為什麼北極光南移了？

為什麼北極光南移了？
Why have the Northern Lights moved south?
By Victoria Gill
5 August 2010
Science reporter, BBC News
The Northern lights, it seems, have moved further south and have been visible from countries including Germany and Denmark. So what exactly is causing this spectacle? And how long will it last?
北極光似乎已進一步向南移動，並已能見到在國家包括德國和丹麥。那麼究竟是什麼造成這場面？和會持續多久？
A recent increase in solar activity is having an effect on Earth's magnetic field (blue) and the Northern Lights
太陽活動最近的增加對地球磁場（藍色）和北極光有一定影響
1. The Northern Lights or Aurora Borealis are caused by charged particles around the Earth being excited by the interaction between the Earth's magnetic field and the solar wind, a stream of particles and magnetic field from the Sun.
2. The solar wind's magnetic field can "break" Earth's magnetic field lines and drag the two ends away, creating "open" field lines. When the Sun is very active, as it has been recently, more of the Earth's magnetic field lines are broken.
3. These lines "snap back" into a continous loop around the Earth, producing an electric current that excites gas particles in our atmosphere, making them glow. When more of Earth's magnetic field lines are broken, this reconnection - and the glow it causes - occurs further from the poles.

The Northern Lights, or Aurora Borealis, are caused by charged gas particles - that flow away from the Sun as a "solar wind" - interacting with the Earth's magnetic field.

This solar wind has its own magnetic field, which can "drag away" the Earth's magnetic field lines, disconnecting them from our planet.

Eventually though, the field lines "snap back" into the continuous loop that exits one of the Earth's magnetic poles and re-enters at the other. This snapping back or "reconnection" means that particles that were in the solar wind are pushed into the Earth's atmosphere.

The charged particles "excite" gases in our atmosphere and make make them glow - just like gas in a fluorescent tube. The colours depend on the type of gas - a red or green glow is oxygen and the blue and purple colours are produced by nitrogen.
The spectacular Aurora Borealis are usually only visible in the far north
壯觀的北極光通常只能在遙遠的北方可見

The huge ejection of charged particles from the Sun on 3 August disconnected more of the Earth's magnetic field lines and when these snapped back to Earth the resulting auroras were visible much further south than usual.

Dr Colin Forsyth from the UCL's Mullard Space Science Laboratory explained that the boundary between "open" (or disconnected) field lines and the rest of the Earth's magnetic field is "where aurora are most likely to occur". And when more field lines are disconnected, that boundary moves south.

On Wednesday night stunning light displays were seen over parts of northern Europe, including Germany and Denmark, but so far scientists say there has not been "sufficient activity" over southern parts of the UK to produce a light show.

Professor Mike Kosch from Lancaster University said it was "possible but unlikely" that the Northern Lights would be visible from England on Thursday night.

He explained that the chances to view the results of the magnetic storms would be best in northern Scotland and northern parts of Europe. "They could be going on above our heads during the day, but we can't see them," he said.

The space storms can affect satellite communication systems, but satellite operators monitor the activity of the Sun to mitigate any potential problems.

The same phenomenon occurs around the southern magnetic pole and is known as the Aurora Australis or the southern polar lights.

http://www.bbc.co.uk/news/science-environment-10880852

太陽風暴來襲 北極光南移了
編譯中心綜合3日電
August 04, 2010 06:00 AM
世界新聞網
天文學者1日觀測到太陽表面發生巨大的噴發，在美國太空總署提供的這張太陽X射線影像中，右上方邊緣附近的暗弧就是太陽噴發時表面噴出的電漿細絲。較明亮部分是不相關的太陽閃焰。這次噴發的粒子3日或4日抵達地球時，可能產生強烈的極光。（美聯社）

科學家警告，在太陽表面發生大規模爆炸後，地球最快在3日可能會遭到一場劇烈太空風暴的襲擊，大量帶電粒子將衝往地球。過去僅能在北極圈附近看到極光，現因太陽風暴影響，包括美國緬因州、密西根州和加拿大南方地區，都可看到壯觀的「霓虹極光秀」。

英國每日電訊報報導，包括美國太空總署（NASA）太陽動態觀測衛星在內的多個衛星，曾在周末觀測到太陽表面發生巨大爆炸，震波向四周擴散。

全球天文學家都目擊到，在宛如地球大小的太陽黑子上方出現巨大太陽閃焰。這種又稱為日冕噴發（Coronal Mass Ejection）的爆發現象，將以太陽風暴的形式，越過9300萬英里的太空，直擊地球。

專家表示，噴發出來的強烈太陽風很可能在今天抵達地球，衝擊保護地球的磁場。報導說，同時也很可能在地球兩極產生強烈的極光。加拿大研究人員表示，目前很難預測太陽噴發所產生光焰的強度，及如何影響北極光，但加拿大人若有興趣的話，可以睡晚一些，說不定能看到天空出現紅紅綠綠的北極光。

科學家警告，如果這次是一場真正大型的太陽風暴，可能會摧毀地球衛星，並造成全球電力和通信系統中斷。科學家6月曾預測太陽閃焰活動可能在2013年達到高峰，屆時可能會嚴重干擾衛星通訊，甚至影響飛安或供應水電，造成嚴重災害。
http://www.worldjournal.com/view/full_news/8991604/article-%E5%A4%AA%E9%99%BD%E9%A2%A8%E6%9A%B4%E4%BE%86%E8%A5%B2-%E5%8C%97%E6%A5%B5%E5%85%89%E5%8D%97%E7%A7%BB%E4%BA%86?instance=in_bull

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