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Wave Normal and Poynting Vector Calculations using the Cassini Radio and Plasma Wave InstrumentWave normal and Poynting vector measurements from the Cassini radio and plasma wave instrument (RPWS) are used to examine the propagation characteristics of various plasma waves during the Earth flyby on August 18, 1999. Using the five-channel waveform receiver (WFR), the wave normal vector is determined using the Means method for a lightning-induced whistler, equatorial chorus, and a series of low-frequency emissions observed while Cassini was in the magnetosheath. The Poynting vector for these emissions is also calculated from the five components measured by the WFR. The propagation characteristics of the lightning-induced whistler were found to be consistent with the whistler wave mode of propagation, with propagation antiparallel to the magnetic field (southward) at Cassini. The sferic associated with this whistler was observed by both Cassini and the Stanford VLF group at the Palmer Station in Antarctica. Analysis of the arrival direction of the sferic at the Palmer Station suggests that the lightning stroke is in the same sector as Cassini. Chorus was observed very close (within a few degrees) to the magnetic equator during the flyby. The chorus was found to propagate primarily away from the magnetic equator and was observed to change direction as Cassini crossed the magnetic equator. This suggests that the source region of the chorus is very near the magnetic equator. The low-frequency emission in the magnetosheath has many of the characteristics of lion roars. The average value of the angle between the wave normal vector and the local magnetic field was found to be 16 degrees, and the emissions ranged in frequency from 0. 19 to 0.75 f(sub ce), where f(sub ce) is the electron cyclotron frequency. The wave normal vectors of these waves were primarily in one direction for each individual burst (either parallel or antiparallel to the local field) but varied in direction throughout the magnetosheath. This suggests that the sources of the emissions are far from the spacecraft and that there are multiple source regions.
Document ID
20020043182
Acquisition Source
Jet Propulsion Laboratory
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Hospodarsky, G. B.
(Iowa Univ. Iowa City, IA United States)
Averkamp, T. F.
(Iowa Univ. Iowa City, IA United States)
Kurth, W. S.
(Iowa Univ. Iowa City, IA United States)
Gurnett, D. A.
(Iowa Univ. Iowa City, IA United States)
Dougherty, M.
(Imperial Coll. London United Kingdom)
Inan, Umran
(Stanford Univ. Stanford, CA United States)
Wood, Troy
(Stanford Univ. Stanford, CA United States)
Date Acquired
August 20, 2013
Publication Date
December 1, 2001
Publication Information
Publication: Journal of Geophysical Research
Publisher: American Geophysical Union
Volume: 106
Issue: A12
ISSN: 0148-0227
Subject Category
Astrophysics
Report/Patent Number
Paper-2001JA900114
Funding Number(s)
CONTRACT_GRANT: JPL-961152
Distribution Limits
Public
Copyright
Other

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