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| Titel |
Magnetic turbulence spectrum at electron scales in the solar wind |
| VerfasserIn |
Olga Alexandrova, Catherine Lacombe, André Mangeney |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250052833
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| Zusammenfassung |
| Dissipation of the magnetic turbulence in the collisionless plasma of the solar wind is still an
open question. Kolmogorov scaling observed at MHD scales in the solar wind comes to end
at ion scales, where a spectral break is observed. This indicates that a partial dissipation on
ions happens. However, above this break another power-law is observed indicating that a new
cascade takes place. It was supposed that this small scale cascade ends at electron scales.
Recently, observations at electron scales become possible with STAFF instrument on Cluster
mission. In the works of Alexandrova et al. [2009, 2010], it was shown that the turbulent
spectrum at electron scales is curved and not a power-law. This curvature of the
spectrum at electron scales indicates the onset of dissipation. In the present study we
verify the universality of this finding. We analyze 170 spectra calculated over 10
minutes time intervals in the free solar wind, not connected to the Earth’s bow-shock.
Among these spectra, only ~ 20 of them show signatures of parallel propagated
whistler waves. Other 150 spectra have a curved shape and no signatures of particular
wave modes. These curved spectra seem to represent a usual state of turbulence at
electron scales. The superposition of these spectra gives one quasi-universal curved
spectrum, that is the most important result of the present study. We show as well
that the spectral level at electron scales varies mainly with the solar wind thermal
pressure. Correlations with magnetic and dynamic pressures are also observed. |
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