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| Titel |
Magnetic Decreases (MDs) and mirror modes: two different plasma β changing mechanisms |
| VerfasserIn |
B. T. Tsurutani, G. S. Lakhina, O. P. Verkhoglyadova, E. Echer, F. L. Guarnieri |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 17, no. 5 ; Nr. 17, no. 5 (2010-09-27), S.467-479 |
| Datensatznummer |
250013726
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| Publikation (Nr.) |
 copernicus.org/npg-17-467-2010.pdf |
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| Zusammenfassung |
We discuss two different physical processes that create localized high
β plasma regions. One is nonlinear wave-steepening, generating magnetic
decreases (MDs) by a ponderomotive force. The other is the mirror instability
generating alternating high and low β plasma regions. It is
demonstrated that MDs and mirror modes are observationally quite different
structures. MDs spatially occur in interplanetary space and mirror modes
primarily in planetary magnetosheaths. MDs are characterized by: 1) variable
(exponentially decreasing number with increasing) angular changes, 2)
variable (exponentially decreasing) thicknesses, and 3) no characteristic
inter-event spacings. In sharp contrast, mirror modes are characterized by:
1) little or no angular changes across the structures, 2) a characteristic
scale size, and 3) are quasiperiodic in nature.
Arguments are presented for the recently observed magnetic dips in the
heliosheath being mirror mode structures. The sources of free energy for
instability are discussed. Both structures are important for energetic
particle transport in astrophysical and heliospheric plasmas. |
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