  According to the model ($\Lambda$CDM), based on deep cosmological
observations, the current universe is constituted of 5$\%$ baryonic matter and
25 $\%$ non-baryonic cold dark matter (of speculative origin). These include
quanta of scalar filed like dilaton($\phi$) of scale symmetry origin and quanta
of pseudoscalar field of extra standard model symmetry ( Peccei-Quinn) origin,
like axion ($\phi'$). These fields couple to di-photons through dim-5
operators. In magnetized medium, they in principle can interact with the three
degrees of freedom (two transverse ($A_{\parallel,\perp}$) and one longitudinal
($A_{L}$)) of photon($\gamma$) as long as the total spin is conserved. Because
of intrinsic spin being zero, both $\phi$ and $\phi'$ could in principle have
interacted with $A_{L}$, (having $s_{z}=0$). However, out of $\phi$ and $\phi'$
only one interacts with $A_{L}$. Furthermore, the ambient external magnetic
field and media, breaks the intrinsic Lorentz symmetry of the system invoking
Charge conjugation, Parity and Time reversal symmetries, we analyse the mixing
dynamics of $\phi\gamma$ and $\phi'\gamma$ systems and the structural {\it
difference} of their mixing pattern. The strength of electromagnetic (EM)
signals due to $\phi\gamma$ and $\phi'\gamma$ mixing as a result would be {\it
different}. We conclude by commenting on the possibility of detecting this {\it
difference} -- in polarimetric observables the EMS -- using the existing
space-borne detectors.
