page_title: Solar phenomena
section_title: Observation history
hierarchical_section_title: Solar phenomena / Observation history
caption_attribution_description: Original image description from the Deutsche Fotothek Astronomie &amp; Physik &amp; SonneIllustration of sunspots drawn by 17th-century German Jesuit scholar Athanasius Kircher
context_page_description: Solar phenomena are the natural phenomena occurring within the magnetically heated outer atmospheres in the Sun. These phenomena take many forms, including solar wind, radio wave flux, energy bursts such as solar flares, coronal mass ejection or solar eruptions, coronal heating and sunspots.
  These phenomena are apparently generated by a helical dynamo near the center of the Sun's mass that generates strong magnetic fields and a chaotic dynamo near the surface that generates smaller magnetic field fluctuations.
  The total sum of all solar fluctuations is referred to as solar variation. The collective effect of all solar variations within the Sun's gravitational field is referred to as space weather. A major weather component is the solar wind, a stream of plasma released from the Sun's upper atmosphere. It is responsible for the aurora, natural light displays in the sky in the Arctic and Antarctic. Space weather disturbances can cause solar storms on Earth, disrupting communications, as well as geomagnetic storms in Earth's magnetosphere and sudden ionospheric disturbances in the ionosphere. Variations in solar intensity also affect Earth's climate.
context_section_description: Solar activity and related events have been regularly recorded since the time of the Babylonians. Early records described solar eclipses, the corona and sunspots.
  Soon after the invention of telescopes, in the early 1600s, astronomers began observing the Sun. Thomas Harriot was the first to observe sunspots, in 1610. Observers confirmed the less-frequent sunspots and aurorae during the Maunder minimum.
  Solar spectrometry began in 1817. Rudolf Wolf gathered sunspot observations as far back as the 1755–1766 cycle. He established a relative sunspot number formulation (the Wolf or Zürich sunspot number) that became the standard measure. Around 1852, Sabine, Wolf, Gautier and von Lamont independently found a link between the solar cycle and geomagnetic activity.
  On 2 April 1845, Fizeau and Foucault first photographed the Sun. Photography assisted in the study of solar prominences, granulation, spectroscopy and solar eclipses.
  On 1 September 1859, Richard C. Carrington and separately R. Hodgson first observed a solar flare. Carrington and Gustav Spörer discovered that the Sun rotates at different rates at different latitudes, and that the outer layer must be fluid.
  In 1907–08, George Ellery Hale uncovered the Sun's magnetic cycle and the magnetic nature of sunspots. Hale and his colleagues later deduced Hale's polarity laws that described its magnetic field.
  Bernard Lyot's 1931 invention of the coronagraph allowed the corona to be studied in full daylight.
  The Sun was, until the 1990s, the only star whose surface had been resolved. Other major achievements included understanding of:
  X-ray-emitting loops (e.g., by Yohkoh)
  Corona and solar wind (e.g., by SoHO)
  Variance of solar brightness with level of activity, and verification of this effect in other solar-type stars (e.g., by ACRIM)
  The intense fibril state of the magnetic fields at the visible surface of a star like the Sun (e.g., by Hinode)
  The presence of magnetic fields of 0.5×10⁵ to 1×10⁵ gauss at the base of the conductive zone, presumably in some fibril form, inferred from the dynamics of rising azimuthal flux bundles.
  Low-level electron neutrino emission from the Sun's core.
  In the later twentieth century, satellites began observing the Sun, providing many insights. For example, modulation of solar luminosity by magnetically active regions was confirmed by satellite measurements of total solar irradiance (TSI) by the ACRIM1 experiment on the Solar Maximum Mission (launched in 1980).
caption: Illustration of sunspots drawn by 17th-century German Jesuit scholar Athanasius Kircher
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