Linked from
The 8 pages that link to Coronal heating problem, each with the reason it gives.
Solar coronaRelated: It captures the central puzzle of the corona’s extraordinary temperature.
Alfvén waveRelated: Dissipation of Alfvénic energy is one candidate source of the required heat.
Parker Solar ProbeRelated: Parker investigates processes that transfer energy into the corona.
HeliophysicsRelated: Its solution would explain the energy balance of the solar atmosphere.