Flares as fingerprints of inner solar darkness

TL;DR

This paper investigates whether solar X-ray flares could be signatures of axions, proposing a scattering mechanism that explains observed spectra and suggesting potential axion properties, but finds current models insufficient to match observations.

Contribution

It introduces a scattering-based explanation for solar X-ray signals as axion signatures and constrains axion properties based on solar observations.

Findings

Scattering can explain the energy distribution of solar X-ray signals.

Simulations suggest axion rest mass around 0.01 eV.

Current models cannot fully reproduce observed intensities.

Abstract

X-ray flares and other solar brightenings have been discarded as potential axion signatures. An axion X-ray signal must appear exclusively near the disk centre, and its spectrum must peak at ~4.2keV, contrary to observation. We argue here that due to Compton scattering off the (plasma) electrons the outward propagation of X-rays from axions converted near the Sun's surface can explain energy distribution and non direcivity. Simulation points at the photosphere as the birth place of the presumed axion conversion, implying an axion rest mass of ~0.01eV. At present, even optimistic parameter values can not reproduce the measured intensities. The simulated photon spectrum peaks at low energies. Quiet Sun hard X-rays are in favour of massive and/or light axion involvement.