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Scientists record breach in magnetic field

Artwork: The Earth's magnetosphere protects the planet from a continuous flow of cosmic radiation

Scientists have recorded the events that unfolded after the Earth's magnetic shield was breached.

Openings in the planet's magnetic field are not uncommon, but it is rarer to get the opportunity to gather data while such an event is in progress.

A cosmic ray monitoring facility recorded a burst of cosmic rays associated with the opening.

The magnetic field breach was the result of charged particles from the Sun striking the Earth at high speed.

The GRAPES-3 muon telescope located at the Cosmic Ray Laboratory (CRL) in Ooty, southern India, recorded a burst of galactic cosmic rays of about 20 gigaelectronvolts (GeV) on 22 June 2015.

"In this case the magnetic field was breached for only two hours and then returned back to normal. The magnetic field strength reduced only by 2%," Dr Sunil Gupta, lead scientist at the CRL told the BBC.

Earth's magnetic shield, or magnetosphere, extends over a radius of a million kilometres. It protects the planet's biosphere from the continuous flow of solar and other cosmic radiation.

The Sun periodically ejects vast clouds of charged particles into space in events known as coronal mass ejections (CMEs). Each one can contain a billion tonnes of charged gas, or plasma.

The giant cloud of plasma ejected from the solar corona in 2015 caused massive compression of the Earth's magnetosphere and triggered a severe geomagnetic storm. In turn, this generated aurora borealis (northern lights), and radio signal blackouts in many high latitude countries.

Numerical simulations performed by the GRAPES-3 team on this event indicate that the Earth's magnetic shield temporarily opened up in response to the incoming solar plasma, allowing the lower energy galactic cosmic ray particles to enter our atmosphere.

Dr Gupta said that the CRL's measurements of the two-hour breach "gives us much more comprehensive information over a much larger region of space than the satellite based instruments".

The GRAPES-3 Muon telescope's combination of a large area and directional measurement enabled the accidental observations.

"We have been aware of impacts on the Earth from solar activity for a long time through the discovery of CMEs, but the Indian study adds a new element to this endeavour, with detailed analysis of a major particle event during the arrival of a particular cloud," Dr Richard Harrison, head of space physics and chief scientist at the Rutherford Appleton Laboratory in Oxfordshire, UK, told BBC News.

A major event could occur any time with potentially significant impacts on human infrastructure. As such, there are ongoing efforts to improve the prediction of this so-called space weather.

"They can short circuit power supplies such as high voltage transformers which provide power to our cities, disrupt communication satellites and therefore will affect, for example, internet, mobile phones and just about anything that uses electricity," said Dr Harrison.

In addition, he said, a major solar storm could also threaten humans in space, with the potential for damage to or the loss of spacecraft - although such events are expected to be rare.

Scientists at CRL hope that the vast amount of data now available would enable them to better predict such events and take preventative measures. But the real challenge is to devise appropriate electronic hardware that can issue a reliable alert, Dr Gupta said.


回复 NanouBao:

科学家记录了磁场上的缝隙

插图:地球磁场保护地球免受持续性宇宙射线流的冲击

科学家已经记录了地球磁场被击穿后所发生的事件。

在地球磁场上开个口子已经很不寻常了,然而趁地球磁场被打开这样一个机会对其进行数据收集更加不寻常。

一台宇宙射线监控仪记录一个与地球磁场打开有关的宇宙射线大爆发。

这次磁场破碎是来自太阳的高速带电粒子流冲击地球(磁场)的结果。

位于印度南方O地的宇宙射线实验室中的Grapes-3 μ望远镜在2015年6月22日记录(电荷数量级)约为200亿电子伏(gigaelectronvolt,一个衡量电荷数的物理量单位,中文是十亿电子伏,符号GeV,giga-作数量级表十亿,等于billion)的超大宇宙射线大爆发。

CRL学术负责人SG博士告诉BBC称在这次事件中,地球磁场出现的缝隙维持了约两小时而之后就恢复正常了。磁场强度仅被削弱了约2%。

地球磁场又称磁圈,覆盖范围为半径约100万千米的球体。它保护地球生物圈免受太阳或其他宇宙放射源发出的粒子流的冲击。

太阳向宇宙周期性抛射海量的带电粒子团(cloud直译云)的事件被称为日冕物质抛射(CME)。每次抛射出的粒子团都能包含约10亿吨的电离气体或等离子体。

2015年从太阳日冕射出的巨大等离子体团对地球磁场造成了巨大压力并触发了一次严重了地磁风暴。因此(in turn直译反之,但此处上下文是承接关系,故翻译为因此)这导致了北极极光(aurora borealis首字母小写时作北极极光等于northern lights,首字母大写时作北冕座)以及众多高纬国家的通讯信号中断。

Grapes-3团队对此次事件进行的数字模拟重演表明地球磁场因(in response to直译对什么做出响应)太阳粒子流冲击而短暂开放,使得低能银河宇宙射线粒子进入地球大气。

G博士称CRL对这次维持两小时长的(磁场)破碎的观测为学界带来的关于如此巨大宇宙空间的复杂信息比天基设备获得的更多。

Grapes-3μ望远镜将大范围和直接观测联合使得这次偶发性观测成为可能。

英国牛津的卢瑟福-阿普顿实验室太空物理学权威和首席科学家RH博士告诉BBC新闻称,自CME发现以来相当长的时间内学界就认识到了太阳活动对地球的影响,但这项印度研究以在一个特定粒子团抵达时对大量粒子(冲击)事件进行详细分析的方式为这次努力添加了新要素。

对人类设备有潜在显著冲击的大(粒子冲击)事件随时可能发生。因此,学界正努力提升对这种被称为太空天气事件的预测能力。

H博士称它们(指高能粒子团)能使为城市供电的高压输电器等供电设备短路、瓦解通讯卫星从而影响互联网和手机等信号、以及任何电子设备。

他该补充道一次大型太阳风暴也能以潜在伤害的形式威胁宇航员,或者造成太空飞行器报废,尽管这些事件预期非常罕见。

CRL的科学家希望这些目前可用的大量数据能使他们更好地预测此类事件并采取预防性措施。但G博士称真实的挑战是设计恰当的电子硬件以发布可靠的警报。


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