349 research outputs found

    A statistical analysis of Pc1–2 waves at a near-cusp station in Antarctica

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    Abstract A statistical study of Pc1–2 waves at southern polar latitudes is presented. Ultra-low frequency geomagnetic field measurements collected at the Italian station Mario Zucchelli (Terra Nova Bay, Antarctica, altitude-adjusted corrected geomagnetic latitude 80°S, MLT = UT − 8) from 2003 to 2010 corresponding with the declining phase of solar cycle 23 and the onset of the solar cycle 24 are used. The long data series allows us to analyze the solar cycle, seasonal and magnetic local time dependence and investigate the possible generation processes related to the solar wind–magnetosphere interaction. We found that during the day, Pc1–2 waves occur around local magnetic noon and midnight. Polarized waves show an almost linear polarization, suggesting a wave propagation along a meridional ionospheric waveguide, from the injection region up to the latitude of Terra Nova Bay. The origin of the waves appears to be due to substorm/stormrelated instabilities and, in the dayside, to solar wind compressions of the magnetopause. Based on these results, we propose a simple model to estimate Pc1–2 power variations depending on geomagnetic activity and solar wind density

    Electromagnetic background noise at L'Aquila Geomagnetic Observatory

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    In this paper we analyze the electromagnetic background noise at L'Aquila Geomagnetic Observatory during 2006 and 2007 in the frequency band 1-100 mHz. In this band a pronounced daily variation is observed both in the natural signals as well as in the artificial ones, giving rise to the problem of separating different contributions of very similar morphology. We analyzed periods when the local K index was approximately zero, in correspondence with minimum of the magnetospheric and ionospheric activity. We found that in our area the main source of artificial noise is constituted by the DC electrified railways

    Local changes in the total electron content immediately before the 2009 Abruzzo earthquake

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    Ionospheric TEC (total electron content) variations derived from GPS measurements recorded at 7 GPS stations in Northern, Central and Southern Italy before and after the 2009 Abruzzo earthquake (EQ) of magnitude Mw6.3 were processed and analyzed. The analysis included interpolated and non-interpolated TEC data. Variations in the TEC of both regional and local characteristics were revealed. Several regional changes were observed in the studied period: 1 January–21 April 2009. After analyzing non-interpolated TEC data of 5 GPS stations in Central Italy (Unpg (Perugia), Untr (Terni), Aqui (Aquila), M0se (Rome) and Paca (Palma Campania, (Naples)), a local disturbance of TEC was also found. This local TEC disturbance arises preparatory to the EQ main shock occurred at 01:32 UT on 06 April 2009, maximizes its amplitude of ~0.8 TECu after the shock moment and disappears after it. The local TEC disturbance was confined at heights below 160 km, i.e. in the lower ionosphere

    Efficient computation of partial elements in the full-wave surface-peec method

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    The partial element equivalent circuit (PEEC) method provides an electromagnetic model of interconnections and packaging structures in terms of standard circuit elements. The surface-based PEEC (S-PEEC) formulation can reduce the number of unknowns compared to the standard volume-based PEEC (V-PEEC) method. This reduction is of particular use in the case of high-speed circuits and high-switching power electronics, where the bandwidth extends from low frequencies to the GHz range. In this article, the S-PEEC formulation is revised and cast in a matrix form. The main novelty is that the interaction integrals involving the curl of the magnetic and electric vector potentials are computed through the Taylor series expansion of the full-wave Green’s function, leading to analytical forms that are rigorously derived. Therefore, the numerical integration is avoided, with a consequent reduction of the computation time. The proposed formulas are studied in terms of the frequency, size of the mesh, and distance between the basis function domains. Three examples are presented, confirming the accuracy of the proposed method compared to the V-PEEC method and surface-based numerical methods from literature

    Geomagnetic field variations at low and high latitude during the January 10-11, 1997 magnetic cloud

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    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

