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Low‐level VLF and LF radio emissions observed at Earth and Jupiter
Author(s) -
Barbosa D. D.
Publication year - 1982
Publication title -
reviews of geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 8.087
H-Index - 156
eISSN - 1944-9208
pISSN - 8755-1209
DOI - 10.1029/rg020i002p00316
Subject(s) - physics , magnetosphere , computational physics , scattering , noise (video) , radio wave , lower hybrid oscillation , van allen radiation belt , plasma , geophysics , astrophysics , optics , nuclear physics , computer science , cyclotron , quantum mechanics , artificial intelligence , image (mathematics)
This paper examines the current state of knowledge of VLF and LF radio wave emissions in the magnetosphere. Specifically, the properties of the low‐level noise commonly referred to as continuum radiation are reviewed with emphasis on the capabilities of the noise to diagnose local and remote plasma parameters. The relationship of the radiation to ≥1‐mV/m electrostatic upper hybrid emissions is critically assessed. There is a fair amount of indirect observational evidence to suggest that upper hybrid noise is associated with the generation of the VLF‐LF radiation, and proposed theoretical mechanisms lean toward this interpretation also. However, no definitive association has been established to date. The theoretical luminosities of several mechanisms, which include synchrotron radiation, linear mode conversion of upper hybrid waves, and nonlinear scattering of upper hybrid waves off plasma density irregularities, are estimated. The wave‐wave scattering hypothesis is adjudged to be a viable mechanism if the presence of low‐frequency waves as a scattering agent can be established either theoretically or observationally. The alternate mechanisms are considered to be too weak as potential sources, but efficiency‐saving modifications may make the linear mode conversion hypothesis more competitive. Recommendations for future studies on this subject are given.