Latitudinal dependence of Pc3-4 amplitudes across the dip equator along the 210º Magnetic Meridian

Abstract

Studying Pc3-4 geomagnetic pulsations at equatorial and very low latitude regions is an important issue to understand their generation and propagation mechanisms. Pc3-4 amplitudes and their latitudinal dependency across the dip equator up to low latitudes (± 25°) are investigated using geomagnetic data simultaneously obtained by the MAGDAS/CPMN stations along the 210° Magnetic Meridian (MM) chain. Forty-five Pc3 events and thirty-two Pc4 events were selected for this study. Our results show a clear dependence of Pc3-4 amplitudes on geomagnetic latitudes. At the dip equator, most of the selected Pc3 events (~75%) showed an enhancement in amplitudes, while the rest (~25%) showed an attenuation. After that, the amplitudes decreased gradually by increasing latitudes. These results suggest mixed generation and propagation mechanisms for the equatorial and very low latitudes Pc3s. For better understanding, the Interplanetary Magnetic Field (IMF) and solar conditions are examined during the selected events. Results indicate that Pc3 events with enhanced amplitudes at dip equator are mainly occurred in daytime with no preference to IMF (magnitude and direction) and solar parameters, which suggests the ionospheric currents model as a generation and propagation mechanism for these events. While the attenuation observed in the other Pc3 events was associated with intense and abrupt fluctuations in the IMF and solar parameters, which in turn suggests the compressional wave model for generating these Pc3 events. On the other hand, these two models can explain the observed enhancement in the Pc4 amplitudes at the dip equator. Therefore, our obtained results clarified the origin of equatorial Pc3-4 pulsations.