Relationship between sprite streamer behavior and lightning-driven electric fields

摘要

The lightning-driven electric fields not only initiate sprite streamers at high altitudes but also control their propagation to lower altitudes until termination. Thus, the relationship between sprite streamer behavior and their causative lightning-driven ambient electric field can reveal the internal microphysics during sprite development. In this work, we combined the measurements of broadband electromagnetic radiation from sprite-producing lightning, high-speed video of sprite optical emissions acquired at 5,000-10,000 frames per second, and numerical simulations to infer the background lightning-driven electric fields during the full extent of downward streamer propagation. For four sprites analyzed, all with positive polarity downward streamers, the observed streamers all terminate at locations where the ambient electric field is approximately 0.05 EA, independent of the altitude where this field is reached. For two sprites with significant horizontal extent, the points of streamer termination closely follow the spatial contour of the E = 0.05 Ek surface, further confirming the consistency of this termination background field for positive sprite streamers. The positive streamers also begin their significant deceleration where the background field drops below 0.12-0.24 Ek. These measured termination field (Eter) and deceleration field (Edec) are consistent with previous laboratory experiments of positive streamer stopping field and critical field to sustain stable propagation. These results connect sprite streamer behavior with the lightning-driven background electric fields and can be a step to further constrain the existing model of streamer propagation in the mesosphere.