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Berrilli, Francesco
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- PublicationOpen AccessDiffusion of emerging bipolar magnetic pairs in solar photosphereMagnetic element tracking has been widely used to study the transport and diffusion of the magnetic field on the solar photosphere. From the analysis of the displacement spectrum of these tracers, it has been recently agreed that a regime of super-diffusion dominates the solar surface. We present in this work the analysis of the diffusion of emerging new bipolar magnetic elements for different initial separation of the footpoints. The displacement spectrum for bipolar couples interestingly shows a similar behaviour with respect to the case where all magnetic pairs are considered. To understand how such peculiar diffusion in the solar atmosphere takes places, we compare the displacement spectrum exploring the initial maximum separation parameter.
126 35 - PublicationOpen AccessTesting the Steady-State Fluctuation Relation in the Solar Photospheric Convection(2020-06-28)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The turbulent thermal convection on the Sun is an example of an irreversible non-equilibrium phenomenon in a quasi-steady state characterized by a continuous entropy production rate. Here, the statistical features of a proxy of the local entropy production rate, in solar quiet regions at different timescales, are investigated and compared with the symmetry conjecture of the steady-state fluctuation theorem by Gallavotti and Cohen. Our results show that solar turbulent convection satisfies the symmetries predicted by the fluctuation relation of the Gallavotti and Cohen theorem at a local level.131 12 - PublicationRestrictedObservational evidence for buffeting-induced kink waves in solar magnetic elements(2014)
; ; ; ; ; ;Stangalini, M.; INAF - Osservatorio Astronomico di roma, Monte Porzio Catone, Italia ;Consolini, G.; INAF - Istituto di Astrofisica e Planetologia Spaziali, Roma, Italia ;Berrilli, F.; Università degli Studi di Roma Tor Vergata, Roma, Italia ;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; ;; ; The role of diffuse photospheric magnetic elements in the energy budget of the upper layers of the Sun’s atmosphere has been the recent subject of many studies. This was made possible by the availability of high temporal and spatial resolution observations of the solar photosphere, allowing large numbers of magnetic elements to be tracked to study their dynamics. In this work we exploit a long temporal series of seeing-free magnetograms of the solar photosphere to study the effect of the turbulent convection on the excitation of kink oscillations in magnetic elements. We make use of the empirical mode decomposition technique in order to study the transverse oscillations of several magnetic flux tubes. This technique permits analysis of non-stationary time series like those associated to the horizontal velocities of these flux tubes, which are continuously advected and dispersed by granular flows. Our primary findings reveal the excitation of low frequency modes of kink oscillations, which are subharmonics of a fundamental mode with a 7.6 ± 0.2 min periodicity. These results constitute observational proof of the excitation of kink waves by the buffeting of the convection cells in the solar photosphere, and they are discussed in light of their possible role in the energy budget of the upper Sun’s atmosphere.402 104 - PublicationOpen AccessThe ionosphere prediction service(2019)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ; ; ;The Ionosphere Prediction Service (IPS), project funded by European Commission within Horizon 2020 and currently ongoing, provides a prototype for a monitoring and prediction service of potential ionosphere-related disturbances affecting GNSS (Global Navigation Satellite System) user communities, to help these communities cope with the effects of the ionosphere and mitigate the related effects for the specific GNSS-based application/services. The aim of the IPS project is to design and develop a prototype platform able to translate the prediction and forecast of the ionosphere effects into a service customized for specific GNSS user communities. The objective is to alert the GNSS users in due time of an upcoming ionospheric event potentially harmful for GNSS and for the related operations in the given application field. The project team is composed of Telespazio (coordinator), Nottingham Scientific Ltd, Telespazio Vega DE, The University of Nottingham, The University of Rome Tor Vergata and the National Institute of Geophysics and Volcanology. The Joint Research Centre of the European Commission is also involved in the project.494 29 - PublicationOpen AccessStatistical behaviour of a proxy of the entropy production rate of the solar photosphereThe solar photosphere provides an incomparable laboratory to study turbulent convection in a dissipative non-equilibrium system. The evaluation of the entropy production rate on the solar photosphere and its probability distribution are the key issues for studying the non-equilibrium dynamics of the solar convection. The local entropy production rate is not offhandedly measurable on the solar photosphere, but it can be easily evaluated using the vertical heat flux as a proxy, which is given by the product between the line-of-sight velocity and the surface temperature. In this work, we present some preliminary results on statistics of the local entropy production rate via the vertical heat flux, using line-of-sight velocity and temperature maps of the solar photosphere which are derived from high-resolution spectro-polarimetric data making use of the Center of Gravity Method and the Stefan-Boltzmann law.
107 14 - PublicationOpen AccessScaling Properties of Magnetic Field Fluctuations in the High-Latitude IonosphereSpace plasma turbulence plays a relevant role in several plasma environments, such as solar wind and the Earth’s magnetosphere–ionosphere system, and is essential for describing their complex coupling. This interaction gives rise to various phenomena, including ionospheric irregularities and the amplification of magnetospheric and ionospheric currents. The structure and dynamics of these currents have relevant implications, for example, in studying ionospheric heating and the nature of electric and magnetic field fluctuations in the auroral and polar environments. In this study, we investigate the nature of small-scale fluctuations characterizing the ionospheric magnetic field in response to different geomagnetic conditions. We use high-resolution (50 Hz) magnetic data from the ESA’s Swarm mission, collected during a series of high-latitude crossings, to probe the scaling features of magnetic field fluctuations in auroral and polar cap regions at spatial scales still poorly explored. Our findings reveal that magnetic field fluctuations in field-aligned currents (FACs) and polar cap regions across both hemispheres are characterized by different scaling properties, suggesting a distinct driver of turbulence. Furthermore, we find that geomagnetic activity significantly influences the nature of energy dissipation in FAC regions, leading to more localized filamentary structures toward smaller scales.
