Distinct responses of the low-latitude ionosphere to CME and HSSWS: The role of the IMF B^z oscillation frequency

International audienceIn this work an attempt to identify the role of the interplanetary magnetic field (IMF) in the response of the ionosphere to different solar phenomena is presented. For this purpose, the day-today variability of the equatorial ionospheric anomaly (EIA) and the main ionospheric disturbances are analyzed during one coronal mass ejection (CME) and two high-speed solar wind streams (HSSWSs). The EIA parameters considered are the zonal electric field and both the strength and position of its northern crest. The disturbances being the prompt penetration of magnetospheric electric field (PPMEF) and disturbance dynamo electric field (DDEF) are studied using the magnetic response of their equivalent current systems. In accordance, ground-based Global Navigation Satellite Systems receivers and magnetometers at geomagnetic low latitudes in the American sector are used. During both phenomena, patterns of PPMEF related to fluctuations of the IMF are observed. Diurnal and semidiurnal magnetic oscillations are found to be likely related to DDEF. Comparisons among the EIA parameters and the DDEF magnetic response exhibit poor relation during the CME in contrast to good relation during the HSSWSs. It is concluded that the response of the low-latitude ionosphere to solar phenomena is largely determined through the oscillation frequency of the IMF B z by affecting the generation of the PPMEF and DDEF differently. This is seen as an effect of how the energy from the solar wind is transferred into the magnetosphere-ionosphere system