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Ann. Geophys., 20, 1137-1142, 2002
www.ann-geophys.net/20/1137/2002/
© European Geosciences Union 2002
Does the magnetosphere behave differently on weekends?
A. Karinen1, K. Mursula1, Th. Ulich2, and J. Manninen2
1Department of Physical Sciences, P.O. Box 3000, University of Oulu, FIN-90014 Oulu, Finland
2Sodankylä Geophysical Observatory, Tähteläntie 62, FIN-99600 Sodankylä, Finland
Correspondence to: A. Karinen (arto.karinen@oulu.fi)
Abstract. Global geomagnetic
activity has been suggested to be enhanced during weekends above the weekly
average after 1930. Before the 1930s, weekends and weekdays were found to be
equally active. This so-called "weekend effect" was suggested to be
due to power line harmonic radiation (PLHR) in the VLF range emitted by
electric power lines. Since the consumption of electric power is different on
weekends and weekdays, leading to different PLHR intensities, this could
possibly cause the "weekend effect" in global geomagnetic activity.
In the present paper, we reanalyse the suggested "week-end effect" in
global geomagnetic activity using the 69-year planetary geomagnetic Ap
index and the 131-year antipodal aa index. We conclude that there is no
statistically significant "weekend effect" during the interval
covered by these geo-magnetic activity indices. Although global geomagnetic
activity is slightly enhanced on weekends from the 1930s to the 1980s, the more
recent data show rather a relative decrease in global geomagnetic activity on
weekends, contrary to the expected increase in the "weekend effect",
due to increasing power consumption. Moreover, the weekly distribution is
fairly similar in solar wind speed and global geomagnetic activity during the
last 35 years, further supporting the view that the "weekend effect"
is only a statistical fluctuation.
Key words. Geomagnetism and
paleomagnetism (time variations, diurnal to secular) – Magnetospheric physics
(planetary magnetospheres; storms and substorms)
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