Analysis of geomagnetic observatory data and detection of geomagnetic jerks with the MOSFiT software package

Abstract. MOSFiT (Magnetic Observatories and Stations Filtering Tool) is a Python package to visualize and filter data from magnetic observatories and magnetometer stations. The purpose of MOSFiT is to automatically isolate and analyze the secular variation (SV) information measured by geomagnetic observatory data. External field contributions may be reduced by selecting data according to local time and geomagnetic indices and by subtracting the magnetospheric field predictions of the CHAOS-7 model. MOSFiT calculates the SV by annual differences of monthly means, and geomagnetic jerk occurrence time and amplitude are automatically calculated by fitting two straight-line segments in a user-defined time interval of the SV time series. Here, we present the new Python package, validate it against independent results from previous publications and show its application. In particular, we quantify the RMS misfit between SV derived from processing schemes and the SV predicted by CHAOS-7. Analyzing the International Real-time Magnetic Observatory Network (INTERMAGNET) quasi-definitive data with MOSFiT allows for a timely investigation of SV, such as the detection of recent geomagnetic jerks. It can also be used for data selection for, e.g., external field studies or quality control of geomagnetic observatory data.