42 10 - PublicationOpen AccessScaling properties of magnetic field fluctuations in the quiet SunContext. The study of the dynamic properties of small-scale magnetic fields in the quiet photosphere is important for several reasons: (i) it allows us to characterise the dynamic regime of the magnetic field and points out some aspects that play a key role in turbulent convection processes; (ii) it provides details of the processes and the spatial and temporal scales in the solar photosphere at which the magnetic fields emerge, vary, and eventually decay; and (iii) it provides physical constraints on models, improving their ability to reliably represent the physical processes occurring in the quiet Sun. Aims. We aim to characterise the dynamic properties of small-scale magnetic fields in the quiet Sun through the investigation of the scaling properties of magnetic field fluctuations. Methods. To this end, we applied the structure functions analysis, which is typically used in the study of complex systems (e.g. in approaching turbulence). In particular, we evaluated the so-called Hölder-Hurst exponent, which points out the persistent nature of magnetic field fluctuations in the field of view targeted at a whole supergranule in the disc centre. Results. We present the first map of a solar network quiet region as represented by the Hölder-Hurst exponent. The supergranular boundary is characterised by persistent magnetic field fluctuations, which indicate the occurrence of longer-memory processes. On the contrary, the regions inside the supergranule are characterised by antipersistent magnetic field fluctuations, which suggest the occurrence of physical processes with a short memory. Classical Kolmogorov homogeneous and isotropic turbulence, for instance, belongs to this class of processes. The obtained results are discussed in the context of the current literature.
300 40 - PublicationOpen AccessDecomposing solar and geomagnetic activity and seasonal dependencies to examine the relationship between GPS loss of lock and ionospheric turbulence(2023-06-07)
; ; ; ; ; ; ; ; ; ; ; Ionospheric irregularities are plasma density variations that occur at various altitudes and latitudes and whose size ranges from a few meters to a few hundred kilometers. They can have a negative impact on the Global Navigation Satellite Systems (GNSS), on their positioning accuracy and even cause a signal loss of lock (LoL), a phenomenon for which GNSS receivers can no longer track the satellites' signal. Nowadays, the study of plasma density irregularities is important because many of the crucial infrastructures of our society rely on the efficient operation of these positioning systems. It was recently discovered that, of all possible ionospheric plasma density fluctuations, those in a turbulent state and characterized by extremely high values of the Rate Of change of the electron Density Index appear to be associated with the occurrence of LoL events. The spatial distributions of this class of fluctuations at mid and high latitudes are reconstructed for the first time using data collected on Swarm satellites between July 15th, 2014 and December 31st, 2021, emphasizing their dependence on solar activity, geomagnetic conditions, and season. The results unequivocally show that the identified class of plasma fluctuations exhibits spatio-temporal behaviours similar to those of LoL events.141 7 - PublicationOpen AccessOccurrence and persistence of magnetic elements in the quiet SunTurbulent convection efficiently transports energy up to the solar photosphere, but its multi-scale nature and dynamic properties are still not fully understood. Several works in the literature have investigated the emergence of patterns of convective and magnetic nature in the quiet Sun at spatial and temporal scales from granular to global. Aims. To shed light on the scales of organisation at which turbulent convection operates, and its relationship with the magnetic flux therein, we studied characteristic spatial and temporal scales of magnetic features in the quiet Sun. Methods. Thanks to an unprecedented data set entirely enclosing a supergranule, occurrence and persistence analysis of magnetogram time series were used to detect spatial and long-lived temporal correlations in the quiet Sun and to investigate their nature. Results. A relation between occurrence and persistence representative for the quiet Sun was found. In particular, highly recurrent and persistent patterns were detected especially in the boundary of the supergranular cell. These are due to moving magnetic elements undergoing motion that behaves like a random walk together with longer decorrelations ($\sim2$ h) with respect to regions inside the supergranule. In the vertices of the supegranular cell the maximum observed occurrence is not associated with the maximum persistence, suggesting that there are different dynamic regimes affecting the magnetic elements.
148 121 - PublicationRestrictedThe Ionosphere Prediction Service(2018)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ;The aim of the Ionosphere Prediction Service (IPS) project is to design and develop a prototype platform to translate the prediction and forecast of the ionosphere effects into a service customized for specific GNSS user communities. The project team is composed by Telespazio (coordinator), Nottingham Scientific Ltd, Telespazio Vega Deutschland, the University of Nottingham, the University of Rome “Tor Vergata” and the Italian Istituto Nazionale di Geofisica e Vulcanologia (INGV). The IPS development is conceived of two concurrent activities: prototype service design and development & research activity that will run along the whole project. Service design and development is conceived into four phases: user requirements collection, architecture specification, implementation and validation of the prototype. A sub-activity analyses also the integration feasibility in the Galileo Service center, located in Madrid. The research activity is the scientific backbone of IPS that will provide the models and algorithms for the forecasting products.111 2