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Radiation Near 2f(sub p) and Intensified Emissions Near f(sub p) in the Dayside and Nightside Auroral Region and Polar CapThis paper reports the discovery in the DE 1 data of propagating radiation near 2f(sub p) (the H component) and relatively intense electromagnetic waves near f(sub p) with fields typically less than or approximately equal to 1 mV/m (the PF or plasma frequency component) on both the dayside and the nightside of Earth. These emissions are observed at auroral and polar cap latitudes for radial distances ranging from 2.5 to 4.5 R(sub E). The H component is unique in that no other 2f(sub p) emissions are known to be generated where the electron gyrofrequency f(sub g) exceeds 2f(sub p). Since existing theories for 2f(sub p) radiation assume f(sub g)/f(sub p) less than 1, new theories will be required to explain the H component. The PF waves near f(sub p) are electromagnetic, but with large ratios E/cB approximately 20. On the basis of cold plasma theory, the wave frequencies and the ratios E/cB, the PF component plausibly consists of zeta-mode and/or whistler mode waves near f(sub p), presumably driven by an electron instability. The H emissions have modest bandwidths of approximately 50% at frequencies ranging from 5 to 20 kHz. Grounds for interpreting the H component as emissions generated near 2f(sub p) are provided by the very good frequency tracking of the PF and H components and typical frequency ratios near 2.0. Strong evidence exists that part of the H component is propagating, electromagnetic radiation, based on propagation effects and spin modulation patterns. However, no magnetic signals have yet been detected for the H component, so that it could be partly electrostatic. Cold plasma theory and the observed wave characteristics favor interpreting the H component as composed of omicron mode and/or zeta mode signals. Combining the DE 1 observations with rocket observations, it is predicted that the much more intense Langmuir-like fields observed in the low altitude auroral zones should also generate observable 2f(sub p) radiation. This prediction should be testable using Polar and future rocket flights. Directions for future research are also described.
Document ID
19990009289
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Cairns, Iver H.
(Iowa Univ. Iowa City, IA United States)
Menietti, J. D.
(Iowa Univ. Iowa City, IA United States)
Date Acquired
August 19, 2013
Publication Date
March 1, 1997
Publication Information
Publication: Journal of Geophysical Research
Publisher: American Geophysical Union
Volume: 102
Issue: A3
ISSN: 0148-0227
Subject Category
Geophysics
Report/Patent Number
Paper 96JA03559
Funding Number(s)
CONTRACT_GRANT: NAGw-5051
CONTRACT_GRANT: NAGw-2040
CONTRACT_GRANT: NAGw-3461
Distribution Limits
Public
Copyright
Other

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