The 27-Day Variation of Solar Activity, Cosmic Ray Intensity and Geomagnetic Activity.
Final scientific rept.,
UPPSALA UNIV (SWEDEN) COSMIC RAY GROUP
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Zurich relative sunspot numbers, 10.7 cm solar radio flux, cosmic ray neutron monitor intensities and geomagnetic Ap-data during 1958-69 and geomagnetic Kp-data during 1932-69 have been analysed by use of time series methods to study variations with periods 5-40 days and correlations between the parameters. All the parameters show a 27-day variation. For the cosmic ray intensity and the geomagnetic activity this variation is dependent of the solar cycle. By use of filtering techniques the cosmic ray intensity and the geoagnetic activity are studied on individual solar rotations for 1958-69. From power spectrum analysis on geomagnetic Kp-data 1932-69 higher harmonics of the 27-day period are generally found. For many years there exist a 13.5-day variation with a magnitude excluding it to be an effect of the mathermatical treatment. The effect may tentatively be related to the active longitudes on the sun. Author
- Atmospheric Physics