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| Titel |
Selected solar wind parameters at 1 AU through two solar activity cycles |
| VerfasserIn |
R. Bruno, U. Villante, A. Stecca |
| 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 ; 12, no. 2/3 ; Nr. 12, no. 2/3, S.105-112 |
| Datensatznummer |
250010312
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| Publikation (Nr.) |
 copernicus.org/angeo-12-105-1994.pdf |
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| Zusammenfassung |
| In situ measurements of the solar wind
largely cover more than two solar magnetic activity cycles, namely 20 and 21.
This is a very appealing opportunity to study the influence of the activity
cycle on the behaviour of the solar wind parameters. As a matter of fact, many
authors so far have studied this topic comparing the long-term magnetic field
and plasma averages. However, when the average values are evaluated on a data
sample whose duration is comparable with (or even longer than) the solar
rotation period we lose information about the contribution due to the fast and
the slow solar wind components. Thus, discriminating in velocity plays a key
role in understanding solar cycle effects on the solar wind. Based on these
considerations, we performed a separate analysis for fast and slow wind,
respectively. In particular, we found that: (a) fast wind carries a slightly
larger momentum flux density at 1 AU, probably due to dynamic stream-stream
interaction; (b) proton number density in slow wind is more cycle dependent than
in fast wind and decreases remarkably across solar maximum; (c) fast wind
generally carries a magnetic field intensity stronger than that carried by the
slow wind; (d) we found no evidence for a positive correlation between velocity
and field intensity as predicted by some theories of solar wind acceleration;
(e) our results would support an approximately constant divergence of field
lines associated with corotating high-velocity streams. |
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