A feasibility study for measuring geomagnetic conversion of solar axions to x-rays in low Earth orbits

Abstract

We present a detailed computation of the expected rate for geomagnetic conversion of solar axions to x-rays (GECOSAX) along the orbit of an x-ray satellite. We use realistic satellite orbits and propagation in time. A realistic model for the Earth's magnetic field, which properly accounts for its spatial non-uniformity, is used. We also account for the effect of the Earth's atmosphere on the propagation of x-rays in our calculation of axion-photon conversion probability. To estimate possible sensitivities to the axion-photon coupling g_aγ, we use an actual measurement of the expected backgrounds by the SUZAKU satellite. Assuming an effective detector area of 10³ cm² and about 10⁶ s of data, we show that a 2 σ limit of g_aγ<(4.7-6.6) × 10^-11 GeV^-1 from GECOSAX is achievable, for axion masses m_a<10^-4 eV. This significantly exceeds current laboratory sensitivities to g_aγ.