This morning the UK will be treated to a partial solar eclipse, when a chunk of the Sun will gradually disappear in the shadow of the Moon. But a spectacular total solar eclipse will sweep across the Arctic, Mongolia and China, in which the Sun will be completely blotted out by the Moon.

A total solar eclipse is like no other sight on Earth. As the Sun disappears, a ring of fire appears around the Moon’s shadow. This is the outer atmosphere of the Sun, its corona, which, at over a million degrees celsius, is far hotter than the surface of the Sun at a mere 5,000C (9,000F), for reasons that are not entirely understood.

Solar eclipses first revealed the solar corona and its incredible heat. This helped lead to the discovery of the solar wind exactly 50 years ago, by Eugene Parker, of the University of Chicago.

The solar wind is a gradual extension of the corona escaping out into space at speeds reaching up to 3,600,000km/h (2,240,000mph) in a flow of electrically charged gas.

Times Archive, 1927: The eclipse

The spectacle surpassed anything our imaginations had shaped

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• Letter: The eclipse

• Letter: The eclipse

According to Parker, the beginning of the wind is best seen in a total solar eclipse, in which fingers of the Sun’s corona can be seen reaching out into space. However, the solar wind was a highly controversial idea, and two science journals rejected his research paper. In the 1960s, though, satellites confirmed the existence of the wind and opened the door to a new field of astrophysics.

The solar wind is of particular interest because of the way it collides with the Earth’s upper atmosphere, and causes magnetic storms that can knock out satellites or power grids on the ground and generate the amazing lights of the auroras.