Correlation between magnetic and electric field perturbations in the field-aligned current regions deduced from DE 2 observations

Journal Article · Tue Sep 01 04:00:00 EDT 1992 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/92JA00110· OSTI ID:6893031

Ishii, M; Iyemori, T ^[1]; Sugiura, M ^[2]; Slavin, J A ^[3]

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1. Kyoto Univ. (Japan)
2. Tokai Univ., Tokyo (Japan)
3. NASA Goddard Space Flight Center, Greenbelt, MD (United States)

Satellite observational have shown high correlation between magnetic and electric field perturbations in the high-latitude field-aligned current regions. The high correlation has been interpreted by two models. In the first, the Static model, the observed perturbations are regarded as being static spatial variations, and the ratio of the orthogonal magnetic and electric field components [Delta]B[sub z]/E[sub x] represents the height-integrated ionospheric Pedersen conductivity [Sigma][sup P]. In the second, Alfven wave model, the observed perturbations are interpreted as being Doppler-shifted Alfven waves, and the inverse of the ratio gives the Alfven wave velocity V[sub A]. In this paper the authors investigate changes of this ratio with spatial scale length, using the DE 2 observations. The ratio [Delta]B[sub z]/E[sub x] is found to change little with scale length for variations of scale lengths longer than 64 km, or 8.0 s in time. While for variations of smaller scale lengths, which are obtained using numerical filters with cutoff periods shorter than 4.0 s, the same ratio shows a significant dependence on scale length. The calculated ratios are nearly equal to [Sigma][sub P] based on an ionospheric model for long-wavelength structures and to 1/V[sub A] for short-wavelength variations. The transition from the former to the latter usually begins around 4.0-8.0 s on the time scale. On the dayside the correlation between [Delta]B[sub z] and E[sub x] is generally high, and the transition is clearly seen. Thus the static model is applicable to variations of scale lengths greater than 8.0 s (or 64 km); while the Alfven wave effect becomes increasingly dominant for scale lengths less than 4.0 s (or 32 km). For scale lengths below about 5 km ([approximately]0.6 s) the short-circuiting effect at ionospheric altitudes higher than the altitudes at which the horizontal Pedersen closure current usually flows becomes appreciable.

• OSTI ID: 6893031
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 97:A9; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

661320* -- Auroral
Ionospheric
& Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALFVEN WAVES
CORRELATIONS
CURRENTS
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTRIC CONDUCTIVITY
ELECTRIC CURRENTS
ELECTRIC FIELDS
ELECTRICAL PROPERTIES
ELECTRODYNAMICS
HYDROMAGNETIC WAVES
IONOSPHERE
MAGNETIC FIELDS
MATHEMATICAL MODELS
PHYSICAL PROPERTIES
PLANETARY IONOSPHERES
SATELLITES