    The 6 April 2009 earthquake at L'Aquila: a preliminary analysis of magnetic field measurements

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    Several investigations reported the possible identification of anomalous geomagnetic field signals prior to earthquake occurrence. In the ULF frequency range, candidates for precursory signatures have been proposed in the increase in the noise background and polarization parameter (i.e. the ratio between the amplitude/power of the vertical component and that one of the horizontal component), in the changing characteristics of the slope of the power spectrum and fractal dimension, in the possible occurrence of short duration pulses. We conducted, with conventional techniques of data processing, a preliminary analysis of the magnetic field observations performed at L'Aquila during three months preceding the 6 April 2009 earthquake, focusing attention on the possible occurrence of features similar to those identified in previous events. Within the limits of this analysis, we do not find compelling evidence for any of the features which have been proposed as earthquake precursors: indeed, most of aspects of our observations (which, in some cases, appear consistent with previous findings) might be interpreted in terms of the general magnetospheric conditions and/or of different sources

    ULF Geomagnetic Pulsations at High Latitudes: the Italian contribution

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    The study of geomagnetic field variations in Antarctica is important in that local field lines are close to extreme magnetospheric regions, such as the polar cusp, where several generation mechanisms for ULF waves are active. Since the eighties, the Italian scientific community developed a research activity in Antarctica at Mario Zucchelli Station (TNB, CGM latitude 80°S), where magnetic facilities are continuously operating. In this review we present the experimental results obtained by a number of investigations conducted in the last years on geomagnetic pulsations in the Pc3-Pc5 frequency range. We also show compared analyses with measurements from other Antarctic and low latitude stations, and, in particular, a statistical analysis of propagation characteristics of low frequency geomagnetic field fluctuations between the two Antarctic stations, TNB and Scott Base

    An approach to estimate carbon stocks change in forest carbon pools under the UNFCCC: the Italian case

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    The 6 April 2009 earthquake at L’Aquila: a preliminary analysis of magnetic field measurements

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    Several investigations reported the possible identification of anomalous geomagnetic field signals prior to earthquake occurrence. In the ULF frequency range, candidates for precursory signatures have been proposed in the increase in the noise background and polarization parameter (i.e. the ratio between the amplitude/power of the vertical component and that one of the horizontal component), in the changing characteristics of the slope of the power spectrum and fractal dimension, in the possible occurrence of short duration pulses. We conducted, with conventional techniques of data processing, a preliminary analysis of the magnetic field observations performed at L’Aquila during three months preceding the 6 April 2009 earthquake, focusing attention on the possible occurrence of features similar to those identified in previous events. Within the limits of this analysis, we do not find compelling evidence for any of the features which have been proposed as earthquake precursors: indeed, most of aspects of our observations (which, in some cases, appear consistent with previous findings) might be interpreted in terms of the general magnetospheric conditions and/or of different sources

    The architectures of translation : a magic carpet-ride through space and time (or, the awkward story of how we dis/placed Krisztina Tóth’s short fiction from Hungarian to English)

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    This interdisciplinary paper unfolds an account of a collaborative translation project, which draws on Ellen Eve Frank’s concept of “literary architecture” to propose a process of “architectural translation”. Our proposal is illustrated by a detailed account of our experiences translating the short fiction of contemporary Hungarian writer, Krisztina Tóth (b. 1967) into English. Staged as a journey through space, time and text, our enquiry frames the process in Barbara Godard’s terms as one of dis/placement, finding resonances with Rosi Braidotti’s nomadic subject and practices of feminist mimesis. Situating Tóth’s fiction in a European feminist literary heritage, we deploy a range of concepts drawn from translation, architecture, literary criticism and feminist philosophy to synthesise a translation strategy which engages the spatial, not only as a metaphor but a methodology for our project. In this account, we propose an architectural methodology as a tool for radical translators, and offer the process of translation as a way of thinking about internal and external spaces in postcolonial contexts
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