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| Titel |
Dynamical changes of the polar cap potential structure: an information theory approach |
| VerfasserIn |
I. Coco, G. Consolini, E. Amata, M. F. Marcucci, D. Ambrosino |
| 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 ; 18, no. 5 ; Nr. 18, no. 5 (2011-10-17), S.697-707 |
| Datensatznummer |
250013976
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| Publikation (Nr.) |
 copernicus.org/npg-18-697-2011.pdf |
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| Zusammenfassung |
| Some features, such as vortex structures often observed through a wide spread
of spatial scales, suggest that ionospheric convection is turbulent and
complex in nature. Here, applying concepts from information theory and
complex system physics, we firstly evaluate a pseudo Shannon entropy, H,
associated with the polar cap potential obtained from the Super Dual Auroral
Radar Network (SuperDARN) and, then, estimate the degree of disorder and the
degree of complexity of ionospheric convection under different Interplanetary
Magnetic Field (IMF) conditions. The aforementioned quantities are computed
starting from time series of the coefficients of the 4th order spherical
harmonics expansion of the polar cap potential for three periods,
characterised by: (i) steady IMF Bz > 0, (ii) steady IMF Bz < 0 and
(iii) a double rotation from negative to positive and then positive to
negative Bz. A neat dynamical topological transition is observed when the
IMF Bz turns from negative to positive and vice versa, pointing toward the
possible occurrence of an order/disorder phase transition, which is the
counterpart of the large scale convection rearrangement and of the increase
of the global coherence. This result has been confirmed by applying the same
analysis to a larger data base of about twenty days of SuperDARN data,
allowing to investigate the role of IMF By too. |
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