Overlooked Astrophysical Signatures of Axion(-Like) Particles

Abstract

We discuss solar signatures suggesting axion(-like) particles. The working principle of axion helioscopes can be behind unexpected solar X-ray emission, even above 3.5 keV from non-flaring active regions. Because this is associated with solar magnetic fields (~B 2 ), which become in this framework the catalyst and not the otherwise suspected / unspecified energy source of solar X-rays. In addition, the built-in fine tuning we may (not) be able to fully reconstruct, and, we may (not?) be able to copy. Solar axion signals are transient X-ray brightenings, or, continuous radiation from the corona violating the second law of thermodynamics and Planck"s law of black body radiation. To understand the corona problem and other mysteries like flares, sunspots, etc., we arrive at two exotica: a) trapped, radiatively decaying, massive axions allow a continuous self-irradiation of the Sun, explaining the sudden temperature inversion ~2000 km above the surface and b) outstreaming light axions interact with local fields (~B 2 ), depending crucially on the plasma frequency which must match the axion rest mass, explaining the otherwise unpredictable transient, but also continuous, solar phenomena. Then, the photon energy of a related phenomenon might point at the birth place of involved axions. For example, this suggests that the ~2 MK solar corona has its axion roots at the top of the radiative zone. The predicted B ≈ 10-50 T make this place a coherent axion source, while the multiple photon scattering enhances the photon-to-axion conversion unilaterally, since axions escape. We conclude that the energy range below some 100 eV is a window of opportunity for axion searches, and that it coincides with a) the derived photon energies for an external self-irradiation of the Sun, which has to penetrate until the transition region, and b) with the bulk of the soft solar X-ray luminosity of unknown origin. Thus, (in)direct signatures support axions or the like as an explanation of enigmatic behavior in the Sun and beyond; e.g., the otherwise unexplained "solar oxygen crisis" taking into account related observations (~B 2 ) in pores, which is associated with X-ray emission. Axion antennas could take advantage of such a feed back. Finally, the observed soft X-ray emission from the quiet Sun at highest latitudes as well as the extended activity associated with magnetic structures crossing the solar disk centre suggest that a multicomponent axion(-like) scenario is at work.

Towards a new generation axion helioscope

“…The current CAST results have been used already to constrain further WISPs such as weakly coupled hidden photons [21,22]. The proposed NGAH could be extremely valuable to test further these scenarios and survey the existence of other exotica such as chameleons [23], minicharged particles [24,25] or more involved ALP models which have been recently invoked to understand some puzzling features of solar dynamics [26][27][28]. The motivations for various new particles at the low-energy frontier of elementary particle physics, their embedding and role in extensions of the standard model, and our current knowledge about them have been reviewed recently [29].…”

Searching for Decaying Axionlike Dark Matter from Clusters of Galaxies

“…1 and discussion in Ref. [9]). The shape of the spectrum of the predicted KK-axion spectrum is tightly FIG.…”

New mechanism producing axions in the AQN model and how the CAST can discover them

“…Therefore, in the present work, we choose not to specify the instruments which are most suitable and capable for such an analysis. Generically speaking, the proper instruments must be either wide-band by default, or, they must implement the fast scanning mode [49,50,52].…”

“…[49,51,52]. Interestingly, in recent work [53], an amplification factor by as much as 1.2 × 10 11 is given for the Sun as gravitational lens for incident light downstream at about 520 AU.…”