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| Titel |
Tail Ballooning Modes in Global Simulations at Substorm Onset |
| VerfasserIn |
J. Raeder, P. Zhu, Y. S. Ge |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063630
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| Zusammenfassung |
| It is generally accepted that magnetic reconnection is the main
mechanism that dissipates power during a substorm. It is less
clear, however, whether the beginning of magnetic reconnection
in the magnetotail also signifies the onset of the substorm
expansion phase itself, i.e., whether the "outside-in" scenario
applies, or if a different process happens first closer to Earth
that triggers the reconnection onset in the magnetotail, i.e.,
the "inside-out" scenario. Global MHD simulations have generally
supported the "outside-in" scenario. However, ideal MHD
instabilities that could possibly trigger tail reconnection may
have been missed due to coarse numerical resolution or due to
other numerical effects. Here, we present results from
OpenGGCM substorm simulations that clearly
show growth of the ballooning mode (large ky) as suggested by our earlier
analysis (Zhu et al., 2009), as well as growth of an ideal-like
instability that is purely axial, i.e., with zero ky.
The signatures af the ballooning mode in the model is in good agreement
with observations, i.e., ~0.5 RE wavelength and associated auroral
bead structures, whereas the axial mode appears to be related
to entropy anti-diffusion and bubble-blob formation. |
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