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| Titel |
First results from the Cluster wideband plasma wave investigation |
| VerfasserIn |
D. A. Gurnett, R. L. Huff, J. S. Pickett, A. M. Persoon, R. L. Mutel, I. W. Christopher, C. A. Kletzing, U. S. Inan, W. L. Martin, J.-L. Bougeret, H. St. C. Alleyne, K. H. Yearby |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 19, no. 10/12 ; Nr. 19, no. 10/12, S.1259-1272 |
| Datensatznummer |
250014115
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| Publikation (Nr.) |
 copernicus.org/angeo-19-1259-2001.pdf |
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| Zusammenfassung |
In this report we present
the first results from the Cluster wideband plasma wave investigation. The four
Cluster spacecraft were successfully placed in closely spaced, high-inclination
eccentric orbits around the Earth during two separate launches in July –
August 2000. Each spacecraft includes a wideband plasma wave instrument
designed to provide high-resolution electric and magnetic field wave-forms via
both stored data and direct downlinks to the NASA Deep Space Network. Results
are presented for three commonly occurring magnetospheric plasma wave
phenomena: (1) whistlers, (2) chorus, and (3) auroral kilometric radiation.
Lightning-generated whistlers are frequently observed when the spacecraft is
inside the plasmasphere. Usually the same whistler can be detected by all
spacecraft, indicating that the whistler wave packet extends over a spatial
dimension at least as large as the separation distances transverse to the
magnetic field, which during these observations were a few hundred km. This is
what would be expected for nonducted whistler propagation. No case has been
found in which a strong whistler was detected at one spacecraft, with no signal
at the other spacecraft, which would indicate ducted propagation. Whistler-mode
chorus emissions are also observed in the inner region of the magnetosphere. In
contrast to lightning-generated whistlers, the individual chorus elements
seldom show a one-to-one correspondence between the spacecraft, indicating that
a typical chorus wave packet has dimensions transverse to the magnetic field of
only a few hundred km or less. In one case where a good one-to-one
correspondence existed, significant frequency variations were observed between
the spacecraft, indicating that the frequency of the wave packet may be
evolving as the wave propagates. Auroral kilometric radiation, which is an
intense radio emission generated along the auroral field lines, is frequently
observed over the polar regions. The frequency-time structure of this radiation
usually shows a very good one-to-one correspondence between the various
spacecraft. By using the microsecond timing available at the NASA Deep Space
Net-work, very-long-baseline radio astronomy techniques have been used to
determine the source of the auroral kilometric radiation. One event analyzed
using this technique shows a very good correspondence between the inferred
source location, which is assumed to be at the electron cyclotron frequency,
and a bright spot in the aurora along the magnetic field line through the
source.
Key words. Ionosphere
(wave-particle interactions; wave propagation) – Magnetospheric physics
(plasma waves and instabilities; instruments and techniques) |
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