The influence of long-period dynamo region winds on the surface geomagnetic field elements

Abstract

Periodic analyses of H and Z are presented, and it is verified that the annual and quasi‐biennial waves in H and Z can be caused by dynamo effects. Such waves need not appear in the spectra of geomagnetic activity indexes, such as Ap. An estimate of the annual wave in H produced by the annual wave in ionospheric wind speed yields a reasonable amplitude. It is suggested that the quasi‐biennial oscillation in H and Z is also caused by ionospheric winds.

Latitudinal variation of quasi‐biennial oscillation modulation of the semidiurnal tide in the lower thermosphere

“…Several authors have analyzed continuous ground-based magnetometer records for the presence of a QBO signature in the geomagnetic field absolute components. Kalinin [1954, [London and Matsushita, 1963;Shapiro and Ward, 1964;Curtie, 1966] or, confiictingly, have reported finding [Stacey and Westcott, 1962;Curvie, 1973;Nastrom and Belmont, 1976] the existence of a periodicity in geomagnetic data between 25 and 29 months. In particular, Nastrom and Belmont [1976] found QBO signatures (mean period -029 months) in geomagnetic records over the complete range of latitudes from 89øN through the equator to 71øS over one solar cycle (1960)(1961)(1962)(1963)(1964)(1965)(1966)(1967)(1968)(1969)(1970)(1971)(1972)).…”