AbstractPhase and amplitude measurements of VLF radio waves propagating subionospherically on long paths across the Arctic are used to determine the high latitude, daytime D region height, and sharpness of the bottom edge of the Earth's ionosphere. The principal path used is from the 23.4‐kHz transmitter, DHO, in north Germany, northward across the Arctic passing ~2° from the North Pole, and then southward to Nome, Alaska, thus avoiding most land and all thick ice. Significant observational support is obtained from the also nearly all‐sea path from JXN in Norway (~67°N, 16.4 kHz) across the North Pole to Nome. By suitably comparing measurements with modeling using the U.S. Navy code LWPC, the daytime D region (Wait) height and sharpness parameters in the Arctic are found to be H′ = 73.7 ± 0.7 km and β = 0.32 ± 0.02 km−1 in the summer of 2013, that is, at (weak) solar maximum. It is also found that, unlike at lower latitudes, very low frequency phase and amplitude recordings on (~1,000 km) paths at high subarctic latitudes show very little change with solar zenith angle in both phase and amplitude during daytime for solar zenith angles <~80°. It is concluded that, at high latitudes, the daytime lower D region is dominated by nonsolar ionizing sources in particular by energetic particle precipitation (>~300 keV for electrons) with a contribution from galactic cosmic rays, rather than by solar Lyman α which dominates at low and middle latitudes.