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| Titel |
WIND observations of coherent electrostatic waves in the solar wind |
| VerfasserIn |
A. Mangeney, C. Salem, C. Lacombe, J.-L. Bougeret, C. Perche, R. Manning, P. J. Kellogg, K. Goetz, S. J. Monson, J.-M. Bosqued |
| 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 ; 17, no. 3 ; Nr. 17, no. 3, S.307-320 |
| Datensatznummer |
250013687
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| Publikation (Nr.) |
 copernicus.org/angeo-17-307-1999.pdf |
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| Zusammenfassung |
The time domain sampler (TDS) experiment on
WIND measures electric and magnetic wave forms with a sampling rate which
reaches 120 000 points per second. We analyse here observations made in the
solar wind near the Lagrange point L1. In the range of frequencies above
the proton plasma frequency fpi and smaller than or of the
order of the electron plasma frequency fpe, TDS observed three
kinds of electrostatic (e.s.) waves: coherent wave packets of Langmuir waves
with frequencies f ~ fpe, coherent wave packets
with frequencies in the ion acoustic range fpi <
f < fpe, and more or less isolated non-sinusoidal
spikes lasting less than 1 ms. We confirm that the observed frequency of the low
frequency (LF) ion acoustic wave packets is dominated by the Doppler effect: the
wavelengths are short, 10 to 50 electron Debye lengths λD.
The electric field in the isolated electrostatic structures (IES) and in the LF
wave packets is more or less aligned with the solar wind magnetic field. Across
the IES, which have a spatial width of the order of ~ 25λD,
there is a small but finite electric potential drop, implying an average
electric field generally directed away from the Sun. The IES wave forms, which
have not been previously reported in the solar wind, are similar, although with
a smaller amplitude, to the weak double layers observed in the auroral regions,
and to the electrostatic solitary waves observed in other regions in the
magnetosphere. We have also studied the solar wind conditions which favour the
occurrence of the three kinds of waves: all these e.s. waves are observed more
or less continuously in the whole solar wind (except in the densest regions
where a parasite prevents the TDS observations). The type (wave packet or IES)
of the observed LF waves is mainly determined by the proton temperature and by
the direction of the magnetic field, which themselves depend on the latitude of
WIND with respect to the heliospheric current sheet.
Key words. Interplanetary physics (plasma waves and
turbulence; solar wind plasma). Space plasma physics (electrostatic structures). |
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