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| Titel |
Magnetic field and dynamic pressure ULF fluctuations in coronal-mass-ejection-driven sheath regions |
| VerfasserIn |
E. K. J. Kilpua, H. Hietala, H. E. J. Koskinen, D. Fontaine, L. Turc |
| 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 ; 31, no. 9 ; Nr. 31, no. 9 (2013-09-10), S.1559-1567 |
| Datensatznummer |
250086107
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| Publikation (Nr.) |
 copernicus.org/angeo-31-1559-2013.pdf |
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| Zusammenfassung |
| Compressed sheath regions form ahead of interplanetary coronal mass ejections
(ICMEs) that are sufficiently faster than the preceding solar wind. The
turbulent sheath regions are important drivers of magnetospheric activity,
but due to their complex internal structure, relatively little is known on the
distribution of the magnetic field and plasma variations in them. In this
paper we investigate ultra low frequency (ULF) fluctuations in the
interplanetary magnetic field (IMF) and in dynamic pressure (Pdyn) using
a superposed epoch analysis of 41 sheath regions observed during solar cycle
23. We find strongest fluctuation power near the shock and in the vicinity of
the ICME leading edge. The IMF and Pdyn ULF power have different
profiles within the sheath; the former is enhanced in the leading part of the
sheath, while the latter is increased in the trailing part of the sheath. We
also find that the ICME properties affect the level and distribution of the
ULF power in sheath regions. For example, sheath regions associated with
strong or fast ICMEs, or those that are crossed at intermediate distances from
the center, have strongest ULF power and large variation in the power
throughout the sheath region. The weaker or slower ICMEs, or those that are
crossed centrally, have in general considerably weaker ULF power with
relatively smooth profiles. The strong and abrupt decrease of the IMF ULF
power at the ICME leading edge could be used to distinguish the ICME from the
preceding sheath plasma. |
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