Persistence of Quasi-2-Day Oscillations in the Geomagnetic Activity Indices
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It is found that quasi-2-day oscillations persist in the geomagnetic activity indices a<SUB><I>n</I></SUB>, a<SUB><I>s</I></SUB> and a<SUB><I>m</I></SUB> and time variations of the oscillation characteristics are examined. The 3-hourly indices for 1964-1986 are used for analysis. The main results are: 1) the oscillation persists almost continuously, 2) there are not significant hemispheric differences of the oscillation period and amplitude, 3) the dominant period is 48 hours, 4) there is expressed a semi-annual variation of the oscillation period with minimum in solstices and maximum in equinoxes, 5) the oscillation amplitude is modulated by semi-annual and long-term geomagnetic variations. A possible way for inducing such oscillations in the time variations of geomagnetic activity indices is proposed.
- Earth, Planets and Space
Earth, Planets and Space 48(10), 1233-1239, 1996-10
Society of Geomagnetism and Earth, Planetary and Space Sciences