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| Titel |
Twisted magnetic flux tubes in the solar wind |
| VerfasserIn |
Teimuraz Zaqarashvili, Zoltan Voros, Ivan Zhelyazkov, Yasuhito Narita, Roberto Bruno |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088689
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| Publikation (Nr.) |
 EGU/EGU2014-2826.pdf |
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| Zusammenfassung |
| Magnetic flux tubes in the solar wind can be twisted as they are transported from the solar
surface, where the tubes are twisted owing to photospheric motions. The twisted magnetic
tubes can be detected as the variation of total (thermal+magnetic) pressure during
their passage through observing satellite. The twist of isolated magnetic tube may
explain the observed abrupt changes of magnetic field direction at tube walls. For
the tubes aligned with the Parker spiral, the twist angle can be estimated from the
change of magnetic field direction. The twisted tubes are unstable to kink instability
when the twist exceeds a critical value. It is shown that the critical twist angle of
the tube with a homogeneous twist is 70 degree, but the angle can be decreased
owing to the motion of the tube with regards to the solar wind stream. Tangential
velocity discontinuity near the boundaries of individual tubes may also result in the
Kelvin-Helmholtz instability. It is shown that the axial magnetic field stabilizes the
instability in the case of sub-Alfvenic speeds. But even small twist in the external
magnetic field allows the Kelvin-Helmholtz instability to be developed for any
speed. Therefore, twisted magnetic flux tubes can be unstable to Kelvin-Helmholtz
instability when they move with small speed relative to main solar wind stream.
The Kelvin-Helmholtz vortices may significantly contribute into the solar wind
turbulence.
The research leading to these results has received funding from the European
Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement N
313038/STORM and from the Austrian “Fonds zur Förderung der wissenschaftlichen
Forschung” under project P24740-N27. |
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