Analysis of Electric and Magnetic Lightning-Generated Wave Amplitudes Measured by the Van Allen Probes

We provide a statistical analysis of both electric and magnetic field wave amplitudes of very low frequency lightning-generated waves (LGWs) based on the equivalent of 11.5 years of observations made by the Van Allen Probes encompassing similar to 24.6 x 10(6) survey mode measurements. We complement this analysis with data from the ground-based World Wide Lightning Location Network to explore differences between satellite and ground-based measurements. LGW mean amplitudes are found to be low compared with other whistler mode waves (1 1.6 pT and 19 59 mu V/m). Extreme events (1/5,000) can reach 100 pT and contributes strongly to the mean power below L = 2. We find excellent correlations between World Wide Lightning Location Network-based power and wave amplitudes in space at various longitudes. We reveal strong dayside ionospheric damping of the LGW electric field. LGW amplitudes drop for L < 2, contrary to the Earth's intense equatorial lightning activity. We conclude that it is difficult for equatorial LGW to propagate and remain at L < 2. Plain Language Summary Lightning flashes emit powerful electromagnetic lightning-generated waves (LGWs). Some of this power propagates and escapes into the magnetosphere. Resonant interactions of trapped electrons in the Van Allen belts with LGWs cause pitch angle diffusion, leading to scattering of those electrons into the atmosphere, an important process for estimating the radiation levels encountered by satellites in low Earth orbits. Here, we analyze the electric and magnetic field wave amplitudes of LGWs measured by the two National Aeronautics and Space Administration Van Allen Probes during their entire mission. We compare these spacecraft observations with an estimate for the very low frequency (VLF) wave power escaping to space using the ground-based World Wide Lightning Location Network to measure lightning VLF radiation on Earth. We discuss the main features of the LGW amplitude distributions with respect to position relative to the Sun (local time), magnetic field lines (L-shell, L), longitude, and time (month or season). Monthly and yearly statistics of electric and magnetic LGW amplitudes are generated and reveal an important decay below L = 2 indicating that LGW VLF power is not efficiently transmitted into space on Earth's lowest latitude magnetic field lines, particularly during the day.