科学美国人(翻译):太阳喷流在地球磁场中产生驻波 2019.03.12

cathy0301 2019-03-20 442 阅读
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Solar Jets Cause Standing Waves in Earth's Magnetic Field

太阳喷流在地球磁场中产生驻波

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, called plasma, from the Sun crash into it.

那奇怪的声音吗?它是地球的磁层——地球内部深处铁芯运动产生的磁场。磁层是一个盾牌,保护我们免受危险的宇宙射线。当来自太阳的带电粒子(称为等离子体)喷射到它上面时,它会像鼓一样振动。

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.

描述这一现象的理论是在20世纪70年代发展起来的。但是直到最近我们才有了观察它的工具。2007年,美国宇航局发射了五颗卫星来研究磁层,这一任务被称为次风暴期间的事件和宏观尺度相互作用的时间历史。

“We ended up making use of all five NASA THEMIS probes back very early in the mission, actually, when they were almost in a perfectly straight line.”Martin Archer, 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 impulsive hits our magnetosphere.”

“我们最终使用了NASA的所有5个忒弥斯探测器,实际上,在任务的早期,它们几乎是在一条完美的直线上。伦敦玛丽女王大学物理学和天文学教授马丁·阿彻说。“这真的是一个非常理想的尝试,以梳理到底发生了什么,当一些脉冲击中我们的磁层。”

“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 sent out ripples in all directions. Now, some of those will then travel towards the north and southern poles and get reflected back, and it's the interference of the original and reflected waves that allows the standing waves to form very much like the surface of a drum. And that gives it a very well defined frequency.”Archer’s team converted the signals collected by the probes into audio that we can hear. They published the discovery in the journal Nature Communications. [M.O. Archer et al, Direct observations of a surface eigenmode of the dayside magnetopause]

“所以基本上,在这个特殊事件中发生的事情非常简单。等离子体的喷射速度非常快,影响了磁极——这是我们磁层的边界。然后向四面八方扩散。现在,其中一些会向南北两极移动然后被反射回来,正是原始波和反射波的干涉使得驻波非常像鼓的表面。这就给了它一个很好的定义频率。阿彻的团队将探测器收集到的信号转换成我们能听到的音频。他们在《自然通讯》杂志上发表了这一发现。

“From the theory behind these drum-like oscillations, we know that they should have a big effect. They should penetrate 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.”

“从这些鼓状振荡背后的理论,我们知道它们应该有很大的影响。它们应该能穿透我们的磁屏蔽相当远,比如在有辐射带的区域内引起运动。当然,我们在磁场中看到了地面上的扰动,这告诉我们电离层也在移动,就像边界移动的方式一样,所以就像磁层的一边因为这种模式而振动。”

These events occur on a colossal 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.

这些事件发生在一个巨大的尺度上——磁层向外延伸大约是地球直径的10倍。阿彻的团队提出,未来的研究将着眼于基于地面的传感方法,以揭示更多关于磁层行为的信息。也许更好地理解我们的行星盾有一个重要的好处。

—Jim Daley

—来自Jim Daley


Solar Jets Cause Standing Waves in Earth's Magnetic Field

太阳喷流在地球磁场中产生驻波

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, called plasma, from the Sun crash into it.

那奇怪的声音吗?它是地球的磁层——地球内部深处铁芯运动产生的磁场。磁层是一个盾牌,保护我们免受危险的宇宙射线。当来自太阳的带电粒子(称为等离子体)喷射到它上面时,它会像鼓一样振动。

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.

描述这一现象的理论是在20世纪70年代发展起来的。但是直到最近我们才有了观察它的工具。2007年,美国宇航局发射了五颗卫星来研究磁层,这一任务被称为次风暴期间的事件和宏观尺度相互作用的时间历史。

“We ended up making use of all five NASA THEMIS probes back very early in the mission, actually, when they were almost in a perfectly straight line.”Martin Archer, 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 impulsive hits our magnetosphere.”

“我们最终使用了NASA的所有5个忒弥斯探测器,实际上,在任务的早期,它们几乎是在一条完美的直线上。伦敦玛丽女王大学物理学和天文学教授马丁·阿彻说。“这真的是一个非常理想的尝试,以梳理到底发生了什么,当一些脉冲击中我们的磁层。”

“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 sent out ripples in all directions. Now, some of those will then travel towards the north and southern poles and get reflected back, and it's the interference of the original and reflected waves that allows the standing waves to form very much like the surface of a drum. And that gives it a very well defined frequency.”Archer’s team converted the signals collected by the probes into audio that we can hear. They published the discovery in the journal Nature Communications. [M.O. Archer et al, Direct observations of a surface eigenmode of the dayside magnetopause]

“所以基本上,在这个特殊事件中发生的事情非常简单。等离子体的喷射速度非常快,影响了磁极——这是我们磁层的边界。然后向四面八方扩散。现在,其中一些会向南北两极移动然后被反射回来,正是原始波和反射波的干涉使得驻波非常像鼓的表面。这就给了它一个很好的定义频率。阿彻的团队将探测器收集到的信号转换成我们能听到的音频。他们在《自然通讯》杂志上发表了这一发现。

“From the theory behind these drum-like oscillations, we know that they should have a big effect. They should penetrate 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.”

“从这些鼓状振荡背后的理论,我们知道它们应该有很大的影响。它们应该能穿透我们的磁屏蔽相当远,比如在有辐射带的区域内引起运动。当然,我们在磁场中看到了地面上的扰动,这告诉我们电离层也在移动,就像边界移动的方式一样,所以就像磁层的一边因为这种模式而振动。”

These events occur on a colossal 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.

这些事件发生在一个巨大的尺度上——磁层向外延伸大约是地球直径的10倍。阿彻的团队提出,未来的研究将着眼于基于地面的传感方法,以揭示更多关于磁层行为的信息。也许更好地理解我们的行星盾有一个重要的好处。

—Jim Daley

—来自Jim Daley


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