A software to extract time series from historical magnetograms

International audience or nearly a century, magnetogram have been recorded on paper sheets. Numerical valueswere collected into tables, usually with a sampling of one hour. Today, most of these tableshave been digitised and disseminated through national or international data services.A large collection of photographic paper magnetograms, covering globally an entire centuryis preserved in the archives of Chambon-la-forêt magnetic observatory, France. It containsmagnetograms from the Mascart and La Cour magnetometer, and from several otherobservatories in France, Africa and Polynesia.In order to access additional information on the magnetic variations recorded on themagnetograms, we developed a recovering software: RECOV. It is based on MATLAB and canbe run either as a MATLAB App, or as a standalone desktop application, with MATLABRuntime. It provides an interface for manual selection of magnetic traces that are convertedinto magnetic variations and calibrated time series, if definitive hourly time series areavailable. The user can recover magnetograms of different quality, even cases when themagnetic traces cross the temporal axis, or wrap-around traces appear during the strongeststorms. We aim obtaining recovered time-series with sampling every minute, with a reliabilitydepending on the size and resolution of magnetic traces. We present this software and someexamples of the obtained time series.