Oscillations of the Sun and the geomagnetic field

Abstract

THE suggestion by Toth¹ that the reported long-period oscillations of the solar atmosphere^2,3 may be observed as oscillations of the geomagnetic field is an intriguing idea. It was suggested¹ that the ∼2 h 40 min oscillations found in geomagnetic field data recorded at Tihany, Hungary, could reflect, through one of two possible mechanisms, similar period solar oscillations. In the first the geomagnetic field might have natural oscillations at this frequency that could produce environmental changes in the atmosphere^4,5 and/or ionosphere and/or magnetosphere that would cause the ground-based telescope observations to reach erroneous conclusions. In the second mechanism the oscillations in the solar atmosphere might produce similar frequency oscillations in the interplanetary magnetic field which, through coupling with the geomagnetic field at 1 AU, would cause similar period variations in the field at the Earth's surface. Such oscillations would be in the range of periods of solar wind fluctuations measured near Earth and often attributed to Alfvén waves⁶. Regular, periodic variations in the interplanetary magnetic field with a period near that of the reported solar oscillations have not been reported. We have spectral analysed geomagnetic field data on the same days as those published by Toth¹ using data from our fluxgate magnetometer stations in New Hampshire and in Quebec and data from the conjugate area at Siple Station, Antarctica⁷.