http://hdl.handle.net/2122/106 Ricerca nel canale cerca http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/5019 Titolo: Monitoring the Dynamics of the Ionosphere–Plasmasphere System by Ground-Based ULF Wave Observations<br/><br/>Autori: Vellante, M.; Dipartimento di Fisica, Università dell’Aquila, L’Aquila, Italy; Förster, M.; GeoForschungsZentrum, Potsdam, Germany; Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Jakowski, N.; Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Kommunikation und Navigation, Neustrelitz, Germany; Zhang, T. L.; Institut für Weltraumforschung, Graz, Austria; Villante, U.; Dipartimento di Fisica, Università dell’Aquila, L’Aquila, Italy; De Lauretis, M.; Dipartimento di Fisica, Università dell’Aquila, L’Aquila, Italy; Zolesi, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Magnes, W.; Institut für Weltraumforschung, Graz, Austria<br/><br/>Abstract: Cross-spectral analysis of ULF wave measurements recorded at ground magnetometerstations closely spaced in latitude allows accurate determinations ofmagnetospheric field line resonance (FLR) frequencies. This is a useful tool for remotesensing temporal and spatial variations of the magnetospheric plasma mass density. Thespatial configuration of the South European GeoMagnetic Array (SEGMA, 1.56 < L <1.89) offers the possibility to perform such studies at low latitudes allowing to monitor thedynamical coupling between the ionosphere and the inner plasmasphere. As an example ofthis capability we present the results of a cross-correlation analysis between FLR frequenciesand solar EUV irradiance (as monitored by the 10.7-cm solar radio flux F10.7)suggesting that changes in the inner plasmasphere density follow the short-term (27-day)variations of the solar irradiance with a time delay of 1–2 days. As an additional examplewe present the results of a comparative analysis of FLR measurements, ionospheric verticalsoundings and vertical TEC measurements during the development of a geomagneticstorm. http://hdl.handle.net/2122/4072 Titolo: A Revised Forest Fire Model Non-Quasistatically Driven for the Sporadic Activity of the Earth’s Magnetotail<br/><br/>Autori: 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<br/><br/>Curatori: Sawaya-Lacoste, H.; ESA Publications Division<br/><br/>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 activityrelated 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. http://hdl.handle.net/2122/4026 Titolo: On the Earth’s magnetospheric dynamics: Nonequilibrium evolution and the fluctuation theorem<br/><br/>Autori: 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<br/><br/>Abstract: The Earth’s magnetosphere evolves as an out-of-equilibrium system due to thecontinuous 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 byinvestigating the long-term evolution of the Earth’s magnetospheric ring current, asmonitored by the geomagnetic Dst index. We find that the symmetries implied by theFluctuation 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. http://hdl.handle.net/2122/4023 Titolo: Fractal time statistics of AE-index burst waiting times: evidence of metastability<br/><br/>Autori: Consolini, G.; Istituto di Fisica dello Spazio Interplanetario – CNR, Roma, Italy; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia<br/><br/>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 maybe due to forced and/or self-organised criticality (FSOC), meaning that the magnetotail operates near a marginally stablestate (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). http://hdl.handle.net/2122/4022 Titolo: A revised forest-fire cellular automaton for the nonlinear dynamics of the Earth’s magnetotail<br/><br/>Autori: 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<br/><br/>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. http://hdl.handle.net/2122/3983 Titolo: Long period geomagnetic field fluctuations at Terra Nova Bay (Antarctica)<br/><br/>Autori: Villante, U.; Dipartimento di Fisica, Università dell'Aquila, L’Aquila, Italy; Lepidi, S.; Dipartimento di Fisica, Università dell'Aquila, L’Aquila, Italy; Francia, P.; Dipartimento di Fisica, Università dell'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<br/><br/>Abstract: A statistical analysis of the power spectra (0.7 - 5 mHz) of the geomagnetic field components H and D recorded at Terra Nova Bay (Antarctica) during three austral summers close to the maximum of solar activity reveals power enhancements in the H componenta t = 3.3, 3.9 and 4.5 mHz, which become more evident during daytime intervals. During intervals characterized by higher solar wind speeds these spectral features more clearly emerge and are also accompaniedby other enhancements at lower frequencies (= 1.2, 1.9 and 2.7 mHz). The observed frequencies are close to the ones detected both at auroral and low latitudes. http://hdl.handle.net/2122/3908 Titolo: Low frequency geomagnetic field variations at Dome C (Antarctica)<br/><br/>Autori: Lepidi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cafarella, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Francia, P.; Dipartimento di Fisica, Università dell’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; Schott, J. J.; EOST, IPG, Strasbourg, France<br/><br/>Abstract: We conduct an analysis of the geomagnetic field variations recorded at the new Antarctic station Dome C, located very close to the geomagnetic pole, which has been operating for approximately one month during the 1999–2000 campaign. We also perform a comparison with simultaneous measurements at the Italian Antarctic station Terra Nova Bay, in order to investigate the