http://hdl.handle.net/2122/107 Tue, 21 May 2013 05:33:51 GMT 2013-05-21T05:33:51Z http://hdl.handle.net/2122/4545 Title: Crustal structure in the Southern Apennines from teleseismic receiver functions Authors: Steckler, M. S.; Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York; Piana Agostinetti, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Wilson, C. K.; Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York; Roselli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Seeber, L.; Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York; Amato, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Lerner-Lam, A.; Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York Abstract: While the upper crustal structure of the Southern Apennines is known, lack of control on the deep structure allows competing thin-skinned and thick-skinned models of the orogen. In thin-skinned models, the detachment decouples a stack of rootless nappes from the basement. In thick-skinned models, basement is involved in the most recent phase of thrusting. To examine crustal structure, we use teleseismic data from the Calabria-Apennine-Tyrrhenian/Subduction- Accretion-Collision Network (CAT/SCAN) array in southern Italy. We use receiver functions (RF) processed into a common conversion point stack to generate images of the crust. Inter- pretation and correlation to geological structure are done using inversions of individual station RFs. We focus on a shallow discontinuity where P-to-S conversions occur. In the foreland, it corresponds to velocity jumps between carbonate and clastic strata with basement. A similar interpretation for the Apennines provides the most parsimonious explanation and supports a thick-skinned interpretation. In a thick-skinned reconstruction, the amount of shortening is much smaller than for a thin-skinned model. This implies considerably less Pliocene–Pleistocene shortening across the Apennines and suggests an east-southeast motion of the Calabrian arc subparallel to the southern Apennines rather than a radial expansion of the arc. Thu, 31 Jan 2008 23:00:00 GMT http://hdl.handle.net/2122/4545 2008-01-31T23:00:00Z http://hdl.handle.net/2122/4530 Title: Understanding crust dynamics and subduction in southern Italy Authors: Margheriti, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia Abstract: To mark the centennial anniversary of the 1908 earthquake that shook Messina, Italy, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) began the “Messina 1908–2008” research project. The aim is to clarify the extension deformation processes that occur in the Strait of Messina and to understand relationships between subduction and crustal deformation there by merging existing data and studies, and by collecting new and more detailed seismological, geodetic, historical, and satellite observations. Mon, 16 Jun 2008 22:00:00 GMT http://hdl.handle.net/2122/4530 2008-06-16T22:00:00Z http://hdl.handle.net/2122/4072 Title: A Revised Forest Fire Model Non-Quasistatically Driven for the Sporadic Activity of the Earth’s Magnetotail Authors: De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Consolini, G.; Istituto di Fisica dello Spazio Interplanetario, CNR, Via Fosso del Cavaliere 100, 00133 Roma, Italy Editors: Sawaya-Lacoste, H.; ESA Publications Division Abstract: The energy release during magnetospheric substorms in response to solar wind changes consists of two main physical processes: the directly-driven and the unloading processes. Recent analysis on the sporadic activity related to the unloading process seems to indicate that the magnetospheric response to solar wind changes might resemble the behaviour of an out-of-equilibrium system near a marginally stable point (critical point). Here, we present a modified version of the well-known forest-fire cellular automaton (FFM) not quasistatically driven for the sporadic activity of the energy release in the geotail regions as revealed by the auroral electrojet index. Thu, 31 Jan 2002 23:00:00 GMT http://hdl.handle.net/2122/4072 2002-01-31T23:00:00Z http://hdl.handle.net/2122/4026 Title: On the Earth’s magnetospheric dynamics: Nonequilibrium evolution and the fluctuation theorem Authors: Consolini, G.; Istituto di Fisica dello Spazio Interplanetario, INAF, Rome, Italy; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Tozzi, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: The Earth’s magnetosphere evolves as an out-of-equilibrium system due to the continuous coupling with the solar wind and the Earth’s ionosphere. We test the validity of the symmetries implied in the Fluctuation Theorem for the magnetospheric dynamics by investigating the long-term evolution of the Earth’s magnetospheric ring current, as monitored by the geomagnetic Dst index. We find that the symmetries implied by the Fluctuation Theorem are all verified, thus providing a proof of the existence of a steady state far from equilibrium for the Earth’s magnetosphere. A possible link between the Dst index and the entropy production rate is also proposed and discussed. Wed, 20 Aug 2008 22:00:00 GMT http://hdl.handle.net/2122/4026 2008-08-20T22:00:00Z http://hdl.handle.net/2122/4023 Title: Fractal time statistics of AE-index burst waiting times: evidence of metastability Authors: Consolini, G.; Istituto di Fisica dello Spazio Interplanetario – CNR, Roma, Italy; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Recent observations and analyses evidenced that the magnetotail, as well as the magnetospheric dynamics are characterised by a scale-free behaviour and intermittence. These results, along with numerical simulations on cellular automata, suggest that the observed scale-invariance may be due to forced and/or self-organised criticality (FSOC), meaning that the magnetotail operates near a marginally stable state (Chang, 1999). On the other hand, it was underlined that a complex magnetic field topology in the geotail regions may play a relevant role in the impulsive energy relaxation (Consolini and Chang, 2001). Mon, 31 Dec 2001 23:00:00 GMT http://hdl.handle.net/2122/4023 2001-12-31T23:00:00Z http://hdl.handle.net/2122/4022 Title: A revised forest-fire cellular automaton for the nonlinear dynamics of the Earth’s magnetotail Authors: Consolini, G.; Istituto di Fisica dello Spazio Interplanetario, Consiglio Nazionale delle Ricerche-CNR, Via Fosso del Cavaliere 100, 00133 Roma, Italy; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Recent observations and numerical simulations seem to suggest that the Earth’s magnetotail plasma could exist in a near-criticality configuration, and that many features of the magnetospheric response to solar wind changes could be described by avalanche models displaying self-organized