Abstract
The daily variation of the horizontal intensity of the earth's magnetic field at Honolulu exhibits seasonal features that are not related in a simple way to solar declination. These are illustrated here in monthly curves of the daily variation for quiet days averaged over a considerable number of years. It is believed that these features may arise from the seasonal variation of the large-scale air circulation in the lower ionosphere. It is suggested that a study of the daily magnetic records against large-scale features of daily meteorological maps of the upper stratosphere might find related changes occurring at the two levels and might make possible the use in this way of abundant geomagnetic data in meteorological research.
