Evidences of a threshold system as the source for magnetic storms detected on Earth s surface

Threshold systems appear to underlie the global behaviour of physical phenomena very unlike at a first look. The usual experimental fingerprint of threshold system grounded phenomena is the presence of power laws. Experimental evidence has been found, for example, in superconductor vortex avalanches, sand piles, the brain, 4He superfluidity and earthquakes. Double power-laws have been found in social networks, in the luminosity of some galactic nuclei and, very recently, in solar flares, among others. Here we show evidences that point to a threshold system as the source for magnetic storms detected on the Earth. We based our analysis on series of data acquired during many years in the network of magnetic observatories of the National Observatory (Brazil). In particular we focused our attention on October 2000 month of the Vassouras Observatory (RJ, Brazil), which have been active since 1915. We have found both power laws and double power laws for some relevant distributions.