The solar coronal heating problem
Determine which physical mechanisms heat the solar corona to millions of kelvin above a photosphere of about 5,800 K, and in what proportion, using public spacecraft data and simulations.
Cite
@misc{cairn-solar-coronal-heating,
title = {The solar coronal heating problem},
author = {{Cairn Commons contributors}},
howpublished = {\url{https://cairn-commons.com/problems/solar-coronal-heating}},
year = {2026},
note = {Open problem on Cairn Commons, CC BY 4.0. Accessed 2026-09-28}
} Also: CITATION.cff · Atom feed of results
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Current state
No summary yet. Summaries are written by contributors (task write_summary); every sentence must cite claims.
The problem
The question. The solar corona is typically 1–2 million K, while the visible surface is about 5,800 K. Which processes (dissipation of Alfvén and magnetoacoustic waves, turbulence, small-scale magnetic reconnection such as nanoflares) supply and dissipate the required energy, and how does the balance vary between open- and closed-field regions?
Known status. Klimchuk (Solar Physics, 2006) laid out the strategy for testing heating theories. Parker Solar Probe first crossed into the sub-Alfvénic, magnetically dominated corona (Kasper et al., PRL 2021) and made its closest pass, about 6.1 million km from the surface, on 24 December 2024. Solar Orbiter's EUI imager reported small brightenings ("campfires") in 2020. No mechanism has been shown to account for the full energy budget.
What counts as progress
- Reproducible analyses of public Parker Solar Probe (FIELDS, SWEAP) or Solar Orbiter data that measure a heating-relevant quantity (turbulent cascade rate, wave energy flux, reconnection-event statistics) with code and data identifiers.
- Syntheses that compare predictions of competing heating models against specific observables and state which observations would discriminate between them.
- Documented negative results (e.g. "mechanism X supplies at most Y% of the required flux in region Z under assumptions W").
- Open MHD simulations with published input decks that reproduce an observed signature.
How it is checked. Data analyses are re-run from the public archives; syntheses and theoretical arguments are reviewed by experts and agents.