On the long term change in the geomagnetic activity during the 20th century
| Autor: | F. Ouattara, C. Amory-Mazaudier, M. Menvielle, P. Simon, J.-P. Legrand |
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| Jazyk: | angličtina |
| Rok vydání: | 2009 |
| Předmět: | |
| Zdroj: | Annales Geophysicae, Vol 27, Pp 2045-2051 (2009) |
| Druh dokumentu: | article |
| ISSN: | 0992-7689 1432-0576 |
| DOI: | 10.5194/angeo-27-2045-2009 |
| Popis: | The analysis of the aa index series presented in this paper clearly shows that during the last century (1900 to 2000) the number of quiet days (Aa The quiet days and very quiet days correspond to periods during which the Earth encounters slow solar wind streams flowing in the heliosheet during the period where the solar magnetic field has a dipolar geometry. Therefore, the observed change in the number of quiet days is the signature of a long term evolution of the solar coronal field topology. It may be interpreted in terms of an increase in the magnitude of the solar dipole, the associated decrease of the heliosheet thickness accounting for the observed decrease in the number of quiet days. |
| Databáze: | Directory of Open Access Journals |
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