On the long term change in the geomagnetic activity during the 20th century
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<20 nT) drastically diminished from a mean annual value greater than 270 days per year at the end of the nineteenth century to a mean value of...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2009-05-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/27/2045/2009/angeo-27-2045-2009.pdf |