jim Daley.

(Audio of magnetosphere)

That strange sound? It's Earth's magnetosphere—the magnetic field created by the movement of the iron core deep within the planet. The magnetosphere is a shield, protecting us from dangerous cosmic rays. And it vibrates like a drum when jets of charged particles from the sun, called plasma1, crash into it.

The theory describing this phenomenon was developed in the 1970s. But it wasn't until recently that we had the tools to observe it. In 2007 NASA launched five satellites to study the magnetosphere, in a mission called Time History of Events and Macroscale Interactions during Substorms, or THEMIS.

"We ended up making use of all five NASA THEMIS probes back very early in the mission, actually, when they were almost in a perfectly2 straight line."

Martin Archer3, professor of physics and astronomy at Queen Mary University of London.

"And that was really ideal for trying to tease apart exactly what happens when something impulsive4 hits our magnetosphere."

"So basically, what happened in this particular event is really quite simple. You had a jet of plasma traveling very fast that impacted on the magnetopoles—that's the boundary of our magnetosphere. That then s?ent out ripples5 in all directions. Now, some of those will then travel toward the north and southern poles and get reflected back, and it's the interference of the original and reflected waves that allows the standing6 waves to form very much like the surface of a drum. And that gives it a very well-defined frequency."

Archer's team c?onverted the signals collected by the probes into audio that we can hear. They published the discovery in the journal Nature Communications.

"From the theory behind these drumlike oscillations, we know that they should have a big effect. They should penetrate7 our magnetic shield quite far, causing motions within regions where there are the radiation belts, for instance. Certainly, we saw perturbations on the ground in the magnetic field and that tells us that the ionosphere is moving as well, just in the same way as the boundary is, so it's like one side of the magnetosphere is just all ringing because of this mode."

These events occur on a colossal8 scale—the magnetosphere extends outward about 10 times the diameter of the earth. Archer's team has proposed that future studies look into ground-based sensing methods that can reveal more about the magnetosphere's behavior. Perhaps there's an important upside in better understanding our planetary shield.

Thanks for listening for Scientific American — 60-Second Science. I'm Jim Daley.


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1 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。
2 perfectly 8Mzxb     
adv.完美地,无可非议地,彻底地
参考例句:
  • The witnesses were each perfectly certain of what they said.证人们个个对自己所说的话十分肯定。
  • Everything that we're doing is all perfectly above board.我们做的每件事情都是光明正大的。
3 archer KVxzP     
n.射手,弓箭手
参考例句:
  • The archer strung his bow and aimed an arrow at the target.弓箭手拉紧弓弦将箭瞄准靶子。
  • The archer's shot was a perfect bull's-eye.射手的那一箭正中靶心。
4 impulsive M9zxc     
adj.冲动的,刺激的;有推动力的
参考例句:
  • She is impulsive in her actions.她的行为常出于冲动。
  • He was neither an impulsive nor an emotional man,but a very honest and sincere one.他不是个一冲动就鲁莽行事的人,也不多愁善感.他为人十分正直、诚恳。
5 ripples 10e54c54305aebf3deca20a1472f4b96     
逐渐扩散的感觉( ripple的名词复数 )
参考例句:
  • The moon danced on the ripples. 月亮在涟漪上舞动。
  • The sea leaves ripples on the sand. 海水在沙滩上留下了波痕。
6 standing 2hCzgo     
n.持续,地位;adj.永久的,不动的,直立的,不流动的
参考例句:
  • After the earthquake only a few houses were left standing.地震过后只有几幢房屋还立着。
  • They're standing out against any change in the law.他们坚决反对对法律做任何修改。
7 penetrate juSyv     
v.透(渗)入;刺入,刺穿;洞察,了解
参考例句:
  • Western ideas penetrate slowly through the East.西方观念逐渐传入东方。
  • The sunshine could not penetrate where the trees were thickest.阳光不能透入树木最浓密的地方。
8 colossal sbwyJ     
adj.异常的,庞大的
参考例句:
  • There has been a colossal waste of public money.一直存在巨大的公款浪费。
  • Some of the tall buildings in that city are colossal.那座城市里的一些高层建筑很庞大。

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