Using the eight daily K numbers (three-hour-range indices) for six observatories in moderately low latitudes and fairly well distributed in longitude, a universal-time component of the daily variation of irregular geomagnetic fluctuations having an apparently significant amplitude in the yearly average has been found in the data for the nine years 1940–1948. It is suggested that a portion of magnetic disturbance may be produced by dynamo action in the ionosphere, and give rise to this yearly-average universal-time component.