The RALMAG magnetometer manufactured by RadioAstroLab uses a fluxgate sensor and is sensitive only to transient variations of the Earth's magnetic field (i.e. those with a duration of the order of seconds or tens of minutes), not to daily thermal drifts or long-term variations . It is these rapid fluctuations that in fact characterize the initial phase of a geomagnetic storm, which is an event that can cause significant damage to electrical and electronic systems, if of high intensity. It is known from the literature that past episodes of astrophysical events originating on the Sun (solar flares, coronal mass expulsions) and transferred from the solar wind to the magnetosphere, have generated geomagnetic storms with consequences on a planetary scale, not only technological but also social. In order to interpret as important as possible the important variations in the horizontal components of the local geomagnetic field, and to link them to the activity of the Sun, it is essential that the measuring instrument is installed in a "quiet" location, that is far from artificial interference and anthropic, which is buried to minimize the effects of daily thermal fluctuations on the measurement and which is connected to a central unit for acquisition and to a computer connected to the internet. A specially developed program processes the measurements representing the daily variations of the geomagnetic field which will be compared with the measurements performed by the reference observatories. In this way you have an excellent tool to observe the "invisible disturbed" Sun, correlating the effects of its activity on the magnetosphere with the visible signs that we observe directly on the disk (photosphere - chromosphere).