Satellite observations of a new type of discrete VLF emission at L < 4

Journal Article · Tue Mar 01 04:00:00 EST 1988 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA093iA03p01817· OSTI ID:6096038

Poulsen, W L; Inan, U S ^[1]

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1. Stanford Univ., CA (United States)

A new type of discrete whistler mode emission has been observed in the magnetosphere at L < 4. The emission elements are confined to a bandwidth of 1-5 kHz, with the lower cutoff frequency of the band varying with L shell, being equal to {approximately} 0.2-0.5f{sub Heq}, where f{sub Heq} is the equatorial electron gyrofrequency. The discrete and burstlike nature of the emissions is similar to that of chorus emissions typically observed at higher L; however dispersion of individual elements is often different from typical chorus, and the emissions are observed inside as well as outside the plasmapause. The phenomenon seems to occur mainly in the early morning local time sector (0400-0800 MLT) and is well correlated with geomagnetic activity, occurring mostly when {Sigma}Kp > 30. The analysis of data from the low-altitude ISIS 2 and the high-altitude DE 1 satellites indicates that the emissions may be generated near the equatorial plane at frequencies of {approximately}0.2f{sub Heq} inside and {approximately}0.35f{sub Heq} outside the plasmapause. The parallel energy of electrons for gyroresonance with the observed waves is found to be {approximately}20-50 keV in both cases. Observations in the vicinity of low-altitude crossings of the plasmapause also indicate the presence of a second emission band which is interpreted to result from the reflection of the equatorially generated emissions from the lower ionosphere.

• OSTI ID: 6096038
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 93:A3; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

661320* -- Auroral
Ionospheric
&amp; Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COORDINATES
CORRELATIONS
DATA ANALYSIS
DISTURBANCES
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTROMAGNETIC RADIATION
GEOMAGNETIC COORDINATES
IONOSPHERE
MATHEMATICS
NOISE
PLANETARY IONOSPHERES
PLASMAPAUSE
RADIATIONS
RADIO NOISE
RADIOWAVE RADIATION
SATELLITES
SPECTRA
STATISTICS
WHISTLERS