Journal cover Journal topic
Annales Geophysicae An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 1.490 IF 1.490
  • IF 5-year value: 1.445 IF 5-year
    1.445
  • CiteScore value: 2.9 CiteScore
    2.9
  • SNIP value: 0.789 SNIP 0.789
  • IPP value: 1.48 IPP 1.48
  • SJR value: 0.74 SJR 0.74
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 88 Scimago H
    index 88
  • h5-index value: 21 h5-index 21
Volume 29, issue 8
Ann. Geophys., 29, 1341–1348, 2011
https://doi.org/10.5194/angeo-29-1341-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 29, 1341–1348, 2011
https://doi.org/10.5194/angeo-29-1341-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.

  05 Aug 2011

05 Aug 2011

The correlation between solar and geomagnetic activity – Part 2: Long-term trends

Z. L. Du Z. L. Du
  • Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China

Abstract. Using lag-correlation function analysis, the correlation coefficient at zero lag (r0), the maximum (rm) and the corresponding lag time (Lm) between solar (Rz) and geomagnetic (aa) activity for a 528-month (44-year) running time window are shown to vary in a declining, declining and rising secular trend, respectively, before 1958. However, these trends changed since 1958 with a rising secular trend in both r0 and rm and without a significant trend in Lm, probably related to a periodicity longer than 140 years. An odd-numbered solar cycle tends to show a higher correlation and a shorter lag time between Rz and aa than the previous even-numbered one, suggesting a 2-cycle periodicity superimposed on secular trends. An even-numbered Hale cycle tends to show a higher correlation and a shorter lag time between Rz and aa than the previous odd-numbered one, suggesting a 4-cycle periodicity superimposed on secular trends. The variations in the correlations may be related to the non-linearity between Rz and aa, and the decreasing trend in the correlation (r0) is not exclusively caused by the increasing trend in the lag time of aa to Rz. These results represent an observational constraint on solar-dynamo models and can help us gain a better understanding of the long-term evolution of solar activities. In applications, therefore, cautions must be taken when using the correlation for molding the dynamical process of the Sun and for predicting solar activities.

Publications Copernicus
Download
Citation