An accommodating sun, Science News, February 28, 1970 –

This year’s eclipse [offers] an important opportunity for observation…. The temperature of the main body of the sun is about 6,000° Celsius, but the temperature in the corona goes up to millions of degrees. Some observers will seek to determine … the nature of the heating mechanism and the possible role of magnetic fields in keeping hot regions separated from cool ones.

Update

We still don’t know how the corona, the sun’s outer atmosphere, reaches such extreme temperatures. Theories suggest the sun’s magnetic field somehow shifts solar energy to the corona, more than 2,000 kilometers above the sun’s surface. Plasma tendrils erupting from near the sun’s surface might transfer energy to the corona in conjunction with magnetic field realignments (SN: 12/7/19, p. 14).

NASA’s Parker Solar Probe, launched in 2018, will measure the magnetic field from within 6 million kilometers of the sun’s surface (SN: 7/21/18, p. 12). Until then, a detailed infrared image of the corona taken during the 2017 solar eclipse could shed more light on the magnetic field.