D region electron profiles observed with substantial spatial and temporal change near thunderstorms

Abstract

AbstractBroadband lightning signals are used to probe the D region ionosphere with a temporal resolution of 5 min and a spatial resolution of ~50 × 50 km. Together with a full wave propagation model, this technique allows determination of the reference height, h′, and steepness parameter, β, of an exponential electron density profile sensitive to the range of 106–108 electrons/m3. Daytime and nighttime background electron profiles away from thunderstorms are presented, as well as profiles from three regions nearby and atop thunderstorms. The average daytime profile parameters are found to be h′ = 67.7 km with a standard deviation of 0.9 km and β = 0.7 km−1 with a standard deviation of 0.1 km−1. Average nighttime parameters are h′ = 80.9 km with a standard deviation of 1.3 km and β = 2.8 km−1 with a standard deviation of 0.2 km−1. Nighttime electron profiles nearby and atop thunderstorms show slightly higher values of h′ (82.5–84.2 km) and significantly lower values of β (0.9–1.5 km−1). These findings indicate that there is significant electron depletion above ~80 km near and atop thunderstorms during the nighttime. Detailed analysis also shows substantial profile variations in space and time related to lightning discharges due to localized electron enhancement at high altitudes and reduction at lower altitudes. Nevertheless, the general depletion at higher altitudes appears to be related to the overall electrical behavior of the thunderstorm but not directly to lightning activity.