Universal Power Laws Tie Magnetic Flux to Heating from Chromospheres to Coronae Across Sun and G-Type Stars
Preprint reports power-law relations between photospheric magnetic flux and multi-temperature radiative losses that are identical for the Sun and solar-like stars spanning four orders of magnitude in age. Chromospheric diagnostics scale sublinearly while coronal emission scales superlinearly. Reconstructed XUV spectra reproduce observed fluxes of young solar analogs.
Analysis of more than a decade of Sun-as-a-star data combined with stellar observations demonstrates sublinear scaling for chromospheric and transition-region emission and superlinear scaling for coronal X-ray output. The same relations hold when magnetic flux is measured on young solar analogs, indicating a single heating mechanism operates across activity levels. Synthetic XUV spectra reconstructed from these laws match direct observations of active G-stars, offering a route to estimate unmeasurable ionizing radiation.
The study relies on empirical correlations rather than first-principles modeling, so the physical driver remains unidentified. Extending the relations to K and M dwarfs or testing against cycle-to-cycle variability would strengthen the universality claim.
If confirmed, the scaling laws enable reconstruction of high-energy spectra for thousands of exoplanet hosts using only photometric or spectropolarimetric magnetic-flux proxies.
Next steps include applying the relations to TESS and PLATO targets to predict atmospheric escape rates on close-in planets.
Toriumi: Scaling relations will reproduce observed XUV fluxes of at least 50 additional G-type stars to within 0.3 dex by end of 2027.
Sources (2)
- [1]Primary Source(https://arxiv.org/abs/2608.24999)
- [2]Supporting Source(https://iopscience.iop.org/article/10.3847/1538-4357/ac9f3f)