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Mursula et al. 1991
Mursula, K., Kangas, J., Pikkarainen, T. and Kivinen, M. (1991). Pc 1 micropulsations at a high-latitude station: A study over nearly four solar cycles. Journal of Geophysical Research 96: doi: 10.1029/91JA01374. issn: 0148-0227.

An old but rarely used resonance method is introduced and examined in order to study the very long term occurrence of Pc 1 micropulsations. By this method it is possible to detect Pc 1 pulsations with a frequency close to the eigenfrequency of the magnetometer system. We have analyzed the magnetograms of the LaCour-type magnetometer used in a quick-run operation at the high-latitude station of Sodankyl¿, Finland. The eigenfrequencies of the three components covered the frequency range from about 0.3 to 0.5 Hz. Our analysis extends over the whole registration period from 1932 to 1944 and from 1953 to 1983, i.e., covering nearly four solar cycles. The results show a very strong negative correlation between the annual Pc 1 activity and the annual sunspot number which persists over the whole data period. According to the statistics obtained, it is, for example, very unlikely that Pc 1 activity maximum at a high-latitude station would occur during the declining phase of the sunspot cycle. Furthermore, as a result of the negative correlation, some of the differences between the various solar cycles can be seen in the corresponding cycles of annual Pc 1 activity. Our results also reveal some new features common for the long-term variations of Pc 1 activity. Our results also reveal some new features common for the long-term variations of Pc 1 activity at high- and mid-latitude stations and help in understanding the differences between them. ¿ American Geophysical Union 1991

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Abstract

Keywords
Magnetospheric Physics, MHD waves and instabilities, Magnetospheric Physics, Magnetospheric configuration and dynamics, Magnetospheric Physics, Instruments and techniques
Journal
Journal of Geophysical Research
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Publisher
American Geophysical Union
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