http://hdl.handle.net/2122/102 Wed, 22 May 2013 04:56:57 GMT 2013-05-22T04:56:57Z http://hdl.handle.net/2122/8598 Title: On the multi-scale nature of large geomagnetic storms: an empirical mode decomposition analysis Authors: De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Consolini, G.; INAF – Istituto di Astrofisica e Planetologia Spaziali, 00133 Roma, Italy; Tozzi, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Complexity and multi-scale are very common properties of several geomagnetic time series. On the other hand, it is amply demonstrated that scaling properties of geomagnetic time series show significant changes depending on the geomagnetic activity level. Here, we study the multiscale features of some large geomagnetic storms by applying the empirical mode decomposition technique. This method, which is alternative to traditional data analysis and is designed specifically for analyzing nonlinear and nonstationary data, is applied to long time series of Sym-H index relative to periods including large geomagnetic disturbances. The spectral and scaling features of the intrinsic mode functions(IMFs) into which Sym-H time series can be decomposed, as well as those of the Sym-H time series itself, are studied considering different geomagnetic activity levels. The results suggest an increase of dynamical complexity and multi-scale properties for intermediate geomagnetic activity levels. Wed, 31 Oct 2012 23:00:00 GMT http://hdl.handle.net/2122/8598 2012-10-31T23:00:00Z http://hdl.handle.net/2122/7443 Title: Anomalies of oxygen measurements performed with Aanderaa optodes Authors: Lo Bue, Nadia; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Editors: Làzaro, Antoni Mànuel; Technical University of Catalonia (UPC) Abstract: Four sets of measurements performed between 2005 and 2010 in the deep central Atlantic, and in deep Mediterranean Sea, and the Arctic Ocean revealed a strange performance of Aanderaa Optode 3830 sensors mounted on RCM11 current meters in low current regimes (current speeds > 10 cm s- 1) . All oxygen data sets collected during these deployments showed significant drops of oxygen (of the order of 50-100 ìmol/l) affecting the Optode data stability in low hydrodynamic conditions (fig.1). High correlations between all acquired parameters (i.e. temperature, turbidity, speed and direction of currents) allowed verifying that no unusual event perturbed the mooring areas during the periods of acquisition, although natural events responsible of so abrupt, short and intense oxygen variations can’t be easily found. Despite the well-known performance of the Aanderaa Optodes, these experiences suggested that the data acquired by optodes installed on RCM11s could not be always reliable, especially in low energy systems (typical for the deep ocean) and that current speeds should always be considered in order to verify the reliability of the data recorded. A series of test in controlled water condition was performed in order to better understand eventual sensor dependence on speed current variations and to evaluate sensor stability in quasi-stationary water. Wed, 21 Sep 2011 22:00:00 GMT http://hdl.handle.net/2122/7443 2011-09-21T22:00:00Z http://hdl.handle.net/2122/7310 Title: Relative ordering in the radial evolution of solar wind turbulence: the S-Theorem approach Authors: Consolini, G.; INAF – Istituto di Fisica dello Spazio Interplanetario, 00133 Roma, Italy; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Over the past few decades scientists have shown growing interest in space plasma complexity and in understanding the turbulence in magnetospheric and interplanetary media. At the beginning of the 1980s, Yu. L. Klimontovich introduced a criterion, named S-Theorem, to evaluate the degree of order in far-from-equilibrium open systems, which applied to hydrodynamic turbulence showed that turbulence flows were more organized than laminar ones. Using the same theorem we have evaluated the variation of the degree of self-organization in both Alfv´enic and non-Alfv´enic turbulent fluctuations with the radial evolution during a long time interval characterized by a slow solar wind. This analysis seems to show that the radial evolution of turbulent fluctuations is accompanied by a decrease in the degree of order, suggesting that, in the case of slow solar wind, the turbulence decays with radial distance. Thu, 22 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/7310 2011-12-22T23:00:00Z http://hdl.handle.net/2122/7166 Title: An information theory approach to the storm‐substorm relationship Authors: De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Consolini, G.; Istituto Nazionale di Astrofisica–Istituto di Fisica dello Spazio Interplanetario, Rome, Italy; Materassi, M.; Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, Sesto Fiorentino, Italy; Tozzi, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: One of the most interesting aspects of the global magnetospheric response to solar wind changes is the relationship between storms and substorms. Here we