The magnetic field of the Sun operates on a 22 year cycle. It takes 11 years for the orientation of the field to flip between the northern and southern hemisphere.
The Solar and Heliospheric Observatory (SOHO) has been watching the Sun for almost 20 years. In that time it has seen solar activity ramp up and die down repeatedly. Its Extreme ultraviolet Imaging Telescope has taken images of the resulting waxing and waning of the Sun’s corona – its atmosphere – that are impossible to record from the ground.
Our atmosphere blocks more than 75% of ultraviolet radiation from reaching Earth’s surface, and extreme ultraviolet is entirely absorbed. To see it, spacecraft such as SOHO must be used.
The individual images in this composition show gas with a temperature of about 2 million degrees Celsius in the Sun’s atmosphere. This atmosphere, known as the corona after the Latin word for crown, extends millions of kilometers from the Sun.
The corona carries away the particles of the solar wind. If accelerated streams of particles reach Earth and strike our atmosphere, they can spark colorful displays of the aurora.
Image credit SOHO (ESA & NASA)
source ESA
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