Correlazione Solar Flares e Terremoti

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4. Discussion and conclusions
Herein, the principle of universality in solar flare, magnetic storm and earthquake dynamics is established. The
aforementioned similarity is quantitatively supported by the observation of power-law in the distribution of solar flare and
magnetic storm energy related to a nonextensive Tsallis formalism that gives the Gutenberg–Richter law for the earthquake
magnitude distribution as a special case.
The observed universal dynamics in solar flares, magnetic storms and earthquakes, on the basis of a nonextensive Tsallis
energy distribution function with similar q indices (i.e., 1.82 for flares, 1.84 for storms and 1.6–1.71 for earthquakes),
suggests a common approach to the interpretation of these phenomena in terms of driving physical mechanisms that
have the same character. For instance, de Arcangelis et al. [6] suggested that magnetic stress transfer in the solar corona
plays the role of elastic stress redistribution on the Earth’s crust. On the other hand, plasma pressure distribution in the
inner magnetosphere is one of the key parameters for understanding the development of magnetic storms. Recently,
Tsyganenko [33] demonstrated a dramatic increase of the plasma pressure profiles from quiet to disturbed geomagnetic
conditions. Therefore, plasma pressure redistribution in the Earth’s magnetosphere could play the role of magnetic stress
transfer in the solar corona and elastic stress redistribution on the Earth’s crust.
Solar corona, Earth’s magnetosphere and lithosphere can be considered as externally driven input–output systems. For
the case of solar corona, the generation of active regions is due to the emergence of magnetic flux (i.e., external driver)
to the solar surface. The occurrence of solar flares can be considered as a relaxation process, related to the sudden energy
release of the accumulative free magnetic energy, when a critical value of magnetic field is reached. Similarly the Earth’s
magnetosphere is a system that it is continuously driven externally by the solar wind velocity and magnetic field. Storm
is an interval of time when a sufficiently intense and long-lasting interplanetary convection electric field leads, through a
substantial energization in the magnetosphere–ionosphere system, to an intensified ring current strong enough to exceed
some key threshold of the quantifying storm time Dst index [34]. Lithospheric stress, on the other hand, is increased when
tectonic plates move against each other. When the stress is large enough, the crust is forced to break. Furthermore, the
observation that solar flares and magnetic storms have almost identical q values can be attributed to the fact that both solar
flares and magnetic storms are driven by solar activity.
Recently, De Freitas and De Medeiros [35] used a new approach to study the nonextensivity properties of solar magnetic
activity from 1996–2001. The study was carried out on daily measurements of Sunspot Numbers, mean magnetic-field
strength, and daily means of Total Solar Irradiance. Probability Distribution Functions were calculated for the three datasets
and the obtained results showed that the recently proposed by Tsallis entropic indices (also known as q-Triplet [36]) change
as a function of scale. Moreover, Carvalho et al. [37] applied both Tsallis and Kaniadakis statistics [38,39] to the puzzling
astrophysical problem of the function governing the distribution of stellar rotational velocity. They have shown for the
first time that these are by far the most appropriate statistics for this problem giving a very good fit. It would be of course
interesting and worthwhile to explore those methodologies in the case of solar flares, magnetic storms and earthquakes at
subsequent work.
The evidence of a universal statistical behavior suggests the possibility of a common approach to forecasting of space
weather and earthquakes. In any case, the transfer of ideas and methods of seismic forecasting to the prediction of solar
flares and magnetic storms could improve space weather forecasting.