title: Plasma irregularities in the D-region ionosphere in association with sprite streamer initiation.
abstract: Sprites are spectacular optical emissions in the mesosphere induced by transient lightning electric fields above thunderstorms. Although the streamer nature of sprites has been generally accepted, how these filamentary plasmas are initiated remains a subject of active research. Here we present observational and modelling results showing solid evidence of pre-existing plasma irregularities in association with streamer initiation in the D-region ionosphere. The video observations show that before streamer initiation, kilometre-scale spatial structures descend rapidly with the overall diffuse emissions of the sprite halo, but slow down and stop to form the stationary glow in the vicinity of the streamer onset, from where streamers suddenly emerge. The modelling results reproduce the sub-millisecond halo dynamics and demonstrate that the descending halo structures are optical manifestations of the pre-existing plasma irregularities, which might have been produced by thunderstorm or meteor effects on the D-region ionosphere.
authors.affiliation: Communications and Space Sciences Laboratory, Department of Electrical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Jianqi
authors.initials: J
authors.lastname: Qin
authors.affiliation: Communications and Space Sciences Laboratory, Department of Electrical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Victor P
authors.initials: VP
authors.lastname: Pasko
authors.affiliation: Department of Physics, United States Air Force Academy, Colorado Springs, Colorado 80840, USA.
authors.forename: Matthew G
authors.initials: MG
authors.lastname: McHarg
authors.affiliation: Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA.
authors.forename: Hans C
authors.initials: HC
authors.lastname: Stenbaek-Nielsen