Aurora

Japanese: オーロラ

Originally, it was the English pronunciation of Aurora, the goddess of dawn in Roman mythology. By extension, it is a luminous phenomenon in the atmosphere that appears mainly in the sky at high latitudes. It is also called the aurora. Its appearance can be a radially opening (corona-like), a swaying (curtain-like), or an active (flame-like), and it is often yellow to green in color, but also red, blue, and other brightnesses. It is caused by a flow of charged particles (plasma) coming from the sun penetrating the magnetic cavity of the Earth and colliding with air molecules in the ionosphere, causing them to glow. It is based on the same principle as the glow of a neon tube. It always appears with a magnetic storm, and increases and decreases in parallel with the 11-year cycle of sunspots. There are two types of plasma flows: those in which the Earth's magnetic field causes plasma flows to concentrate in the polar regions, causing the E layer in high latitudes (100 km above ground) to glow; and those in which the plasma flows form a current system that surrounds the equator in the upper atmosphere several hundred kilometers above, causing the F layer (200-400 km) to glow.

Source : Heibonsha Encyclopedia About MyPedia Information

Japanese:

元来はローマ神話の曙(あけぼの)の女神アウロラの英語読み。転じて主として高緯度地方の上空に現れる大気の発光現象。極光とも。外観は，放射状に開く〈コロナ状〉，ゆれ動く〈幕状〉，活動の激しい〈炎状〉など，色は黄〜緑が多く，そのほか赤，青など，明るさもさまざまである。太陽から飛んでくる荷電粒子流（プラズマ）が地球の磁気空洞のなかに侵入し，電離層中の空気の分子に衝突して発光させるもの。ネオン管の発光と同様の原理による。必ず磁気あらしに伴って出現，太陽黒点の11年周期に平行して増減する。プラズマ流が地球磁場のため極地方に集中させられ高緯度地方のE層付近（地上100km）を発光させるものと，プラズマ流がいったん数百kmの超高層大気中に赤道を取り巻くような電流系を形成，これが原因となってF層付近（200〜400km）を発光させるものの２種類に分かれる。

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