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- Wintoft, P, et al.
(författare)
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Predictions of local ground geomagnetic field fluctuations during the 7-10 November 2004 events studied with solar wind driven models
- 2005
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Ingår i: Annales Geophysicae. - 1432-0576. ; 23:9, s. 3095-3101
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Tidskriftsartikel (refereegranskat)abstract
- The 7-10 November 2004 period contains two events for which the local ground magnetic field was severely disturbed and simultaneously, the solar wind displayed several shocks and negative B-z periods. Using empirical models the 10-min RMS Delta X and Delta Y at Brorfelde (BFE, 11.67 degrees E, 55.63 degrees N), Denmark, are predicted. The models are recurrent neural networks with 10-min solar wind plasma and magnetic field data as inputs. The predictions show a good agreement during 7 November, up until around noon on 8 November, after which the predictions become significantly poorer. The correlations between observed and predicted log RMS Delta X is 0.77 during, 7-8 November but drops to 0.38 during 9-10 November. For RMS Delta Y the correlations for the two periods are 0.71 and 0.41, respectively. Studying the solar wind data for other L1-spacecraft (WIND and SOHO) it seems that the ACE data have a better agreement to the near-Earth solar wind during the first two days as compared to the last two days. Thus, the accuracy of the predictions depends on the location of the spacecraft and the solar wind flow direction. Another finding, for the events studied here, is that the Delta X and Delta Y models showed a very different dependence on B-z The Delta X model is almost independent of the solar wind magnetic field B-z except at times when B-z is exceptionally large or when the overall activity is low. On the contrary, the Delta Y model shows a strong dependence on B-z at all times.
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