Structure and properties of the Adriatic crust in the central‐eastern Southern Alps (Italy) from local earthquake tomography

Structure and properties of the Adriatic crust were determined from local earthquake tomography around the Giudicarie fault zone (central‐eastern Southern Alps, Italy). Tomographic results, based on well‐suited 436 revised earthquakes (period 1994–2007), have a resolution comparable to the scale of regional geological domains and tectonic structures. The observed strong velocity anomalies correlate well with lithological variations corresponding to different geological domains (particularly magmatic complexes at depth) and with high fracturing and/or presence of fluids along active fault systems (South Giudicarie and Valsugana–Bassano del Grappa–Montello thrusts).     

Solar Dynamo and Toroidal Field Instabilities

The possibility of non-axisymmetric (kink) instabilities of a toroidal field seated in the tachocline is much discussed in the literature. In this work, the basic properties of kink and quasi-interchange instabilities, produced by mixed toroidal and poloidal configuration, will be briefly reviewed. In particular, it will be shown that the unstable modes are strongly localized near the Equator and not near the Poles as often claimed in the literature. Based on the results of recent numerical simulations, it is argued that a non-zero helicity can already be produced at a non-linear level. A mean-field solar dynamo is then constructed with a positive α-effect in the overshoot layer localized near the Equator, and a meridional circulation with deep return flow. Finally, the possibility that the solar cycle is driven by an αΩ dynamo generated by the negative subsurface shear in the supergranulation layer will also be discussed.