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  • 1
    Publication Date: 2012-06-28
    Description: Journal of the American Chemical Society DOI: 10.1021/ja209884h
    Print ISSN: 0002-7863
    Electronic ISSN: 1520-5126
    Topics: Chemistry and Pharmacology
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  • 2
    Publication Date: 2020-11-19
    Description: Some physical processes due to Sun-Earth interaction can influence the configuration and the dynamics of the high-latitude ionospheric plasma, particularly during geomagnetically disturbed periods. A possible consequence of this interaction is the occurrence of turbulent fluctuations that can be observed both in magnetic and electric fields and plasma density. Here, we focus on the intermittent nature of high-latitude ionospheric electron density fluctuations during geomagnetically disturbed periods as observed by one of the satellites of the ESA-Swarm constellation. The most obvious finding emerging from this study is the strong intermittent character of electron density fluctuations and the existence of an agreement between the anomalous scaling features of electron density fluctuations and those expected from a passive scalar quantity in fluid turbulence. This latter result supports the view of a passive scalar behavior of electron density in the high-latitude ionosphere that can have significant implications in the field of SpaceWeather studies.
    Description: financial support from European Space Agency (ESA contract N. 4000125663/18/I-NB-“EO Science for Society Permanently Open Call for Proposals EOEP-5 BLOCK4” (INTENS)) and from the Italian MIUR-PRIN grant 2017APKP7T on “Circumterrestrial Environment: Impact of Sun-Earth Interaction.”
    Description: Published
    Description: e2020GL089628
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Keywords: Electron density fluctuation ; High-latitude ionosphere ; Passive scalar ; Swarm constellation ; 01.02. Ionosphere ; 05.07. Space and Planetary sciences ; 01.03. Magnetosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2021-05-31
    Description: Field-aligned currents (FACs) flowing in the auroral ionosphere are a complex system of upward and downward currents, which play a fundamental role in the magnetosphere–ionosphere coupling and in the ionospheric heating. Here, using data from the ESA-Swarm multi-satellite mission, we studied the complex structure of FACs by investigating sign-singularity scaling features for two different conditions of a high-latitude substorm activity level as monitored by the AE index. The results clearly showed the sign-singular character of FACs supporting the complex and filamentary nature of these currents. Furthermore, we found evidence of the occurrence of a topological change of these current systems, which was accompanied by a change of the scaling features at spatial scales larger than 30 km. This change was interpreted in terms of a sort of symmetry-breaking phenomenon due to a dynamical topological transition of the FAC structure as a consequence of FACs and substorm current wedge intensification during substorms.
    Description: Italian PNRA under Contract PNRA18 00289-A “Space weather in Polar Ionosphere: the Role of Turbulence”.
    Description: Published
    Description: 708
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Keywords: Field-aligned currents ; Ionosphere ; fractals ; Complexty
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
    Publication Date: 2021-05-31
    Description: In the polar ionosphere, the electric field is characterized by broadband and power law spectral densities at small/short spatio-temporal scales, which support a possible turbulent nature of the electric field fluctuations. Here, we investigate the multifractal character of the full three-dimensional electric field in the polar ionosphere as recorded on board the first Chinese Seismo- Electromagnetic Satellite (CSES-01). The results of our analysis prove a clear different degree of multifractality of the electric field fluctuations approaching either the polar cap trailing edge or the auroral region. The observed differences in the multifractal character are interpreted in terms of the different natures of the particle precipitation in the polar cap and in the auroral region. A possible link between the multifractal nature of electric field fluctuations, parallel to the geomagnetic field, and filamentation of field aligned currents (FACs) is established
    Description: Contract ASI “LIMADOU Scienza+” n 2020-31-HH.0 PNRA18 00289-A “Space weather in Polar Ionosphere: the Role of Turbulence”.
