A Study of Post-Sunset Spread-F Initiation During the 2013 EVEX Campaign

Erhan Kudeki, Pablo Reyes, Aaron Wallace, Bingqian Ye, Robert F. Pfaff, Miguel F. Larsen, Keith M. Groves

Research output: Contribution to journalArticlepeer-review


Equatorial Vortex Experiment (EVEX), the EVEX mission of May 2013, carried out from Roi-Namur, Kwajalein Atoll, explored the initiation physics of equatorial spread-F with a pair of rockets launched simultaneously during local sunset to apogees of 182 and 331 km, respectively. EVEX measurements presented in this paper establish the existence of a differential zonal flow between plasma and neutrals at bottom-side F-region heights during the sunset time in support of a post-sunset spread-F initiation mechanism described in Kudeki et al. (2007) that is characterized by large growth rates for oblique-propagating 10's-of-km-scale electron density perturbations. F-region plasma drifts were measured in situ using an electric field double-probe instrument while neutral winds were measured by triangulating drifting vapor clouds. The state of the ionosphere and spread-F irregularities were monitored by ground based ARPA Long-Range Tracking and Instrumentation Radar and Illinois Radar Interferometer System radars using incoherent and coherent scatter techniques, respectively, as well as an ionosonde.

Original languageEnglish (US)
Article numbere2021JA030256
JournalJournal of Geophysical Research: Space Physics
Issue number5
StatePublished - May 2022

ASJC Scopus subject areas

  • Space and Planetary Science
  • Geophysics


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