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Onset conditions for equatorial spread F determined during EQUIS II
Author(s) -
Hysell D. L.,
Larsen M. F.,
Swenson C. M.,
Barjatya A.,
Wheeler T. F.,
Sarango M. F.,
Woodman R. F.,
Chau J. L.
Publication year - 2005
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2005gl024743
Subject(s) - ionosphere , thermosphere , incoherent scatter , sporadic e propagation , plasma , f region , geophysics , geology , radar , wind shear , shear (geology) , rocket (weapon) , atmospheric sciences , physics , geodesy , meteorology , aerospace engineering , wind speed , petrology , quantum mechanics , engineering
An investigation into the dynamics and layer structure of the postsunset ionosphere prior to the onset of equatorial spread F (ESF) took place during the NASA EQUIS II campaign on Kwajalein Atoll on August 7 and 15, 2004. On both nights, an instrumented rocket measured plasma number density and vector electric fields to an apogee of about 450 km. Two chemical release rockets were launched both nights to measure lower thermospheric wind profiles. The Altair UHF/VHF radar was used to monitor coherent and incoherent scatter. In both experiments, strong plasma shear flow was detected. Periodic, patchy bottom‐type scattering layers were observed in the westward‐drifting plasma below the shear nodes. The large‐scale plasma depletions that formed later during ESF reproduced the periodic structure of the original, precursor layers. The layers were therefore predictive of the ESF that followed. We surmise that collisional shear instabilities may have given rise to large‐scale plasma waves that were highlighted by the bottom‐ type layer structure and that preconditioned the postsunset ionosphere for ESF.