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Origins of horizontal divergence in the auroral thermosphere: A modelling study
Author(s) -
Cooper S. L.,
Conde M.
Publication year - 2006
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 - 10.1029/2006gl027601
Subject(s) - divergence (linguistics) , thermosphere , momentum (technical analysis) , geophysics , pressure gradient , convection , temperature gradient , geology , flow (mathematics) , atmospheric sciences , mechanics , inertial frame of reference , physics , classical mechanics , meteorology , ionosphere , philosophy , linguistics , finance , economics
It has widely been presumed that most horizontal divergence in Earth's thermospheric wind field results from pressure gradients established by localized heating. A simplified local‐scale, three‐dimensional, time‐dependent, finite element model has been used to determine other possible sources of horizontal divergence over spatial scales of less than 200 km. In a limited study to test the hypothesis that inertial processes contribute to the generation of horizontal divergence, a non‐divergent, time‐varying ion convection pattern was used to deposit momentum. Divergent neutral winds resulted. Divergence was induced by both localized heating and time varying momentum deposition. Further, for the geometries considered, thermal expansion resulting from heating was the dominant driver of the horizontal gradient perpendicular to the background flow, whereas inertial processes dominated the horizontal gradient parallel to the background flow.