present new results on the relationship between these two different classes of magnetospheric phenomena by approaching the problem on the side of information theory. Using the Auroral Electrojet AL and SYM‐H indices as representative proxies of magnetic substorms and storms, we investigate the transfer of information by means of transfer entropy analysis (Schreiber, 2000). The obtained results seem, on average, to indicate the presence of a net transfer of information from AL to SYM‐H on time scales shorter than 10 h. On the basis of this result, geomagnetic substorms may act as a driver for the occurrence of geomagnetic storms. However, carrying out a more careful analysis which takes into account the global geomagnetic daily activity, we suggest that the direction of information flow between substorms and storms depends on the global activity level. Indeed, if it is true that a sequence of magnetospheric substorms may drive a moderate storm, it is also true that very large storms may dominate and drive the occurrence of magnetospheric substorms. Fri, 26 Aug 2011 22:00:00 GMT http://hdl.handle.net/2122/7166 2011-08-26T22:00:00Z http://hdl.handle.net/2122/7165 Title: Rank ordering multifractal analysis of the auroral electrojet index Authors: Consolini, G.; INAF-Istituto di Fisica dello Spazio Interplanetario, 00133 Roma, Italy; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: In the second half of the 90s interest grew on the complex features of the magnetospheric dynamics in response to solar wind changes. An important series of papers were published on the occurrence of chaos, turbulence and complexity. Among them, particularly interesting was the study of the bursty and fractal/multifractal character of the high latitude energy release during geomagnetic storms, which was evidenced by analyzing the features of the Auroral Electrojet (AE) indices. Recently, the multifractal features of the small time-scale increments of AE-indices have been criticized in favor of a more simple fractal behavior. This is particularly true for the scaling features of the probability density functions (PDFs) of the AE index increments. Here, after a brief review of the nature of the fractal/multifractal features of the magnetospheric response to solar wind changes, we investigate the multifractal nature of the scaling features of the AE index increments PDFs using the Rank Ordering Multifractal Analysis (ROMA) technique. The ROMA results clearly demonstrate the existence of a hierarchy of scaling indices, depending on the increment amplitude, for the data collapsing of PDFs relative to increments at different time scales. Our results confirm the previous results by Consolini et al. (1996) and the more recent results by Rypdal and Rypdal (2010). Thu, 05 May 2011 22:00:00 GMT http://hdl.handle.net/2122/7165 2011-05-05T22:00:00Z http://hdl.handle.net/2122/6201 Title: The 6 April 2009 earthquake at L’Aquila: a preliminary analysis of magnetic field measurements Authors: Villante, U.; Dipartimento di Fisica, Universit`a L’Aquila, L’Aquila, Italy; De Lauretis, M.; Dipartimento di Fisica, Universit`a L’Aquila, L’Aquila, Italy; De Paulis, C.; Dipartimento di Fisica, Universit`a L’Aquila, L’Aquila, Italy; Francia, P.; Dipartimento di Fisica, Universit`a L’Aquila, L’Aquila, Italy; Piancatelli, A.; Dipartimento di Fisica, Universit`a L’Aquila, L’Aquila, Italy; Piancatelli, A.; Dipartimento di Fisica, Universit`a L’Aquila, L’Aquila, Italy; Pietropaolo, E.; Dipartimento di Fisica, Universit`a L’Aquila, L’Aquila, Italy; Vellante, M.; Dipartimento di Fisica, Universit`a L’Aquila, L’Aquila, Italy; Meloni, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Palangio, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Schwingenschuh, K.; Institut f¨ur Weltraumforschung, Graz, Austria; Prattes, G.; Institut f¨ur Weltraumforschung, Graz, Austria; Magnes, W.; Institut f¨ur Weltraumforschung, Graz, Austria; Nenovski, P.; Geophysical Institute, Sofia, Bulgaria Abstract: 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. Mon, 08 Feb 2010 23:00:00 GMT http://hdl.handle.net/2122/6201 2010-02-08T23:00:00Z http://hdl.handle.net/2122/5984 Title: Application of Autoscala to ionograms recorded by the AIS-Parus ionosonde Authors: Krasheninnikov, I.; Pushkov InstituteofTerrestrialMagnetism,IonosphereandRadiowavePropagation,Russia; Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Scotto, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Autoscala was applied to ionograms recorded by the digital AIS-Parus ionosonde, built at the Pushkov Institute of Terrestrial Magnetism,Ionosphere and Radiowave Propagation, Russia, and installed in Moscow (55.5N,37.5E). Some results in regard to the reliability of the foF2, foF1, and ftEs autoscaled characteristics are presented and discussed. The flexibility of Autoscala is illustrated based on its modular structure. Fri, 30 Apr 2010 22:00:00 GMT http://hdl.handle.net/2122/5984 2010-04-30T22:00:00Z http://hdl.handle.net/2122/5250 Title: COST 296 MIERS: conclusion Authors: