Distinguishing Alfven waves from quasi-static field structures associated with the discrete aurora: Sounding rocket and HILAT satellite measurements

Journal Article · Fri Jun 01 00:00:00 EDT 1990 · Geophysical Research Letters (American Geophysical Union); (USA)

DOI:https://doi.org/10.1029/GL017i007p00921· OSTI ID:6485582

Knudsen, D J; Kelley, M C; Earle, G D ^[1]; Vickrey, J F ^[2]; Boehm, M ^[3]

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1. Cornell Univ., Ithaca, NY (USA)
2. SRI International, Menlo Park, CA (USA)
3. Univ. of California, Berkeley (USA)

The authors present and analyze sounding rocket and HILAT satellite measurements of the low frequency (< 1 Hz) electric and magnetic fields {delta}E and {delta}B perpendicular to the Earth's magnetic field B{sub 0} in the auroral oval. By examining the time-domain field data it is often difficult to distinguish temporal fluctuations from static structures which are Doppler shifted to a non-zero frequency in the spacecraft frame. However, they show that such a distinction can be made by constructing the impedance function Z(f). Using Z(f) they find agreement with the static field interpretation below about 0.1 Hz in the spacecraft frame, i.e. Z(f) = {Sigma}{sub p}{sup {minus}1} where {Sigma}{sub p} is the height-integrated Pedersen conductivity of the ionosphere. About 0.1 Hz the authors find Z(f) > {Sigma}{sub p}{sup {minus}1}, which they argue to be due to the presence of Alfven waves incident from the magnetosphere and reflecting from the lower ionosphere, forming a standing wave pattern. These waves may represent an electromagnetic coupling mechanism between the auroral acceleration region and the ionosphere.

• OSTI ID: 6485582
• Journal Information: Geophysical Research Letters (American Geophysical Union); (USA), Vol. 17:7; ISSN 0094-8276
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAL OVAL
ELECTRIC FIELDS
MAGNETIC FIELDS
FLUCTUATIONS
ALFVEN WAVES
AURORAE
ELECTRIC CONDUCTIVITY
GEOMAGNETIC FIELD
IONOSPHERE
ROCKETS
SATELLITES
STANDING WAVES
EARTH ATMOSPHERE
ELECTRICAL PROPERTIES
HYDROMAGNETIC WAVES
PHYSICAL PROPERTIES
PLANETARY IONOSPHERES
VARIATIONS
640201* - Atmospheric Physics- Auroral
Ionospheric
&amp; Magetospheric Phenomena