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| Titel |
Spatial distribution of spectral parameters of high latitude geomagnetic disturbances in the Pc5/Pi3 frequency range |
| VerfasserIn |
N. V. Yagova, V. A. Pilipenko, L. N. Baransky, M. J. Engebretson |
| 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 ; 28, no. 9 ; Nr. 28, no. 9 (2010-09-28), S.1761-1775 |
| Datensatznummer |
250016888
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| Publikation (Nr.) |
 copernicus.org/angeo-28-1761-2010.pdf |
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| Zusammenfassung |
| We analyze spectral parameters of the geomagnetic disturbances
within the 1–4 mHz (Pc5/Pi3) frequency range for 29
observatories from polar to auroral latitudes. The main object of
this study is the broadband (noise) background under quiet and
moderately disturbed conditions. To obtain a quantitative
description of background high-latitude long period ULF activity
the log-log dependence of the spectral power on frequency is
expanded over Legendre polynomials, and the coefficients of this
expansion (spectral moments) are used to describe the most common
features of these spectra. Not only the spectral power, but also
the spectral slope and higher spectral moments, averaged over
relatively long time intervals, demonstrate a systematic
dependence on corrected geomagnetic (CGM) latitude, Φ, and
magnetic local time, MLT. The 2-D distributions of the spectral
moments in Φ-MLT coordinates are characterized by
existence of structures, narrow in latitude and extended in MLT,
which can be attributed to the projections of different
magnetospheric domains. Spatio-temporal distributions of spectral
power of elliptically (P-component) and randomly (N-component)
polarized signal are similar, but not identical. The N-component
contribution to the total signal becomes non-negligible in regions
with a high local activity, such as the auroral oval and dayside
polar cusp. The spectral slope indicates a larger relative
contribution of higher frequencies upon the latitude decrease,
probably, as a result of the resonant effects in the ULF noise.
The higher spectral moments are also controlled mostly by CGM
latitude and MLT and are fundamentally different for the polarized
and non-polarized components. This study is a step towards the
construction of an empirical model of the ULF wave power in
Earth's magnetosphere. |
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