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| Titel |
Plasma and wave phenomena induced by neutral gas releases in the solar wind |
| VerfasserIn |
H. Laakso  , R. Grard, P. Janhunen , J.-G. Trotignon |
| 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 ; 20, no. 1 ; Nr. 20, no. 1, S.1-11 |
| Datensatznummer |
250014338
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| Publikation (Nr.) |
 copernicus.org/angeo-20-1-2002.pdf |
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| Zusammenfassung |
We investigate plasma and
wave disturbances generated by nitrogen (N2) gas releases from the cooling
system of an IR-camera on board the Vega 1 and Vega 2 spacecraft, during their
flybys of comet Halley in March 1986. N2 molecules are ionized by solar UV
radiation at a rate of ~ 7 · 10-7 s-1 and give rise to a
plasma cloud expanding around the spacecraft. Strong disturbances due to the
interaction of the solar wind with the N+2 ion cloud are
observed with a plasma and wave experiment (APV-V instrument). Three gas
releases are accompanied by increases in cold electron density and simultaneous
decreases of the spacecraft potential; this study shows that the spacecraft
potential can be monitored with a reference sensor mounted on a short boom. The
comparison between the model and observations suggests that the gas expands as
an exhaust plume, and approximately only 1% of the ions can escape the beam
within the first meters. The releases are also associated with significant
increases in wave electric field emission (8 Hz–300 kHz); this phenomenon
lasts for more than one hour after the end of the release, which is most likely
due to the temporary contamination of the spacecraft surface by nitrogen gas.
DC electric fields associated with the events are complex but interesting. No
magnetic field perturbations are detected, suggesting that no significant
diamagnetic effect (i.e. magnetic cavity) is associated with these events.
Key words. Ionosphere (planetary
ionosphere) – Space plasma physics (active perturbation experiments;
instruments and techniques) |
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