Orientation of Birkeland current sheets in the dayside polar region and its relationship to the IMF

Journal Article · Thu May 01 04:00:00 EDT 1980 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA085iA05p01987· OSTI ID:5234879

Saflekos, N A; Potemra, T A

Vector magnetic field observations made with the three-axes magnetometer on the Triad satellite have been used to study the orientation of magnetic disturbances in the dayside polar region. These measurements were all made over the southern polar region and recorded at McMurdo, Antarctica. Thesa distwrbafces are transverse to the main geomagnetic field and may be interpreted as being caused by field-aligned Birkeland current sheets consistent with Maxwell's equatioNs. The current sheets in the regions usuallq associated with the morning and afternoon auroral regions are most often aligned in the geomagnetic east-west direction. The amplitudes of these 'south auroral' currents are larger in the morning than in the afternoon when the interplanetary magnetic field (IMF) is directed toward the sun (B/sub y/<0, B/sub x/>0) and larger in the afternoon when the IMF is directed away (B/sub y/>0, B/sub x/<0). This is the systematically reversed relationship between Birkeland current intensities and IMF found in the northern auroral zone by McDiarmid et at. (1977). The Birkeland current sheets in the region associated with the southern cusp are also aligned in the geomagnetic east-west direction during periods of negative B/sub z/. During the periods of B/sub y/<0 and B/sub x/>0 the Birkeland current flow in the region of the southern cusp is predominantly away from the ionosphere in contrast to the downward flow into the northern cusp as determined earlier (e.g., McDiarmid et al., 1978b; Iijima et al., 1978). The cusp Birkeland current flow directions appear to reverse for B/sub y/>0 and B/sub x/<0. From a search of the Triad data set, some rare examples of magnetic disturbances with a large north-south (noon-midnight) component have been discovered in the polar cap near noon.

• Research Organization: Applied Physics Laboratory, The John Hopkins University, Laurel, Maryland 20810
• OSTI ID: 5234879
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 85:A5; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640203* -- Atmospheric Physics-- Magnetospheric Phenomena-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANTARCTIC REGIONS
AURORAE
CURRENT DENSITY
DAILY VARIATIONS
EARTH ATMOSPHERE
INTERPLANETARY MAGNETIC FIELDS
IONOSPHERE
MAGNETIC FIELDS
MAGNETOSPHERE
PLANETARY IONOSPHERES
PLASMA SHEET
POLAR REGIONS
POLAR-CAP AURORAE
VARIATIONS