The influence of IMF B sub y on the high-latitude thermospheric circulation during northward IMF

Journal Article · Tue Jan 01 04:00:00 EST 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/90JA01996· OSTI ID:5190139

McCormac, F G; Killeen, T L; Thayer, J P ^[1]

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1. Univ. of Michigan, Ann Arbor (USA)

Thermospheric neutral wind data, obtained by the Fabry-Perot Interferometer and Wind and Temperature Spectrometer on the Dynamics Explorer 2 satellite during periods of northward interplanetary magnetic field (IMF B{sub z} positive), show a dependence of the circulation on the magnitude and sign of the east-west component (B{sub y}) of the IMF. Averaged thermospheric neutral wind vector fields, for the northern hemisphere, and data from several sets of satellite orbits, that illustrate the variation in the neutral wind structure as a function of time and IMF orientation, are presented and discussed. The results show that near December solstice, at solar maximum: (1) sunward neutral winds develop inside the geomagnetic polar cap during periods of persistent positive B{sub z} and relatively low B{sub y}; (2) typical time delays in the establishment of sunward winds following a northward turning of the IMF are approximately 4 hours; (3) sunward winds are not observed when the magnitude of the B{sub z} component of the IMF is less than +4 nT; (4) the maximum-velocity antisunward winds, in the central geomagnetic polar cap region, are on the duskside (dawnside) in the northern hemisphere during periods of northward IMF and B{sub y} negative (positive). A similar asymmetry exists in the sunward flow in the center of the polar cap; (5) if the absolute magnitude of the B{sub y} component of the IMF exceeds that of B{sub z} (i.e., if the B{sub y}/B{sub z} ratio is greater than 1.0) then sunward winds inside the geomagnetic polar cap are rarely observed; instead, one sees a pattern of neutral winds similar to that expected for the given sign of B{sub y} under southward IMF conditions; (6) the summer hemisphere has neutral wind signatures that are similar to those seen in the winter hemisphere for B{sub z} northward, i.e., sunward winds occur in the polar cap for persistently northward B{sub z}, provided the magnitude of B{sub y} does not exceed that of B{sub z}.

• OSTI ID: 5190139
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 96:A1; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640200* -- Atmospheric Physics
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ASYMMETRY
ATMOSPHERIC CIRCULATION
CURRENTS
EARTH ATMOSPHERE
EARTH PLANET
ELECTRIC CURRENTS
ELECTRIC FIELDS
EXPLORER SATELLITES
INTERPLANETARY MAGNETIC FIELDS
ION DRIFT
MAGNETIC FIELDS
MOMENTUM TRANSFER
NORTHERN HEMISPHERE
PLANETS
POLAR REGIONS
SATELLITES
THERMOSPHERE
TIME DELAY
WIND