Accession Number : ADA140586

Title :   Low Frequency Electric and Magnetic Noise along the Auroral Field Lines.

Descriptive Note : Progress rept.,


Personal Author(s) : Gurnett,D A ; Huff,R L ; Menietti,J D ; Winningham,J D ; Burch,J L

PDF Url : ADA140586

Report Date : Feb 1984

Pagination or Media Count : 56

Abstract : Plasma wave and plasma measurements from the DE-1 spacecraft are used to investigate an intense band of low frequency, 100 Hz, electric and magnetic noise detected at low altitudes over the auroral zones. This noise is observed by DE-1 on essentially every low altitude pass over the auroral zone and occurs in regions of intense low energy, 100 eV to 10 keV, electron precipitation and field-aligned currents. The electric field polarization in a plane perpendicular to the static magnetic field is random. Correlation measurements between the electric and magnetic fields show that the perpendicular (approx. north-south) electric field fluctuations are closely correlated with the perpendicular (east-west) magnetic field fluctuations, and that the Poynting flux is directed downward, toward the Earth. The total electromagnetic power flow associated with these fluctuations is very large, approx. 10 to the 8th power watts. Two interpretations of the low frequency noise are considered: first, that the noise is produced by quasi-static fields imbedded in the ionosphere, and second, that the noise is due to Alfven waves propagating along the auroral field lines. For the quasi-static interpretation, the ratio of the magnetic to electric field strengths is determined by the Pedersen conductivity at the base of the ionosphere, whereas for the Alfven wave interpretation it is determined by the Alfven index of refraction.

Descriptors :   *Ionosphere, *Noise(Electrical and electromagnetic), *Aurorae, *Magnetohydrodynamic waves, Plasma waves, Intensity, Low altitude, Low energy, Extremely low frequency, Superlow frequency, Polar regions, Alignment, Electric fields, Magnetic fields, Variations, Polarization, Electrons, Wave propagation, Correlation, Electrical conductivity, Refractive index

Subject Categories : Atmospheric Physics
      Plasma Physics and Magnetohydrodynamics
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE