Similarities in precursory features in earthquakes and magnetic storms

A basic reason for our interest in complexity is the striking similarity in behavior close to irreversible phase transitions among systems that are otherwise quite different in nature. Earthquakes (EQs) and magnetic storms (MSs) are phenomena involving huge and rapid release of energy characterized by complex temporal occurrence. Herein, by analyzing detected pre-seismic kHz-MHz electromagnetic (EM) emissions on one hand and available experimental Dst catalogues on the other hand, we show that the processes underlying these apparently different phenomena have similar behavior as an EQ or MS approaches. More precisely, by applying wavelet spectral analysis methods we show that distinctive changes in scaling parameters occur as an intense MS or EQ approaches, revealing a gradual reduction of complexity. The emergence of persistent behavior in the tail of the precursory emissions, the significant acceleration of the energy release, i.e., the increase of the susceptibility of the system, the appearance of fluctuations at all scales with simultaneous predominance of large cracks / geomagnetic events, the emergence of strong anisotropy, namely the appearance of preferential direction, may indicate that the generation of an intense EQ or MS becomes, indeed, unavoidable. Interestingly, MHz preseismic EM events / substorm dynamics exhibit anti-persistent behavior and resembles second-order phase transitions, while kHz preseismic EM events / MSs, having persistent behavior, are shown to reveal the features of first-order non-equilibrium phase transitions.