Premium
Vorticity and divergence in the high‐latitude upper thermosphere
Author(s) -
Thayer J. P.,
Killeen T. L.
Publication year - 1991
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 - 10.1029/91gl00131
Subject(s) - thermosphere , vorticity , earth's magnetic field , potential vorticity , atmospheric sciences , physics , latitude , divergence (linguistics) , quiet , polar vortex , atmospheric circulation , geology , ionosphere , climatology , vortex , geophysics , geodesy , meteorology , troposphere , astronomy , magnetic field , linguistics , philosophy , quantum mechanics
Measurements made from the Dynamics Explorer‐2 satellite in November 1981 through January 1982 and November 1982 through January 1983 have been analyzed to determine the divergence and vertical component of vorticity of the high‐latitude neutral wind field in the upper thermosphere for quiet ( Kp ≤3) and active (3+ ≤ Kp ≤6) geomagnetic conditions and for both northern (winter) and southern (summer) hemispheres. This analysis provides the first experimental determination of the large‐scale vorticity and divergence patterns in the polar thermosphere and provides insight into the relative strengths of the different sources of momentum and energy responsible for driving the winds. The principal findings from this work include the following: The mean neutral wind pattern is dominated by rotational flow rather than by divergent flow, with a typical vorticity: divergence ratio of ∼2:1 for active conditions and ∼4:1 for quiet conditions. Comparison of the divergence and vorticity patterns for quiet and active conditions indicates that the divergent component of the neutral flow intensifies more significantly with increasing geomagnetic activity than does the rotational component.