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| Titel |
Magnetic clouds in the Earth's magnetosheath: a statistical study |
| VerfasserIn |
Lucile Turc, Dominique Fontaine, Emilia Kilpua, Philippe Escoubet |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250126412
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| Publikation (Nr.) |
 EGU/EGU2016-6130.pdf |
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| Zusammenfassung |
| Magnetic clouds (MCs) are highly geoeffective solar wind transients. In the interplanetary
space, they possess a well-defined magnetic structure, characterised by an enhanced and
smoothly rotating magnetic field. We examine here whether their magnetic structure is
modified when they encounter the outer regions of the geospace, namely the bow shock and
the magnetosheath. Significant changes in the magnetic structure of MCs could in turn affect
the level of geomagnetic activity they induce in the near-Earth’s space. In this work, we study
82 MCs during which spacecraft observations are available simultaneously in the solar wind
and in the magnetosheath. The observations inside the magnetosheath are related to the bow
shock properties using a magnetosheath model (Turc et al., 2014, Ann. Geophys.). We find
that the variation of an MC’s magnetic field orientation from the solar wind to the
magnetosheath is directly related to the encountered shock configuration. The angle between
the magnetic field in the magnetosheath and that in the solar wind shows a very good
correlation with the ΘBn angle (between the upstream magnetic field and the normal
to the shock’s surface) encountered at the bow shock’s crossing. Because of its
importance for the geoeffectivity, we examine how the magnetic field North-South
(Bz) component is modified across the bow shock. In some cases, we find that Bz
reverses in the magnetosheath. The conditions during which such reversals occur are
investigated and their implications in terms of the MCs’ geoeffectivity are discussed. |
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