Primary cosmic rays

Japanese: 一次宇宙線 - いちじうちゅうせん（英語表記）primary cosmic ray

Cosmic rays that reach the Earth from space. A term used in contrast to secondary cosmic rays, which are produced by multiplication in the atmosphere. Their energies range from 10 ⁷ eV (electron volts) to 10 ²¹ eV. Primary cosmic rays are divided into galactic cosmic rays and solar cosmic rays. The former are produced in the galaxy and propagate through the space within the galaxy. The latter are produced by solar flares and propagate through interplanetary space.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

宇宙から地球に入射する宇宙線。大気中で増殖して生じる二次宇宙線に対比させた用語。そのエネルギーは 10⁷eV（電子ボルト）から 10²¹eVに及ぶ。一次宇宙線は銀河宇宙線と太陽宇宙線とに分けられる。前者は銀河系でつくられ，銀河系内の空間を伝搬する。後者は太陽のフレアで発生し惑星間空間を伝搬する。

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