A New Open‐Source Geomagnetosphere Propagation Tool (OTSO) and Its Applications

We present a new open‐source tool for magnetospheric computations, that is modeling of cosmic ray (CR) propagation in the geomagnetosphere, named “Oulu—Open‐source geomagneToSphere prOpagation tool” (OTSO), available on GitHub ( https://github.com/NLarsen15/OTSO ) and Zenodo ( https://doi.org/10.5281/zenodo.7516233 ). A tool of this nature is required in order to interpret experiments and study phenomena within the CR research field. Within this work, OTSO is applied to the investigation of several ground‐level enhancement events. Here, we demonstrated several applications of OTSO, namely the computation of asymptotic directions of selected CR stations, effective rigidity cut‐off across the globe at various conditions within the design, and general properties, including the magnetospheric models employed. Comparison and validation of OTSO with older widely used tools such as MAGNETOCOSMICS was performed, and good agreement was achieved. An application of OTSO for providing the necessary background for the analysis of two notable ground‐level enhancements is demonstrated and their spectral and angular characteristics are presented.