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A new geomagnetic limit on the photon mass m_γ is derived from an analysis of satellite measurements of the Earth's magnetic field H{→}. The primary effect of a nonzero photon mass is to generate an additional contribution to H{→} resembling that from an external source. We find m_γ{≤}8×{}10^-16 eV/c²=1×{}10^-48 g=4×{}10^-9 m^-1. The same data are also used to set new limits on long-range fields coexisting with electromagnetism.
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Fischbach et al. (1994) studied this question.
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