Solar Chameleons
  We analyse the creation of chameleons deep inside the sun and their
subsequent conversion to photons near the magnetised surface of the sun. We
find that the spectrum of the regenerated photons lies in the soft X-ray
region, hence addressing the solar corona problem. Moreover, these
back-converted photons originating from chameleons have an intrinsic difference
with regenerated photons from axions: their relative polarisations are mutually
orthogonal before Compton interacting with the surrounding plasma. Depending on
the photon-chameleon coupling and working in the strong coupling regime of the
chameleons to matter, we find that the induced photon flux, when regenerated
resonantly with the surrounding plasma, coincides with the solar flux within
the soft X-ray energy range. Moreover, using the soft X-ray solar flux as a
prior, we find that with a strong enough photon-chameleon coupling the
chameleons emitted by the sun could lead to a regenerated photon flux in the
CAST pipes, which could be within the reach of CAST with upgraded detector
performance. Then, axion helioscopes have thus the potential to detect and
identify particles candidates for the ubiquitous dark energy in the universe.
