Solar or meteorological control of lower ionospheric fluctuations (2-15 and 27 days) in middle latitudes

摘要

Several types of short and long term effects of solar activity on the lower ionosphere are related to solar flares, the sector structure of the interplanetary magnetic field and some periodicities in sunspots or solar radio flux. The most evident periodicities of the Sun are the 11 year cycle of its activity and the differential rotation period near 27 days (25 to 30 days). Here, the following questions are discussed: which periods between 2 and 15 days and near 27 days occur in ionospheric absorption during the interval July 1980 to July 1985 and are these periods related to similar periods in solar Ly-alpha flux, geomagnetic activity, or neutral wind near 95 km observed in Collm (GDR). Day-time absorption data obtained by the A3 method was used for the following radio-paths: (164 kHz), (1539 kHz), (6090 kHz). With the use of these data the electron density variations in the lower ionosphere can be analyzed. An attempt was made to clarify the nature of the observed fluctuations in absorption.