Extended Data Table 1 Characteristics of the magnetometers active during Science Run 2. The station name, location in longitude and latitude, orientation of the sensitive axis, type of magnetometer (NMOR^50,51, rf-driven²⁶, or SERF⁵²), and probed transition are listed. The bandwidth indicates the measured -3 dB point of the magnetometers’ frequency response to oscillating magnetic fields. The calibration error takes into account potential temporal variation of the magnetometers’ calibration over the course of Science Run 2, and is estimated based on auxiliary measurements. The rightmost column lists the estimated ratio between the effective proton spin polarization and the Landé g-factor for the magnetometer, \({\sigma_{\rm{p}}/{g}}\), which depends on the atomic species and the magnetometry scheme as described in Sec. II of the Supplementary Information. The \({\sigma_{\rm{p}}/{g}}\) value is used to relate the measured magnetic field to the signal expected from the interaction of an ALP field with proton spins. The indicated uncertainty describes the range of values from different theoretical calculations²⁹

From: Search for topological defect dark matter with a global network of optical magnetometers