Re-estimatation of the Upper Limit on the Photon Mass with the Solar Wind Method

The currently accepted value for the upper limit on the photon rest mass comes from a rough estimate based on the solar wind method. We reconsider this method and present a more detailed analysis of the electromagnetic fields in interplanetary space. The simple analytic expressions for the solar wind magnetic field, electric field and current are obtained with a finite photon mass. The upper limit on the photon mass is re-estimated as m_γ<0.8×10^?54 kg, which improves the current bound by up a factor of 2, and further confirms the reliability of the solar wind method.