The Solar Corona Observed in X-rays
- The cause of the solar wind is the pressure expansion of the very hot (million degrees Kelvin) solar corona.
- The high temperature causes the corona to emit X-rays.
- Images made by orbiting X-ray telescopes show the solar corona has a high degree of spatial structure, organized by magnetic fields.
- Within closed field coronal loops, these effectively hold back the coronal expansion.
- But along radially oriented, open-field regions the wind flows rapidly outward, leading to a relative reduction of the plasma density that appears as a relatively dark "coronal hole".