Numerical simulation of an elve modulated by a gravity wave

Abstract

AbstractRecent video observations have shown that elves—the visible manifestation of the lightning electromagnetic pulse (EMP) interacting with the lower ionosphere—can be modulated by neutral density fluctuations at lower ionosphere altitudes due to gravity waves. The elve emissions thus illuminate the gravity wave structure. Here we use a finite difference time domain (FDTD) model of the lightning EMP to simulate elve emissions in the presence of neutral density fluctuations representative of gravity waves. We show that observable elve striations can be generated by gravity waves with a neutral density perturbation of as low as 5% at elve altitudes near 85 km. Higher perturbations lead to more pronounced striations. The depth of the optical signature perturbation is found to be similar in magnitude to the neutral density perturbation at elve altitudes, although the relationship depends on viewing geometry, gravity wave geometry, and the elve‐causative lightning peak current moment.