Statistical study of magnetic disturbances at the Earth's surface

We analyzed a series of records acquired at the Vassouras National Geomagnetic Observatory in Brazil for the month of October 2000. We report the power laws and relevant distributions of magnetic field intensities, duration of disturbed periods, and the elapsed time between consecutive disturbed periods. The observed double power laws that we have found illustrate special characteristics of the magnetic field sources. In particular, they could be pointing to a threshold system as the source for such perturbations. Threshold values for the transition between two power-law regimes in both duration and intensity of disturbances distributions, as well as their interconnection are highlighted. The work also includes an (up to our knowledge) original procedure to isolate higher frequencies in the time domain. Some possible trends for future works are advanced.