ELF PROPAGATION AND EMISSION IN THE MAGNETOSPHERE
Abstract
Considerable research progress has been achieved on ELF signals in the magnetosphere as a consequence of satellite and ground-based studies. Attention is focused on the frequency band from 0.2 to 500 Hz, which is well below the minimum electron plasma and cyclotron frequencies, so that the hydromagnetic approximation applies. Although the magneto-ionic medium is anisotropic and inhomogeneous, the propagation theory for the fast and Alfven modes in homogeneous media is adequate at these frequencies. The signal velocity of the fast mode is essentially isotropic for frequencies below the lower hybrid resonance. The Alfven mode is restricted to frequencies below the proton cyclotron frequency and its signal velocity is closely guided by the geomagnetic field. The morphology of these modes in remote regions of the magnetosphere is being developed from satellite studies. Statistics are available now on the ELF noise distributions with latitude, local time, and geomagnetic activity. Studies based on ground observations have concentrated on dispersion, polarization, and amplitude analyses.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1969
- Accession Number
- AD0696292
Entities
People
- H. B. Liemohn
Organizations
- Boeing