| Abstract from DBPedia | The solar cycle, also known as the solar magnetic activity cycle, sunspot cycle, or Schwabe cycle, is a nearly periodic 11-year change in the Sun's activity measured in terms of variations in the number of observed sunspots on the Sun's surface. Over the period of a solar cycle, levels of solar radiation and ejection of solar material, the number and size of sunspots, solar flares, and coronal loops all exhibit a synchronized fluctuation from a period of minimum activity to a period of a maximum activity back to a period of minimum activity. The magnetic field of the Sun flips during each solar cycle, with the flip occurring when the solar cycle is near its maximum. After two solar cycles, the Sun's magnetic field returns to its original state, completing what is known as a Hale cycle. This cycle has been observed for centuries by changes in the Sun's appearance and by terrestrial phenomena such as aurora but was not clearly identified until 1843. Solar activity, driven by both the solar cycle and transient aperiodic processes, governs the environment of interplanetary space by creating space weather and impacting space- and ground-based technologies as well as the Earth's atmosphere and also possibly climate fluctuations on scales of centuries and longer. Understanding and predicting the solar cycle remains one of the grand challenges in astrophysics with major ramifications for space science and the understanding of magnetohydrodynamic phenomena elsewhere in the universe.太陽活動周期（たいようかつどうしゅうき、英: Solar cycle）は、太陽の活動（太陽放射のレベルや物質の放出等）や見かけ（太陽黒点の数や太陽フレア等）の周期的な変化である。約11年周期となる。太陽の見かけの変化やオーロラの変化として、数百年に渡って観測されてきた。 太陽の変化は、太陽から地球に達する放射の量を周期的に変化させ、宇宙天気、地球の天気や気候等の変化を引き起こす。 非周期的変動とともに、太陽変動の1つである。 内部の太陽流によって誘導される磁気流体力学的ダイナモ作用によって、太陽活動周期は以下の役割を担う。
* 太陽大気、コロナ、太陽風の形成
* 太陽光の調節
* 紫外線からX線までの短波長太陽放射の調節
* 太陽フレア、コロナ質量放出やその他の太陽爆発現象の調節
* 太陽系に入ってくる高エネルギー宇宙線の流れの間接的な調節 (Source: http://dbpedia.org/resource/Solar_cycle) |