    Description: Published
    Description: 646
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Keywords: auroral ionosphere ; electric field ; Turbulence ; Fractals ; 01.02. Ionosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
    Publication Date: 2020-07-23
    Description: Understanding the complex behavior of the near-Earth electromagnetic environment is one of the main challenges of Space Weather studies. This includes both the correct characterization of the different physical mechanisms responsible for its configuration and dynamics as well as the efforts which are needed for a correct forecasting of several phenomena. By using a nonlinear multi-scale dynamical systems approach, we provide here new insights into the scale-to-scale dynamical behavior of both quiet and disturbed periods of geomagnetic activity. The results show that a scale-dependent dynamical transition occurs when moving from short to long timescales, i.e., from fast to slow dynamical processes, the latter being characterized by a more regular behavior, while more dynamical anomalies are found in the behavior of the fast component. This suggests that different physical processes are typical for both dynamical regimes: the fast component, being characterized by a more chaotic and less predictable behavior, can be related to the internal dynamical state of the near-Earth electromagnetic environment, while the slow component seems to be less chaotic and associated with the directly driven processes related to the interplanetary medium variability. Moreover, a clear difference has been found between quiet and disturbed periods, the former being more complex than the latter. These findings support the view that, for a correct forecasting in the framework of Space Weather studies, more attention needs to be devoted to the identification of proxies describing the internal dynamical state of the near-Earth electromagnetic environment.
    Description: Published
    Description: 25
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Keywords: Earth's magnetospheric dynamics ; geomagnetic storms and substorms ; empirical mode decomposition ; geomagnetic indices ; 04.05. Geomagnetism ; 01.03. Magnetosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
    Publication Date: 2019-03-29
    Description: The Earth's magnetosphere is characterized by a complex dynamics resulting from the interaction of different multiscale processes which can be both directly driven/triggered by the interplanetary magnetic field and the solar wind, and due to internal processes of the magnetosphere. Recently, Alberti et al. (2017, https://doi.org/10.1002/2016JA023175) have shown that the fluctuations at distinct timescales of some geomagnetic indices differently respond to interplanetary changes during geomagnetic storms. In detail, using an information theory based approach it has been shown that geomagnetic indices fluctuations occurring at long timescales (typically longer than 200 min) are correlated with physical quantities characterizing the changes of the interplanetary conditions, while the short timescale ones (typically shorter than 200 min) do not seem to be directly related to the same physical quantities. The aim of this work is to identify the nature and character of the scale-to-scale fluctuations of two geomagnetic indices, AE and SYM-H, capable of monitoring different geomagnetic current systems related to the occurrence of geomagnetic storms and substorms. By applying the theory of dynamical systems, we investigate the scale-to-scale correlation dimension D2 and the Kolmogorov entropy K2 showing the occurrence of a topological phase transition phenomenon between long and short-timescale fluctuations. Furthermore, our results clearly show that the forecast horizon of fluctuations occurring at timescales shorter than 200 min dramatically decreases down to ∼2 min. The consequences of this result in the framework of Space Weather forecasting is briefly outlined and discussed.
    Description: Published
    Description: 9065–9077
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
    Publication Date: 2019-01-30
    Description: Abstract – The Earth’s magnetosphere responds to the external changes of interplanetary magnetic field and solar wind conditions showing a multiscale dynamics, manifesting in the occurrence of fluctuations over a very wide range of timescales. Here, using an approach based on a Langevin/Fokker-Planck description we investigate the nature of the fast (short-) and slow (long-timescale) fluctuations of SYM-H index during geomagnetic storms. The results point towards a different origin of the fast (s 〈 200 min) and slow (s 〉 200 min) fluctuations, which are characterized by state functions of different nature. In detail, the state function associated with the slow dynamics shows the evidence of the occurrence of first-order-like topological phase transition during the different phases of a geomagnetic storm, while the fast dynamics seems to be characterized by a quasi-invariant quadratic state function. A modeling in terms of stochastic Langevin equation is discussed and the relevance of our results in the framework of Space Weather studies is outlined.
