The Sun--Introduction and Links

    The first four sections (below) stress processes associated with sunspots, intensely magnetic regions on the Sun, whose number rises and falls in an irregular cycle of about 11 years. Near sunspots violent eruptions tend to occur, sending earthward fast plasma clouds ("Coronal Mass Ejections") and sometimes high energy ions and electrons.

16. The Sun

      16H. History: 1843--Heinrich Schwabe discovers the sunspot cycle.

16a. Discovery of Sunspot Cycle
16b. Discovery of Solar Flares

    The next four sections involve the solar corona, the Sun's extremely hot outermost atmosphere, still a puzzle to scientists. Solar gravity cannot hold such a hot plasma, and it expands forcibly in all directions as the "solar wind," responsible for most phenomena in the Earth's magnetosphere. The solar wind also draws out of the Sun magnetic field lines, producing the interplanetary magnetic field (IMF), and a section here describes how the IMF is shaped by the solar wind:

17. The Sun's Corona
18. The Solar Wind
      18A. Drawing Interplanetary Magnetic Field Lines.
      18H. History: 1959, 1961--First direct observations of the solar wind.

    In addition, one section is devoted to the high-energy particles ejected by solar flares, particles which could pose a hazard to interplanetary travelers:

35. Solar Energetic Particles

    However... "Exploration" also has two "sister sites," each of which has sections devoted to the Sun. Some material overlaps, but mostly each site covers different aspects. The section you are reading now is meant for users interested in a more complete picture, with links to relevant parts of those other sites.

"The Great Magnet, the Earth" is a historical discussion of the Earth's magnetism, originating in its central core. For a long time, the source of that magnetism was a mystery. What convinced scientists that a "dynamo mechanism" was responsible was evidence coming from sunspots, which are intensely magnetic. This led to a theory of the Sun's magnetism which, although now recognized as crude, is still of interest. The sections on this are:

The Sun's magnetic cycle
The Dynamo Process
The Self-Sustaining Dynamo in the Earth's Core
                (The 2nd half of that section discusses the Sun)

And in more detail, the sections on the Sun in a long historical review
"Sunspot Magnetism and the Geomagnetic Dynamo"

"From Stargazers to Starships", the 3rd site, is a large course (with some math) covering wide areas in astronomy, physics and space exploration. It includes a collection of web pages on the Sun, linked from an introductory section. Most of those pages use the Sun mainly to introduce areas of physics having some connection to it, such as weather and climate, or spectral lines and electromagnetic waves in different ranges of wavelength. One section describes x-ray emissions from the Sun:

S-6.     Seeing the Sun in a New Light

    This collection supplements the above material by discussing the Sun's energy source, nuclear fusion, with the attendant question of what happens when the Sun's fuel runs out. All this involves nuclear physics, so sections on nuclear energy and nuclear weapons were also added, as was an overview of the history of the study of atoms and nuclei.

    Even though the Sun apparently will not end its career as a black hole, one interesting object of this sort was also covered, namely the recently observed black hole at the center of our galaxy.

The sections on those topics are:

S-7.     The Energy of the Sun

and related to it:

LS-7A     The Discovery of Atoms and Nuclei
           (A very quick overview of the relevant history.)
S-7A     The Black Hole at the Center of our Galaxy
S-8.     Nuclear Power
S-9.     Nuclear Weapons