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| Titel |
The influence of solar wind variability on magnetospheric ULF wave power |
| VerfasserIn |
D. Pokhotelov, I. J. Rae, K. R. Murphy, I. R. Mann |
| 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 ; 33, no. 6 ; Nr. 33, no. 6 (2015-06-08), S.697-701 |
| Datensatznummer |
250121207
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| Publikation (Nr.) |
 copernicus.org/angeo-33-697-2015.pdf |
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| Zusammenfassung |
| Magnetospheric ultra-low frequency (ULF) oscillations in the Pc 4–5 frequency
range play an important role in the dynamics of Earth's radiation belts, both
by enhancing the radial diffusion through incoherent interactions and through
the coherent drift-resonant interactions with trapped radiation belt
electrons. The statistical distributions of magnetospheric ULF wave power are
known to be strongly dependent on solar wind parameters such as solar wind
speed and interplanetary magnetic field (IMF) orientation. Statistical characterisation of ULF wave power in
the magnetosphere traditionally relies on average solar wind–IMF conditions
over a specific time period. In this brief report, we perform an alternative
characterisation of the solar wind influence on magnetospheric ULF wave
activity through the characterisation of the solar wind driver by its
variability using the standard deviation of solar wind parameters rather than
a simple time average. We present a statistical study of nearly one solar
cycle (1996–2004) of geosynchronous observations of magnetic ULF wave power
and find that there is significant variation in ULF wave powers as a function
of the dynamic properties of the solar wind. In particular, we find that the
variability in IMF vector, rather than variabilities in other parameters
(solar wind density, bulk velocity and ion temperature), plays the strongest
role in controlling geosynchronous ULF power. We conclude that, although
time-averaged bulk properties of the solar wind are a key factor in driving
ULF powers in the magnetosphere, the solar wind variability can be an
important contributor as well. This highlights the potential importance of
including solar wind variability especially in studies of ULF wave dynamics
in order to assess the efficiency of solar wind–magnetosphere
coupling. |
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