criticality. Further evidences of this near-criticality dynamics have been found analyzing the statistical features of the auroral electrojet (AE) index. Here, we present a cellular automaton, based on a revised version of the well-known forest-fire model, for the nonlinear dynamics of the Earth’s magnetotail. This simple model, chaotically driven using a 1-d coupled map, is able to capture many of the statistical features of the magnetospheric response to solar wind changes. The results, compared with previous analyses of the AE-index features, are discussed in the framework of a near-criticality dynamics of the magnetospheric tail plasma. Fri, 31 Aug 2001 22:00:00 GMT http://hdl.handle.net/2122/4022 2001-08-31T22:00:00Z http://hdl.handle.net/2122/3934 Title: The Earth's passage of the April 11, 1997 coronal ejecta: geomagnetic field fluctuations at high and low latitude during northward interplanetary magnetic field conditions Authors: Lepidi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Francia, P.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Villante, U.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Meloni, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Lazarus, A. J.; Center for Space Research, MIT, Cambridge, USA; Lepping, R. P.; Laboratory for Extraterrestrial Physics, NASA/GSFC, Greenbelt, USA Abstract: An analysis of the low frequency geomagnetic field fluctuations at an Antarctic (Terra Nova Bay) and a low latitude (L'Aquila, Italy) station during the Earth's passage of a coronal ejecta on April 11, 1997 shows that major solar wind pressure variations were followed at both stations by a high fluctuation level. During northward interplanetary magnetic field conditions and when Terra Nova Bay is close to the local geomagnetic noon, coherent fluctuations, at the same frequency (3.6 mHz) and with polarization characteristics indicating an antisunward propagation, were observed simultaneously at the two stations. An analysis of simultaneous measurements from geosynchronous satellites shows evidence for pulsations at approximately the same frequencies also in the magnetospheric field. The observed waves might then be interpreted as oscillation modes, triggered by an external stimulation, extending to a major portion of the Earth's magnetosphere. Thu, 31 Dec 1998 23:00:00 GMT http://hdl.handle.net/2122/3934 1998-12-31T23:00:00Z http://hdl.handle.net/2122/3933 Title: Polarization pattern of low-frequency geomagnetic field fluctuations (0.8-3.6 mHz) at high and low latitude Authors: Lepidi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Francia, P.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Villante, U.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Lanzerotti, L. J.; Bell Laboratories, Lucent Technologies, Murray Hill, New Jersy; Meloni, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: A statistical analysis of the polarization pattern of low-frequency geomagnetic field fluctuations (0.8-3.6 mHz) covering the entire 24-hour interval has been performed at an Antarctic station (Terra Nova Bay) and a low-latitude station (L'Aquila, Italy) during the entire 1995. The results show a complex pattern in which, in agreement with predictions, four polarization reversals occur at high latitude during the local day. A comparison with another Antarctic station, McMurdo, during a shorter interval in 1994 confirms these results. At low latitude the polarization sense in the afternoon reverses with respect to the morning, but the reversal is delayed by a few hours after the expected local noon. In Antarctica the polarization pattern does not show any dependence on frequency and season, while at L'Aquila it is better defined for frequencies below ≈2 mHz and during local summer. Thu, 31 Dec 1998 23:00:00 GMT http://hdl.handle.net/2122/3933 1998-12-31T23:00:00Z http://hdl.handle.net/2122/3932 Title: Pc3 pulsations during variable IMF conditions Authors: Villante, U.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Lepidi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Francia, P.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Vellante, M.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Meloni, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Lepping, R. P.; Laboratory for Extraterrestrial Physics, NASA/GSFC, Greenbelt, USA; Mariani, F.; Dipartimento di Fisica, Università di Roma-Tor Vergata, Italy Abstract: Pc3 geomagnetic field fluctuations detected at low latitude (L'Aquila, Italy) during the passage of a high velocity solar wind stream, characterized by variable interplanetary magnetic field conditions, are analyzed. Higher frequency resonant fluctuations and lower frequency phenomena are simultaneously observed; the intermittent appearance and the variable frequency of the longer period modes can be well interpreted in terms of the variable IMF elements; moreover their polarization characteristics are consistent with an origin related to external waves propagating in antisunward direction. A comparison with simultaneous observations performed at Terra Nova Bay (Antarctica) provides additional evidence for a clear relationship between the IMF and Pc3 pulsations also at very high latitudes. Thu, 31 Dec 1998 23:00:00 GMT http://hdl.handle.net/2122/3932 1998-12-31T23:00:00Z http://hdl.handle.net/2122/3931 Title: Geomagnetic field variations at low and high latitude during the January 10-11, 1997 magnetic cloud Authors: Villante, U.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Francia, P.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Lepidi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; De Lauretis, M.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Pietropaolo, E.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Cafarella, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Meloni, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Lazarus, A. J.; Center for Space Research, MIT, Cambridge, USA; Lepping, R. P.; Lab. for Extraterrestrial Physics, NASA/GSFC, Greenbelt, USA; Mariani, F.; Dipartimento di Fisica, Università di Roma-Tor Vergata, Italy Abstract: On Jan. 10-11, 1997 a wide magnetic cloud reached the Earth triggering intense geomagnetic activity. Observations performed at low and very high latitude show that the same features appear simultaneously in correspondence to different changes in the solar wind conditions. In particular, highly polarized modes are simultaneously observed at the same discrete frequencies after the passage of the high density solar wind region following the cloud. SI's and ULF waves polarization are also examined in a wide latitudinal and longitudinal extent. Tue, 14 Jul 1998 22:00:00 GMT http://hdl.handle.net/2122/3931 1998-07-14T22:00:00Z