Iridium Communications Satellite Constellation Data for Study of Earth's Magnetic Field

Characterization of Earth's magnetic field is key to understanding dynamics the core. We assess whether Iridium Communications magnetometer data can be used for this purpose since. The 66 satellites are in 86° inclination, 780 km altitude, circular orbits, with 11 each six orbit planes. In one day constellation returns 300,000 measurements spanning globe <2° spacing. from January 2010 through November 2015, and compared against International Geomagnetic Reference Field (IGRF-11) inter-calibrate all same model. Geomagnetically quiet 24-h intervals were selected using total Birkeland current, auroral electrojet, ring current indices. z-scores these quantities combined quietest 16 quarter analysis. Residuals between IGRF-11 yield consistent patterns that evolve gradually 2015. binned 9° latitude by longitude distributions about mean bin Gaussian 1-sigma standard errors ?3 nT. Spherical harmonic coefficients computed time series identify artifacts at precession (8 months) seasonal (12 periods their harmonics which then removed notch filtering. This analysis yields 800 virtual geomagnetic observatories providing a global map single data. results CHAOS 7.4 generally agree, but systematic differences larger than statistical uncertainties present warrant further exploration.