Fluctuating Geomagnetic Activity: Occurrences and Response of the Magnetospheric Convective Electric Field (MCEF) during the Solar Cycle 24

Abstract

In this paper, we use a statistical approach to study the distribution of days of geomagnetic activity caused by the fluctuation of the Sun’s neutral plate as a function of solar phases and season during solar cycle 24. We also examine the daily response of the magnetospheric convective electric field (MCEF) to the geomagnetic disturbance caused by these days of fluctuating activity. A comparison of the different responses of the MCEF to the three main classes of geomagnetic activity disturbance is also made. A study of the occurrences of fluctuating days shows that: 1) the descending phase is the most active, with an annual occurrence of 50%, followed by the maximum phase (28%), the ascending phase (19%) and finally the ascending phase (15%); 2) spring is the most active season, with an occurrence of 25.55%, followed by autumn (25.25%), summer (24.75%) and winter (24.45%). Irrespective of the phase and time of year, one day in four the Earth’s magnetosphere is under the impact of the fluctuating solar winds responsible for the fluctuating geomagnetic activity. From the minimum phase of the solar cycle to the waning phase, the daily mean values of the MCEF are 0.08448182 mV/m, 0.1134496 mV/m, 0.11846218 mV/m and 0.1178042 mV/m, respectively. The average daily intensities of the MCEF are 0.116947784 mV/m in spring, 0.10854571 mV/m in summer, 0.12374118 mV/m in autumn and 0.10678156 mV/m in winter. Irrespective of solar phase and season, the average daily intensity of the MCEF on fluctuating days is 0.10854945 mV/m. A comparison of the results of this study with previous work on cycle 24 shows that of the three classes of disturbed geomagnetic activity, fluctuating geomagnetic activity is the one that disturbs the magnetospheric convection electric field the least.