18/19 第二期 神秘莫測的極光


每當人類見到係天空中閃閃發光既極光,都會衍生出好多唔同既神話故事。例如維京人就認為極光係 通向佢地神靈之家Asgard既橋樑🛤。而係芬蘭,就有故事講述天使😇同魔鬼😈係天空上面戰鬥,天 使創造左令人眼花既燈光去騷擾敵人,咁就形成咗我地睇到既北極光啦。而土著格陵蘭人就認為,夜 空中既極光係係分娩中死亡bb👼🏻既舞蹈精神💃。幾個世紀以黎極光都令好多人著迷😍,但呢啲令人驚 嘆既燈光表演究竟係係邊度黎?同埋佢哋到底係點樣形成呢?🤔

極光嘅英文名係Aurora🌌,由第一個觀察到極光嘅天文學家🔭,伽利略命名。北極光Aurora Borealis ,拉丁語嘅意思係指北方嘅黎明🌅。而係南極發生嘅極光就被稱為Aurora Australis。

極光係由太陽發射出黎既質子同電子既質量引起既🌞。一啲穩定既氣流被稱為太陽風🌪,而一啲大規 模既噴發就被稱為日冕大量拋射(CME)。兩者都含有高度電離既粒子(質子和電子),稱為等離子 體😎。太陽射出既等離子體會同地球既磁場碰撞🌏。係呢個時候磁場就可以保護地球免受太陽風既影 響💪。當CME直接擊中地球等離子體,等離子體會受磁層的磁場綫引導到南北兩極⛄。擁有高能量同溫 度既等離子體會加熱高層大氣入邊既氧同埋氮🔥。呢啲粒子就會被激發並發出光子(光既粒子),產生 極光既顏色😍。氧氣負責產生綠色同埋紅色既極光,而氮氣則負責產生藍色同深紅色極光。黃綠色既極 光通常可以係地球上空大概60英里見到😳,而稀有既紅色極光就會出現係地球上空既200英里😋。

Strong Thermal Emission Velocity Enhancement (STEVE),係幾年前發現既一種新型極光 😍。第一次記錄到STEVE既係由公民科學家同埋業餘愛好者組成既Facebook粉絲專頁Alberta Aurora Chasers。 STEVE同傳統極光唔同🙈,並唔係綠色而係神祕既紫色🌌,發生係比正常極光(100英里以上)高既大氣層,以 及係赤道60度以上🌏。 不過STEVE到而家仍然有好多未知之處🤔,所以NASA正同Alberta Aurora Chasers同 埋其他極光愛好者合作,希望可以更加了解STEVE😎。


撰文:芮愷程, 譚健朗

Mysterious Aurora

Even though we might not be able to see Aurora or the Polar Lights here in Hong Kong. However, Aurora had attracted the attention of humankind for many centuries. The Aurora had inspired tales and myths for centuries when human beings first see it shimmer across the sky. The Vikings thought the aurora are the bridges to Asgard, the home of their gods. While, in Finland, some tales spoke of Angels fighting off devils in the sky, which created these dazzling displays of lights. Indigenous Greenlanders believed that the lights in the night sky are the dancing spirits of children who died in childbirth. Aurora had fascinated us for centuries, but where are these breathtaking light shows come from? And how are they formed?

Aurora is first named by Italian Astronomer Galileo Galilei when he first observed it. He coined the term Aurora Borealis. Which in Latin means Dawn of the North. And the southern lights occur in the southern atmosphere is called Aurora Australis.

Aurora is usually caused by the mass of protons and electrons emitted by the Sun. Some came in steady streams are called Solar Wind, while some that massive eruptions are called Coronal Mass Ejections (CME). Both contain highly ionized particles (Protons and electrons), which called Plasma. The plasma ejected by the Sun then collide with the magnetosphere of the Earth. The magnetosphere protects the Earth from Solar Winds and sometime CME that hits the planet directly. The plasma stresses the Earth’s magnetic fields. The plasma travels along the Earth’s magnetic stripe and towards the poles of the planet. The high energy and heat plasma heat up the particles such as Oxygen and Nitrogen in the upper atmosphere. The Oxygen and Nitrogen particles are excited and emit photons (light particles) that creates the dazzling colours of the polar lights. Excited Oxygens are responsible for producing green and red polar lights, while excited Nitrogens are responsible for producing blue and deep red polar lights. Yellow-greenish colour polar lights are usually be seen 60 miles above the Earth, while the rarer red aurora happens at 200 miles above Earth.

Strong Thermal Emission Velocity Enhancement (STEVE), is a new type of aurora discovered just a few years ago. The first recorded encounter of STEVE is by citizen scientist and amateur astronomers that formed a Facebook group named Alberta Aurora Chasers. STEVE is a purple colour stripe that occurs higher up in the atmosphere than normal aurora (100 miles up). And 60 degrees above the equator. There is still a lot unknown about STEVE. NASA is currently collaborating with aurora chasers and other aurora lovers to find out more about STEVE.
More about Polar Lights:

Author: Leo Tam and Jojo Yui

(Photo was taken from…/northern-lights-promise/)