Statistical study of the DP2 enhancement at the dayside dip-equator compared to low latitudes

International audienceIt has been largely investigated and established that the DP2 events are enhanced at dip-equator compared to low latitudes. Studies by several authors showed various enhancement ratio values of DP2 amplitude at the dayside dipequator relative to those at low latitudes. In order to quantify this enhancement ratio, we carried out a statistical study on this phenomenon using the ground magnetometer data at locations ranging from polar cap to dip-equator over the African, Asian and American sector. Our result gave an enhancement ratio which shows a diurnal variation with a maximum value around 12:00 LT and is correlated with the regular variation of the geomagnetic H-component. The longitudinal variation of the enhancement ratio of the DP2 exhibits high values over the American sector compared to Asian sector and African sector which have lowest values. This longitudinal dependence is similar to that of the equatorial electrojet magnetic effect

Simulation of electric field and current during the 11 June 1993 disturbance dynamo event: Comparison with the observations

International audienceThe ionospheric disturbance dynamo signature in geomagnetic variations is investigated using the National Center for Atmospheric Research Thermosphere‐ Ionosphere‐Electrodynamics General Circulation Model. The model results are tested against reference magnetically quiet time observations on 21 June 1993, and disturbance effects were observed on 11 June 1993. The model qualitatively reproduces the observed diurnal and latitude variations of the geomagnetic horizontal intensity and declination for the reference quiet day in midlatitude and low‐latitude regions but underestimates their amplitudes. The patterns of the disturbance dynamo signature and its source "anti‐Sq" current system are well reproduced in the Northern Hemisphere. However, the model significantly underestimates the amplitude of disturbance dynamo effects when compared with observations. Furthermore, the largest simulated disturbances occur at different local times than the observations. The discrepancies suggest that the assumed high‐latitude storm time energy inputs in the model were not quantitatively accurate for this storm