    Description: Published
    Description: A56
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Keywords: Earth's magnetospheric dynamics ; geomagnetic storms and substorms ; geomagnetic indices ; space weather ; 01.03. Magnetosphere ; 04.05. Geomagnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
    Publication Date: 2020-02-06
    Description: Turbulence, intermittency, and self-organized structures in space plasmas can be investigated by using a multifractal formalism mostly based on the canonical structure function analysis with fixed constraints about stationarity, linearity, and scales. Here, the Empirical Mode Decomposition (EMD) method is firstly used to investigate timescale fluctuations of the solar wind magnetic field components; then, by exploiting the local properties of fluctuations, the structure function analysis is used to gain insights into the scaling properties of both inertial and kinetic/dissipative ranges. Results show that while the inertial range dynamics can be described in a multifractal framework, characterizing an unstable fixed point of the system, the kinetic/dissipative range dynamics is well described by using a monofractal approach, because it is a stable fixed point of the system, unless it has a higher degree of complexity and chaos.
    Description: Published
    Description: id 320
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Keywords: Solar wind ; scaling properties ; fractals ; chaos ; 05.07. Space and Planetary sciences
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 9
    Publication Date: 2022-04-22
    Description: An accurate understanding of dissimilarities in geomagnetic variability between quiet and disturbed periods has the potential to vastly improve space weather diagnosis. In this work, we exploit some recently developed methods of dynamical system theory to provide new insights and conceptual ideas in space weather science. In particular, we study the co-variation and recurrence statistics of two geomagnetic indices, SYM-H and AL, that measure the intensity of the globally symmetric component of the equatorial electrojet and that of the westward auroral electrojet, respectively. We find that the number of active degrees of freedom, required to describe the phase space dynamics of both indices, depends on the geomagnetic activity level. When the magnetospheric substorm activity, as monitored by the AL index, increases, the active number of degrees of freedom increases at high latitudes above the dimension obtained through classical time delay embedding methods. Conversely, a reduced number of degrees of freedom is observed during geomagnetic storms at low latitude by analysing the SYM-H index. By investigating time-dependent relations between both indices we find that a significant amount of information is shared between high and low latitude current systems originating from coupling mechanisms within the magnetosphere–ionosphere system as the result of a complex interplay between processes and phenomena of internal origin activated by the triggering of external source processes. Our observations support the idea that the near-Earth electromagnetic environment is a complex system far from an equilibrium
    Description: Published
    Description: 226
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Keywords: Space weather ; geomagnetic storms ; magnetospheric substorms ; geomagnetic indices ; 04.05. Geomagnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 10
    Publication Date: 2022-04-22
    Description: The recent Chinese Seismo-Electromagnetic Satellite (CSES-01) provides a good opportunity to investigate some features of plasma properties and its motion in the topside ionosphere. Using simultaneous measurements from the electric field detector and the magnetometers onboard CSES-01, we investigate some properties of the plasma ExB drift velocity for a case study during a crossing of the Southern auroral region in the topside ionosphere. In detail, we analyze the spectral and scaling features of the plasma drift velocity and provide evidence of the turbulent character of the ExB drift. Our results provide an evidence of the occurrence of 2D ExB intermittent convective turbulence for the plasma motion in the topside ionospheric F2 auroral region at scales from tens of meters to tens of kilometers. The intermittent character of the observed turbulence suggests that the macro-scale intermittent structure is isomorphic with a quasi-1D fractal structure, as happens, for example, in the case of a filamentary or thin-tube-like structure. Furthermore, in the analyzed range of scales we found that both magnetohydrodynamic and kinetic processes may affect the plasma dynamics at spatial scales below 2 km. The results are discussed and compared with previous results reported in the literature.
    Description: Published
    Description: 1936
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Keywords: Turbulence ; Auroral ionosphere ; ExB plasma motion ; 01.02. Ionosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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