The solar corona is the outermost part of the solar atmosphere. Due to its low density, scientists usually observe the corona during the solar eclipse or by ultra-violet imaging in space (see Figure 1). One may wonder that the corona should be cooler than the surface since the core, where nuclear fusion undergoes, is the hottest. However, the temperature of the solar atmosphere increases drastically below the corona (see Figure 2). The corona is actually filled with million-degree and highly-ionized plasma.
The heating of the solar corona is one of the major mysteries
Written on October 24th, 2021 by Yingjie Zhu