The answer first
The photosphere is about 5,800 K, while coronal plasma commonly exceeds a million kelvin. Magnetic fields provide the energy reservoir; waves and reconnection are the leading transport and release mechanisms.
Different regions may be heated differently. Coronal holes, active loops, and the quiet corona do not require one identical recipe.
The idea that changes the view
Above the Sun’s visible surface, thinner plasma becomes dramatically hotter.
What most explanations leave out
Temperature is average particle energy, not total heat. The corona is extraordinarily hot but extremely tenuous.
Evidence and named signals
- Spectral lines diagnose temperature and density.
- SDO resolves magnetized coronal structures.
- Parker Solar Probe samples the young solar wind.
What remains uncertain
The relative contribution of wave damping and small reconnection events remains region-dependent and actively studied.
Why it matters—or what you can observe
Coronal heating is tied to the origin of the solar wind and the space weather that reaches Earth.
Related StarPixels video · 0:37
Why the Sun’s Corona Is Hotter Than Its Surface
Move away from the Sun’s visible surface and the temperature rises by orders of magnitude.
Open the video companionFurther reading and primary sources
- NASA Parker Solar ProbeSource checked 2026-07-16
- NASA SDOSource checked 2026-07-16
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