Pseudoscalar conversion and X-rays from the sun

We investigate the detection of a pseudoscalar φ that couples electromagnetically via an interaction 14gφFF̃. In particular, we focus on the conversion of pseudoscalars produced in the sunʹs interior in the presence of the sunʹs external magnetic dipole field and sunspot-related magnetic fields. We find that the sunspot approach is superior. Measurements by the SXT on the Yohkoh satellite can measure the coupling constant down to g = 0.5-1 × 10−10 GeV−1, provided the pseudoscalar mass m < 7×10−6 eV, which makes it competitive with other astrophysical approaches.