spatial extension of the phenomena observed at very high latitude. Our results show that between the two stations the daily variation is similar and the fluctuations with f 1 mHz are coherent, provided that in both cases the comparison is made between geographicallyoriented components, suggesting that ionospheric currents related to the geographic position, more than field-alignedcurrents, are responsible for the lowest frequency variations; conversely, higher frequency (Pc5) fluctuations are substantially decoupled between the two stations. We also found that at Dome C the fluctuation power in the 0.55–6.7 mHzfrequency band is well related with the solar wind speed during the whole day and that at Terra Nova Bay the correlation is also high, except around local geomagnetic noon, when the station approaches the polar cusp. These results indicate that the solar wind speed control of the geomagnetic field fluctuationpower is very strict in the polar cap and less important close to the polar cusp. http://hdl.handle.net/2122/3084 Titolo: Propagation of low frequency geomagnetic field fluctuations in antarctica: comparison between two polar cap stations<br/><br/>Autori: Santarelli, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Lepidi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cafarella, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia<br/><br/>Abstract: We conduct a statistical analysis of the coherence and phase difference of low frequency geomagnetic fluctuationsbetween two Antarctic stations, Mario Zucchelli Station (geographic coordinates: 74.7 S, 164.1 E; correctedgeomagnetic coordinates: 80.0 S, 307.7 E) and Scott Base (geographic coordinates: 77.8 S 166.8 E; corrected geomagneticcoordinates: 80.0 S 326.5 E), both located in the polar cap. Due to the relative position of the stations, whose displacement is essentially along a geomagnetic parallel, thephase difference analysis allows to determine the direction of azimuthal propagation of geomagnetic fluctuations. Theresults show that coherent fluctuations are essentially detectable around local geomagnetic midnight and, in a minorextent, around noon; moreover, the phase difference reverses in the night time hours, indicating a propagation directionaway from midnight, and also around local geomagnetic noon, indicating a propagation direction away from the subsolarpoint. The nigh time phase reversal is more clear for southward interplanetary magnetic field conditions, suggestinga relation with substorm activity.The introduction, in this analysis, of the Interplanetary Magnetic Field conditions, gave interesting results, indicatinga relation with substorm activity during nighttime hours. We also conducted a study of three individual pulsationevents in order to find a correspondence with the statistical behaviour. In particular, a peculiar event, characterizedby quiet magnetospheric and northward interplanetary magnetic field conditions, shows a clear example of waves propagatingaway from the local geomagnetic noon; two more events, occurring during southward interplanetary magnetic field conditions, in one case even during a moderate storm,show waves propagating away from the local geomagnetic midnight. http://hdl.handle.net/2122/3083 Titolo: Low frequency geomagnetic field fluctuations at cap and low latitude during October 29-31, 2003<br/><br/>Autori: Lepidi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cafarella, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Santarelli, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia<br/><br/>Abstract: On October-November 2003 complex interplanetary structures, originated by a series of solar eruptions, hit the Earth, triggering violent Sun-Earth connection events. In this paper we analyze the low frequency geomagnetic field fluctuations detected on the ground during Oct. 29-31, 2003, a time period characterized by extremely high solar wind speed values and by out-of-ecliptic interplanetary magnetic field orientation for intervals of several hours. We analyze geomagnetic field measurements at four high latitude stations located in the polar cap, three in the southern and one in the northern hemisphere. From a comparison with simultaneous measurements at low latitude, we address the question of the global character of the observed phenomena. The results show, for selected time intervals, the occurrence of simultaneous fluctuations at all the stations, with high coherence even between high and low latitude; it is interesting that these fluctuations are detected during open magnetospheric conditions, when the high latitude stations are situated well within the polar cap, i.e. far from closed field lines. http://hdl.handle.net/2122/2355 Titolo: A THERMODYNAMIC APPROACH TO THE MAGNETOSPHERIC COMPLEXITY: THE ROLE OF FLUCTUATIONS<br/><br/>Autori: Consolini, G.; 1Istituto di Fisica Spazio Interplanetario, INAF; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Kretzschmar, M.; Royal Observatory of Belgium, 1180 Brussels, Belgium<br/><br/>Abstract: Recent studies evidenced that the magnetotail dynamics looks like the one of an avalanchingsystem. This fact has been related with a near criticality dynamics and modelled by singular diffusionand transport equations. Here, we discuss some features of the Earth’s magnetotail dynamics usinga thermodynamic approach. In detailwediscuss the role played by fluctuations in singular diffusion andrelaxation processes from a non-equilibrium thermodynamics point of view. Moreover, the emergenceof non-Gaussian statistics is discussed in the framework of the thermodynamics of composite systems.