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Ground-based Pc5 ultralow frequency (ULF) wave power in multiple ground-based meridians is compared to the very low frequency (VLF) wave amplitude proxy, derived from Polar Operational Environmental Satellite (POES) precipitation, for the 33 storms studied by Li et al. (2015, ). The results reveal common L-shell and time profiles for the ULF waves and VLF proxy for every single storm, especially at L6, and identical discrimination between efficient and inefficient radiation belt electron acceleration. The observations imply either ULF waves play a role in driving precipitation, which is falsely interpreted as VLF wave power in the proxy, ULF waves drive VLF waves (the reverse being energetically unfeasible), or both have a common driver with nearly identical L-shell and time dependence. Global ground-based ULF wave power coherence implies that a small number of meridians can be used to estimate storm time radial diffusion coefficients. However, the strong correspondence between ULF wave power and VLF wave proxy complicates causative assessments of electron acceleration.

Plain Language Summary Several studies have been using satellites to indirectly infer the presence of a type of very low frequency (VLF) waves by measuring the precipitation of electrons down to Earth. By using ground instruments to measure the power of ultralow frequency (ULF) waves during a set of geomagnetic storms, we find that their morphology almost perfectly matches that of the inferred VLF ones. This suggests either that the ULF waves cause precipitation themselves, thereby polluting the indirect method of inferring VLF waves, or that they produce VLF waves, or that both ULF and VLF waves are produced at the same time and place by a common cause. Since the presence of ULF or VLF waves is needed for different methods of electron acceleration in space, this observation affects the discussion on which method is more important during geomagnetic storms. We also find that those ULF wave measurements are very similar for different terrestrial longitudes.