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| Titel |
Modelling long-term trends in lunar exposure to the Earth's plasmasheet |
| VerfasserIn |
M. Hapgood |
| 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 ; 25, no. 9 ; Nr. 25, no. 9 (2007-10-02), S.2037-2044 |
| Datensatznummer |
250015918
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| Publikation (Nr.) |
 copernicus.org/angeo-25-2037-2007.pdf |
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| Zusammenfassung |
| This paper shows how the exposure of the Moon to the Earth's plasmasheet is
subject to decadal variations due to lunar precession. The latter is a key
property of the Moon's apparent orbit around the Earth – the nodes of that
orbit precess around the ecliptic, completing one revolution every 18.6
years. This precession is responsible for a number of astronomical
phenomena, e.g. the year to year drift of solar and lunar eclipse periods.
It also controls the ecliptic latitude at which the Moon crosses the
magnetotail and thus the number and duration of lunar encounters with the
plasmasheet. This paper presents a detailed model of those encounters and
applies it to the period 1960 to 2030. This shows that the total lunar
exposure to the plasmasheet will vary from 10 h per month at a minimum
of the eighteen-year cycle rising to 40 h per month at the maximum.
These variations could have a profound impact on the accumulation of charge
due plasmasheet electrons impacting the lunar surface. Thus we should expect
the level of lunar surface charging to vary over the eighteen-year cycle.
The literature contains reports that support this: several observations made
during the cycle maximum of 1994–2000 are attributed to bombardment and
charging of the lunar surface by plasmasheet electrons. Thus we conclude
that lunar surface charging will vary markedly over an eighteen-year cycle
driven by lunar precession. It is important to interpret lunar environment
measurements in the context of this cycle and to allow for the cycle when
designing equipment for deployment on the lunar surface. This is
particularly important in respect of developing plans for robotic
exploration on the lunar surface during the next cycle maximum of 2012–2019. |
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