Bourdillon, A.; IETR, Université de Rennes 1, France; Cander, L. R.; STFC, Rutherford Appleton Laboratory, Chilton, UK; Zolesi, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: The need for more reliable and efficient communications services, especially those involving ionospheric HF communications and navigational systems, imposes increasing demand for a better knowledge of the effects imposed by the Earth’s upper atmosphere and ways to mitigate disturbing effects. Temporal and spatial changes in the upper atmosphere act to limit and degrade the performance of terrestrial and Earth-space radio systems in many different ways and this is why mitigation activities must involve several topics like ionospheric monitoring and modeling, development of new hardware for communication systems and new propagation simulator, measurements and modeling of ionospheric Total Electron Content (TEC) and ionospheric scintillations, using in particular the Global Positioning System (GPS). The European ionospheric community has long been aware that cooperation research on an international basis is essential to deal with such complex issues. In particular, international cooperation is required for the collection of data, in both the real-time and in retrospective modes, the development and verification of new methods to improve the performance of both operational and future terrestrial and Earth-space communication systems and the exchange of expertise on space plasma effects on Global Navigation Satellite Systems (GNSS). In this context the COST 296 Action MIERS on the «Mitigation of Ionospheric Effects on Radio Systems» has made a significant impact in a number of areas. Fri, 31 Jul 2009 22:00:00 GMT http://hdl.handle.net/2122/5250 2009-07-31T22:00:00Z http://hdl.handle.net/2122/5247 Title: COST 296 MIERS: Mitigation of Ionospheric Effects on Radio Systems Authors: Bourdillon, A.; IETR, Université de Rennes 1, France; Cander, L. R.; STFC, Rutherford Appleton Laboratory, Chilton, UK; Zolesi, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: The COST 296 Action MIERS (Mitigation of Ionospheric Effects on Radio Systems) within the ionospheric community has the objectives, embodied in the Memorandum of Understanding (MoU), to develop an increased knowledge of the effects imposed by the ionosphere on practical radio systems, and the development and implementation of techniques to mitigate the deleterious effects of the ionosphere on such systems. This introductory paper summarizes briefly the background and historical context of COST 296 and outlines the main objectives, working methods and structure. It also lists the participating countries and institutions, the Management Committee (MC) Meetings, the Workshops, Short-term Scientific Missions. In addition, the paper discusses the dissemination activities and the collaboration among the participating institutions and researchers, before outlining the content of the Final Report. Fri, 31 Jul 2009 22:00:00 GMT http://hdl.handle.net/2122/5247 2009-07-31T22:00:00Z http://hdl.handle.net/2122/5241 Title: Ionospheric scintillation monitoring and modelling Authors: Béniguel, Y.; IEEA, Paris, France; Romano, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Alfonsi, Lu.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Aquino, M.; Institute of Engineering Surveying and Space Geodesy, IESSG, Nottingham, UK; Bourdillon, A.; IETR Université de Rennes 1, France; Cannon, P.; Qinetiq, Malvern, UK; De Franceschi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Dubey, S.; DLR, Neustrelitz, Germany; Forte, B.; University of Nova Gorica, Slovenia; Gherm, V.; University of St Petersburg, Russia; Jakowski, N.; DLR, Neustrelitz, Germany; Materassi, M.; Institute for Complex Systems, National Council of Researches, Firenze, Italy; Noack, T.; DLR, Neustrelitz, Germany; Pozoga, M.; Space Research Center, Warsaw, Poland; Rogers, N.; Qinetiq, Malvern, UK; Spalla, P.; Institute for Complex Systems, National Council of Researches, Firenze, Italy; Strangeways, H. J.; School of Electronic and Electrical Engineering, University of Leeds, UK; Warrington, E. M.; Department of Engineering, University of Leicester, UK; Wernik, A.; Space Research Center, Warsaw, Poland; Wilken, V.; DLR, Neustrelitz, Germany; Zernov, N.; University of St Petersburg, Russia Abstract: This paper presents a review of the ionospheric scintillation monitoring and modelling by the European groups involved in COST 296. Several of these groups have organized scintillation measurement campaigns at low and high latitudes. Some characteristic results obtained from the measured data are presented. The paper also addresses the modeling activities: four models, based on phase screen techniques, with different options and application domains are detailed. Finally some new trends for research topics are given. This includes the wavelet analysis, the high latitudes analysis, the construction of scintillation maps and the mitigation techniques. Fri, 31 Jul 2009 22:00:00 GMT http://hdl.handle.net/2122/5241 2009-07-31T22:00:00Z