Mansilla, G. A.

In this article, we present a study of the perturbations occurring in the Earth’s environment on 7 October 2015. We use a multi-instrument approach, including space and ground observations. In particular, we study the ionospheric conditions at low latitudes. Two ionospheric storms are observed at the low latitude station of Tucumán (26° 51' S, 65° 12' W). We observe a negative ionospheric storm followed by a positive one. These ionospheric perturbations were triggered by two sudden storm commencements (SSCs) of a strong geo-magnetic storm. Preliminary results show that the main mechanism involved in both ionospheric storms is the prompt penetration of electric fields (PPEFs) from the magnetosphere. Furthermore, in the positive storm, disturbed dynamo electric fields are observed acting in combination with the PPEFs. The impact of the solar wind on the Earth’s environment is analyzed using geomagnetic data and proxies, combined with data acquired in the Tucumán Low Latitude Observatory for the Upper Atmosphere. We also investigate the solar and interplanetary drivers of this intense perturbation. We find that, although typically interplanetary coronal mass ejections (ICMEs) are the most geoeffective transient interplanetary events, in this case, a corotating interaction region (CIR) is responsible for these strong perturbations to the geospace.

Neutral wind effects in the F2-region during geomagnetic storms are theoretically studied solving the continuity equation (with production and loss of electrons) by means of a numerical method. This study was made for storms with sudden commencement at different times of day and at different latitudes. The results show that the equatorward movements of neutral air produce either enhanced or depressed maximum electron density values which depend on the velocity of these winds when the perturbation occurs at diurnal hours. If the geomagnetic storm is present during the night, only enhanced values are observed.