In this paper, we study the solar-terrestrial rela-
tion through the wavelet analysis. We report periodicities
common between multiple solar wind coupling functions
and geomagnetic indices during five solar cycles and also
and the strength of this correspondence. The Dst (found
to be most predictable in Newell et al., J. Geophys. Res.
Space Phys. 112(A1):A01206, 2007) and AL (least pre-
dictable in Newell et al., J. Geophys. Res. Space Phys.
112(A1):A01206, 2007) indices are used for this purpose.
During the years 1966–2016 (which includes five solar cy-
cles 20, 21, 22, 23, and 24), prominent periodicities ≤ 720
days with power above 95% confidence level were found to
occur around 27, 182, 385, and 648 days in the Dst index
while those in the AL index were found in bands around 27,
187, and 472 days. Ten solar wind coupling functions were
then used to find periodicities common with the indices. All
the coupling functions had significant power in bands cen-
tered around 27, 280, and 648 days while powers in fluctu-
ations around 182, 385, and 472 days were only found in
some coupling functions. All the drivers and their variants
had power above the significant level in the 280–288 days
band, which was absent in the Dst and AL indices. The nor-
malized scale averaged spectral power around the common
periods in the coupling functions and the indices indicated
that the coupling functions most correlated with the Dst in-
dex were the Newell (27 and 385 days), Wygant (182 days),
and Scurry-Russell and Boynton (648 days) functions. An
absence of common power between the coupling functions
B T. Andriyas
tushar.andriyas@aggiemail.usu.edu
1 Centre of Material Sciences, Institute of Inter Disciplinary
Studies, University of Allahabad, Allahabad, India
2 Water Engineering and Management, School of Engineering and
Technology, Asian Institute of Technology, Khlong Luang,
Pathumthani 12120, Thailand
and the Dst index around the annual periodicity was noted
during the even solar cycles. A similar analysis for the AL
index indicated that Newell (27 days), Rectified (187 days),
and Boynton (472 days) were the most correlated functions.
It was also found that the correlation numbers were rela-
tively weaker for the AL index, specially for the 187 day
periodicity. It is concluded that as the two indices respond
to solar wind forcing with varying levels of strength at var-
ious prominent scales and the coupling function used, the
response might be dependent on the scale (days or months
or years) of interest at which the solar wind driving is to be
predicted.

EB00000004206K

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• Periodicities in solar wind-magnetosphere coupling functions and geomagnetic activity during the past solar cycles