Pseudoscalar Conversion and X-rays from the Sun

We investigate the detection of a pseudoscalar φ that couples electromagnetically via an interaction 1 4 gφF F̃ . In particular, we focus on the conversion of pseudoscalars produced in the sun’s interior in the presence of the sun’s external magnetic dipole field and sunspotrelated 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. ∗Address after August 1: Olin Physical Laboratory, Wake Forest University, Winston-Salem NC 27109