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Quantifying the EEJ current with ground-based ionosonde inferred vertical E × B drifts in the morning hours over Ilorin, West Africa

Adeniyi J.O., Adimula I.A., Adebesin B.O, Reinisch B.W., Oladipo O.A., Olawepo O., Yumoto K.

Acta Geophysica

2014

Vol. 62, no. 3

656--678

The relationship between the ground-based inferred vertical E × B drifts, Vz, and the magnetic equatorial electrojet current during the year of solar minima was presented. Both the diurnal and seasonal Vz variations are positively directed during the daytime and negative at nighttime. The evening time pre-reversal enhancement occurs around 19:00 LT. The fairly strong linear relationship between the electrojet current strength and Vz exhibited higher correlations during the daytime (06:00-16:00 LT). The maximum morning time proxy parameter described by E = [d (ΔHILR)/dt]max in the morning hours, indicating the east-west electric field in the EEJ, corresponds reasonably well with the E × B drift and, hence, can be used as a proxy parameter for representing Vz in the morning hours. The daytime EEJ magnitude seasonal changes are connected with a change in conductivity emerging from the action of turbulence and divergence of momentum flux. These waves above the dynamo region are suggested to lead to partial counter electrojet during the equinoctial months.

Fractal characteristics of the ULF emissions along a meridian profile, based on the 210 MM stations data

Varlamov A., Smirnova N., Hayakawa M., Yumoto K.

Acta Geophysica

2012

Vol. 60, no. 3

928-941

Fractal analysis of magnetic records (1 Hz sampling rate) of 5 stations (Guam, Moshiri, Paratunka, Magadan, and Chokurdakh) located along the 210 magnetic meridian (210 MM) has been performed using the Higuchi method. The period of 22 months (October 1992 to July 1994) that embodies the date of the strong Guam earthquake of 8 August 1993 has been considered. A comparison of the ULF emissions scaling parameters (spectral exponents β and fractal dimensions D) obtained at different latitudes has been made. Dependence of β and D on the Kp index of geomagnetic activity has been analyzed for each of the 24 local time intervals. It is revealed that D decreases (β increases) with increasing geomagnetic activity at all stations, but the rates of decrease (increase) are different at different stations and in different time intervals. It is shown that the evening, night and early morning hours are preferable to study magnetospheric effects, whereas the noon hours are the most suitable for the analysis of lithospheric effects. A possibility of using the data of the 210 MM stations as reference materials for the Guam seismically active area is discussed.