Does the Magnetosphere Behave Differently on Weekends?

A. Karinen1, K. Mursula1, Th.Ulich2, and J. Manninen2

1Dept of Physical Sciences, University of Oulu, Oulu, Finland
2Sodankylä Geophysical Observatory, Sodankylä, Finland


Global geomagnetic activity has been suggested to be enhanced during weekends above the weekly average after 1940s. Before 1940s weekends and weekdays were found to be equally active. This so-called "weekend effect" was suggested to be due to VLF range harmonics of the radiation emitted by electric power lines (power line harmonic radiation, PLHR). 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 reanalyze the suggested "weekend effect" in global geomagnetic activity using the 69-year planetary geomagnetic Ap index and the 133-year antipodal aa index. We conclude that there is no statistically significant "weekend effect" during the interval covered by these geomagnetic activity indices. Although global geomagnetic activity is slightly enhanced on weekends from 1940s to 1980s, the more recent data show rather a decrease of global geomagnetic activity on weekends, contrary to the expected increase of the "weekend effect" due to increasing power consumption.

Proceedings of the Euroconference Solar Cycle and Space Weather 2001 (SOLSPA), 439-442, ESA-SP-477, 2002.