  The origin of various celestial phenomena have remained mysterious for
conventional astrophysics. Therefore, alternative solutions should be
considered, taking into account the involvement of unstable dark-matter
particle candidates, such as the celebrated axions or other as yet unforeseen
axion-like particles. Their spontaneous and induced decay by the ubiquitous
solar magnetic fields can be at the origin of persisting enigmatic X-ray
emission, giving rise to a steady and a transient/local solar activity,
respectively. The (coherent) conversion of photons into axion(-like) particles
in intrinsic magnetic fields may modify the solar axion spectrum. The reversed
process can be behind transient (solar) luminosity deficits in the visible.
Then, the Sun might be also a strong source of ~eV-axions. Thus, enigmatic
observations might be the as yet missing direct signature for axion(-like)
particles in earth-bound detectors.
