The Mysterious Origin of the Northern Lights 北极光的神秘来源

2023-09-07 05:27:28
时代英语·高三 2023年3期
关键词:豪斯北极光极光

The aurora borealis, or Northern Lights, could easily be described as Earths greatest light show. A phenomenon thats exclusive to the higher latitudes has had scientists in awe and wonder for centuries.

A group of physicists from the University of Iowa in the US have proven that the “most brilliant auroras are produced by powerful electromagnetic waves during geomagnetic storms,” according to a study.

The study shows that these phenomena, also known as Alfvén waves, accelerate electrons toward Earth, causing the particles to produce the light show we know as the Northern Lights.

“Measurements revealed this small population of electrons undergoes ‘resonant acceleration by the Alfvén waves electric field, similar to a surfer catching a wave and being continually accelerated as the surfer moves along with the wave,” said Greg Howes, associate professor in the Department of Physics and Astronomy at the University of Iowa and co-author of the study.

This idea of electrons “surfing” on the electric field is a theory first introduced in 1946 by a Soviet physicist, Lev Landau, that was named Landau damping. His theory has now been proven.

北極光经常被描述为地球上最盛大的“灯光秀”。几个世纪以来,这种高纬度地区独有的现象让科学家们大为敬畏和惊叹。

根据一项研究,美国艾奥瓦大学的一群物理学家已证实“这绝妙的极光是由地磁暴期间强大的电磁波所产生”。

研究表明,这些现象也被称为“阿尔文波”,它们可以使电子加速向地球移动,导致粒子产生我们所了解的北极光。

“测量表明,这一小群电子受到阿尔文波电场的‘共振加速,这类似于冲浪者抓住一个浪潮,并随着海浪的移动而不断加速。”艾奥瓦大学物理与天文学系副教授格雷格·豪斯表示,他是该研究的合著者。

1946年,苏联物理学家列夫·兰道首次提出电子在电场上“冲浪”的理论,并将其命名为朗道阻尼,他的理论现已得到证实。

Recreating the Northern Lights

Scientists have understood for decades how the aurora most likely is created, but they have been able to simulate it in recent years, for the first time, in a lab at the Large Plasma Device (LPD) in UCLAs Basic Plasma Science Facility in the US.

Scientists used a 20-meter-long vacuum chamber to recreate Earths magnetic field using the powerful magnetic field coils on UCLAs LPD. Inside the chamber, scientists generated a plasma similar to what exists in space near the Earth.

“Using a specially designed antenna, we launched Alfvén waves down the machine, much like shaking a garden hose up and down quickly, and watching the wave travel along the hose,” said Howes. As they began to experience the electrons “surfing” along the wave, they used another specialized instrument to measure how those electrons were gaining energy from the wave.

Although the experiment didnt recreate the colorful shimmer we see in the sky, “our measurements in the laboratory clearly agreed with predictions from computer simulations and mathematical calculations, proving that electrons surfing on Alfvén waves can accelerate the electrons (up to speeds of 45 million mph) that cause the aurora,” said Howes.

“These experiments let us make the key measurements that show that the space measurements and theory do, indeed, explain a major way in which the auroras are created,” said Craig Kletzing, the study co-author.

重现北极光

几十年来,科学家们已经了解极光最有可能产生的原因。但最近几年他们才在美国加州大学洛杉矶分校的基础等离子体科学设施实验室的大型等离子体装置上第一次模拟出极光。

科学家们利用加州大学洛杉矶分校的大型等离子体装置上强大的磁场线圈,用一个20米长的真空室重现地球磁场。在这个真空室内,科学家们制造出一种类似于地球附近空间中存在的等离子体。

豪斯说:“我们使用一种特殊设计的天线,让阿尔文波沿着机器向下波动,就像快速地上下摇动花园软管那样,然后观察波浪沿着软管传播。”当他们感受到电子沿着波“冲浪”时,便使用另一种专门的仪器来测量那些电子是如何从波中获得能量的。

尽管实验没有重现我们在天空中看到的彩色微光,但豪斯表示:“我们在实验室中的测量结果与通过计算机模拟和数学计算得出的预测结果明显一致,证明电子在阿尔文波上‘冲浪可以使电子加速(速度高达4500万英里/时,约7242万千米/时),从而产生极光。”

“这些实验帮助我们进行了关键的测量,由此表明空间测量和理论确实解释了极光产生的主要方式。”该研究的合著者克雷格·克莱津说道。

Many space scientists were ecstatic to hear the news. “I was tremendously excited! It is a very rare thing to see a laboratory experiment that validates a theory or model concerning the space environment,” said Patrick Koehn, a scientist in the Heliophysics Division of NASA. “Space is simply too big to easily simulate in the lab.”

“The electron acceleration mechanism verified by this project is at work elsewhere in the solar system, so it will find many applications in space physics. It will be of use in space weather forecasting as well,” Koehn said.

A long way to go

The theory of how the aurora is created has been proven, but theres still a long way to go in forecasting how strong each storm will be.

“Predicting how strong a particular geomagnetic storm will be, based on observations of the Sun and measurements from spacecraft between the Earth and the Sun, remains an unsolved challenge,” said Howes.

“We have established the link of electrons surfing on Alfvén waves about 10,000 miles above the Earths surface, and now we must learn how to predict the strength of those Alfvén waves using spacecraft observations,” he added.

很多太空科學家听到这个消息时都欣喜若狂。美国宇航局太阳物理学部门的科学家帕特里克·科恩表示:“我兴奋极了!通过实验室的实验验证有关太空环境的理论或模型是非常罕见的。太空明显太庞大,不太容易在实验室中进行模拟。”

“该项目验证的电子加速机制在太阳系的其他地方也在发挥作用,因此它将在空间物理学中非常有用。它也将用于太空天气预报。”科恩说。

未来的路还很长

极光如何形成的理论已经被证实,但要预测每次风暴的强度还有很长的路要走。

豪斯表示:“根据对太阳的观测和对地球和太阳之间航天器的测量,预测特定的磁风暴的强度仍然是一个悬而未决的挑战。”

“我们在离地球表面一万英里的地方搭建了电子在阿尔文波上‘冲浪的线路,现在我们必须学习如何通过航天器的观测结果来预测阿尔文波的强度。”他补充道。

Word Bank

exclusive /?k'sklu?s?v/ adj. 专有的;独有的

accelerate /?k'sel?re?t/ v. 加速;加快

simulate /'s?mjule?t/ v. 模拟

validate /'v?l?de?t/ v. 证实;确认

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