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| Titel |
On the relationship between interplanetary coronal mass ejections and magnetic clouds |
| VerfasserIn |
E. K. J. Kilpua, A. Isavnin, A. Vourlidas, H. E. J. Koskinen, L. Rodriguez |
| 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. 7 ; Nr. 31, no. 7 (2013-07-23), S.1251-1265 |
| Datensatznummer |
250019069
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| Publikation (Nr.) |
 copernicus.org/angeo-31-1251-2013.pdf |
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| Zusammenfassung |
| The relationship of magnetic clouds (MCs) to interplanetary coronal mass
ejections (ICMEs) is still an open issue in space research. The view that all
ICMEs would originate as magnetic flux ropes has received increasing
attention, although near the orbit of the Earth only about one-third of ICMEs
show clear MC signatures and often the MC occupies only a portion of the more
extended region showing ICME signatures. In this work we analyze 79 events
between 1996 and 2009 reported in existing ICME/MC catalogs (Wind magnetic cloud
list and the Richardson and Cane ICME list) using near-Earth observations by
ACE (Advanced Composition Explorer) and Wind. We perform a systematic comparison of cases where ICME and MC
signatures coincided and where ICME signatures extended significantly beyond
the MC boundaries. We find clear differences in the characteristics of these
two event types. In particular, the events where ICME signatures continued
more than 6 h past the MC rear boundary had 2.7 times larger speed
difference between the ICME's leading edge and the preceding solar wind, 1.4
times higher magnetic fields, 2.1 times larger widths and they experienced
three times more often strong expansion than the events for which the rear
boundaries coincided. The events with significant mismatch in MC and ICME
boundary times were also embedded in a faster solar wind and the majority of
them were observed close to the solar maximum. Our analysis shows that the
sheath, the MC and the regions of ICME-related plasma in front and behind the
MC have different magnetic field, plasma and charge state characteristics,
thus suggesting that these regions separate already close to the Sun. Our
study shows that the geometrical effect (the encounter through the CME leg
and/or far from the flux rope center) does not contribute much to the
observed mismatch in the MC and ICME boundary times. |
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