Empirical Parameterizations of ULF Power and Drift Orbit Averaged Radial Diffusion Coefficients From Ground Magnetometers for Different MLT

Abstract

Radial diffusion, driven by ultra‐low frequency (ULF) waves, is an important process for the transport of electrons in the outer radiation belt. Ground magnetometers give us constant observations of such ULF waves but their usefulness is limited by the models used to transform ground measurements into their progenitor fields in space. A typical assumption is that of a dipole field, and so measurements can only be reliably performed during the day. We have chosen a series of 17 magnetometer stations at different sets of geomagnetic latitudes, with stations in each set separated by several hours in longitude, and compared their Pc5 (1.67–6.67 mHz) ULF power measurements, and the resulting calculated radial diffusion coefficients, from 11 years of their data. By comparing the mismatch of their results when they were in different time sectors, and for different values of Kp, we were able to assess the median deviation of measurements conducted before dawn or after dusk with those on the day side. This will be useful for projects requiring a longitudinally limited array of magnetometers, such as FARBES (Forecast of Actionable Radiation Belt Scenarios), or for parts of the world where such coverage is limited.