Effect of ionospheric e-region dynamo current on the daily variation of geomagnetic field

The daily variation of the Earth's magnetic field has been one of the subjects that have interested the scientists for a long time. With the discovery of the ionosphere, the source of this variation was thought to be the dynamo current in the E-region of the ionosphere. Many scientists have theoretically shown that the variation in the magnetic field of the earth is caused by the dynamo current. The daily change of the geomagnetic field in the quite days of solar activity is one of the important issues studied. In this study, the relationship between the electric current in the E-region and the daily change of the geomagnetic field has been investigated numerically. The current densities generated by the E-region dynamo current and the mathematical expressions of the magnetic field created by these currents on the earth have been obtained. The parameters required for the calculations are obtained from the International Reference Ionosphere model and calculated the numerical values of the magnetic field produced by the dynamo current. These calculated values were compared with the magnetic field values measured at Boğaziçi University Kandilli Observatory and Earthquake Research Institute. It was seen that, there was a similarity between the variation of the geomagnetic field and the change of the magnetic field produced by the E-region dynamo current at daytime hours. Especially for the quite days of the sun, it is clear that the change in the east-west component of the geomagnetic field during the daytime hours is caused by the dynamo current of the ionospheric E-region. The magnetic field created by the E-region dynamo current is almost zero at night time hours. The greatest value of the magnetic field produced by the E-region dynamo current was calculated as 47.90 on 21 June, when the the sunspots number maximum. The biggest daily variation in the geomagnetic field was measured as 72 nT on June 21, when the sunspots number was maximum.