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Coherent structure generated in the boundary layer of a laboratory‐created ionospheric depletion
Author(s) -
Liu Yu,
Cao Jinxiang,
Xu Liang,
Zhang Xiao,
Wang Pi,
Wang Jian,
Du Yinchang,
Zheng Zhe
Publication year - 2014
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 - 10.1002/2014gl059211
Subject(s) - ionosphere , electron density , boundary layer , instability , electron , plasma , physics , electron temperature , turbulence , nonlinear system , geophysics , depletion region , f region , langmuir probe , computational physics , mechanics , plasma diagnostics , voltage , quantum mechanics
Laboratory experiments have been conducted to simulate the boundary processes of ionospheric depletion. The ionospheric depletion was modeled through releasing depletion chemical ( S F 6 ) into the ambient plasmas. These plasmas were segregated into two regions by a boundary layer of width electric scale length. In the localized boundary layer, the electron density decreased sharply that yielded steep density gradients. Meanwhile, the floating potential increased in the time scales of the lower hybrid (LH) period, which produced strong sheared electron flows. The shear frequency ω s = V E / L E , which characterizes the sheared flow, is much larger than the LH frequency ω LH . A coherent structure was observed when the floating potential fluctuations were analyzed using digital spectral analysis techniques. Comparison with the theory indicated that the structure is driven by the electron‐ion hybrid instability which is generated owing to the nonlinear coupling between the electron density gradient and the sheared electron flow. Our results are important to study the early phase nonlinear evolution of the ionospheric depletion, especially in the development of plasma irregularities and turbulence in the boundary layer.