| The Sun radiates plasmas made of protons and electrons.
The radiation creates plasma currents and the thin, high-speed current
is called the solar wind. While the solar wind streams change their
speed depending on the solar activities, the Earth is normally protected
from them by terrestrial magnetic fields. When the strong solar wind
blows, a part of the streams reach the Arctic and Antarctic airspace
along the magnetic lines, plasmas hit atmospheric components and make
them emit light: Nitrogen molecules in blue and oxygen in yellow,
green and red. The mechanism of aurora is the same as those of fluorescent
lamps and neon signs. A donut area where plasmas flow in quantity and luminous aurora are observed is called the aurora zone. Aurora can be seen in Japan in rare cases. |
