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The spatial and temporal dynamics of ionospheric currents are among the most evident manifestations of the interaction between the magnetized plasma of solar origin and the magnetosphereionosphere system. In this context, a special role is played by field-aligned currents (FACs), which drive energy and momentum exchanges between the magnetosphere and the ionosphere, deeply affecting the energy balance of the latter. One of the most relevant physical quantities that may help to fully characterize FACs is the ionospheric electrical conductivity. Understanding the features associated with this quantity may contribute to the advancement of knowledge on the mechanisms of solar windmagnetosphere-ionosphere interaction as well as energy storage and dissipation involved in the space weather phenomena. By extending a previous study, we investigate the dependence of the electrical conductivity parallel to the geomagnetic field on solar and geomagnetic activity. To this aim, we considered a six-year long data set of in-situ electron density and temperature values recorded by the Langmuir probes on board the Swarm satellites in the topside ionosphere. With this large data set, we computed global maps of the parallel electron conductivity under both quiet and disturbed conditions, and for different solar activity levels. In both cases, the International Reference Ionosphere (IRI) model allowed estimating the contribution of particle precipitation to electrical conductivity. [ABSTRACT FROM AUTHOR]

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 Space Weather studies. Plain Language Summary: Turbulence phenomena represent a key element for understanding the ionospheric dynamics and have a great impact on the features of both magnetic and electric fields and plasma density. It has been suggested that turbulence can be one of the mechanisms responsible for the generation of ionospheric irregularities, which may strongly affect the satellite navigation, positioning, and communication systems. In such a framework the characterization of turbulent fluctuations of ionospheric plasma parameters paves the way for a better modeling of space weather related phenomena. The ESA‐Swarm mission provides a unique opportunity to investigate the relevance of turbulence phenomena in the topside ionosphere. Using data recorded on board Swarm A satellite at high latitudes, the intermittent and passive scalar features of electron density fluctuations are investigated. The obtained results support the idea that plasma density irregularities exhibit a complex dynamic behavior similar to that of a turbulent field. Turbulence is therefore confirmed as a fundamental element to be taken into account in order to fully understand the occurrence of large local electron density gradients. Key Points: The ionospheric electron density fluctuations show an intermittent and passive scalar behaviorPlasma irregularities exhibit a complex dynamic behavior similar to a turbulent velocity fieldTurbulence is a key point to understand the occurrence of large local electron density gradients [ABSTRACT FROM AUTHOR]

The scaling features of electron density fluctuations during the St. Patrick's magnetic storm (17 March 2015) are analyzed to try to characterize the possible turbulent nature of the ionosphere during the development of the geomagnetic storm. The electron density values recorded by two of the three satellites of Swarm constellation during a period of 7 days (16–22 March 2015) around the storm peak are analyzed at middle‐ and high‐latitude regions in both hemispheres. The analysis reveals interesting patterns in the scaling properties of electron density fluctuations and a possible explanation for the occurrence of high values of the Rate of change Of the electron Density Index (RODI). Indeed, the obtained results seem to suggest that very high values of RODI, which describes the structuring of the plasma within a fixed time and is used as an ionospheric disturbance index, are correlated with the antipersistent character of electron density fluctuations and with the values around 5/3 of the power spectral density scaling exponent. These features are independent of the different phases of the analyzed geomagnetic storm and seem to support the idea of a fluid and/or magnetohydrodynamic turbulence as the main responsible of the high values of RODI recorded at high latitudes in the auroral and polar cap regions. Plain Language Summary: Electron density fluctuations characterizing the ionospheric plasma during the St. Patrick's geomagnetic storm occurred on 17 March 2015 are analyzed to investigate their possible turbulent nature. To perform this study, electron density values recorded by two of the three satellites of the Swarm constellation are considered at middle and high latitudes of both hemispheres between 16 and 22 March 2015. Results show that electron density fluctuations present interesting patterns and that high values of the Rate Of change of electron Density Index (RODI), which is used as an ionospheric disturbance index, may be related to a turbulent dynamics of the ionosphere. Specifically, independently of the different phases of the analyzed geomagnetic storm, the observed features seem to support the idea of a fluid and/or magnetohydrodynamic turbulence as the main cause of the high values of RODI recorded at high latitudes in the auroral and polar cap regions. Key Points: Self‐similarity/affinity nature of the plasma density fluctuations in the F region of middle‐ and high‐latitude ionospherePlasma density fluctuations at high latitudes in the auroral and polar cap regions seem to be related to a turbulent ionospheric dynamicsHigh values of RODI can be a proxy of the occurrence of ionospheric turbulence [ABSTRACT FROM AUTHOR]

Recent findings on the nature of magnetic field fluctuations in the high‐latitude ionospheric regions have suggested the existence of scaling features, which are the signature of the occurrence of turbulence. These features mainly characterize the magnetic field fluctuations in those regions where the field‐aligned currents flow. Here, we investigate the nature of the Earth's magnetic field fluctuations using the high‐resolution (50 Hz) magnetic measurements from the European Space Agency Earth's observation mission Swarm. Our study indicates that spatiotemporal anomalous scaling features characterize low‐frequency magnetic field fluctuations in the high‐latitude ionospheric regions of field‐aligned currents at spatial scales in the range 0.8–80 km (timescales in the range 0.1–10 s). The signature of a multifractal nature of these fluctuations suggests a highly complex structure of the field‐aligned currents. Our results support the view of inhomogeneous (filamentary) field‐aligned currents, which can have relevant implications in the comprehension of the physical processes responsible for the magnetospheric‐ionospheric coupling and ionospheric heating. Key Points: Low‐frequency magnetic field fluctuations in the topside F region polar ionosphere show scale‐invarianceAnomalous scaling (multifractal/intermittent) features and anisotropy of magnetic field fluctuations are studiedA link between the scale‐invariance of fluctuations and the filamentary nature of field‐aligned currents is discussed [ABSTRACT FROM AUTHOR]

Some features, such as vortex structures often observed through a wide spread of spatial scales, suggest that ionospheric convection is turbulent and complex in nature. Here, applying concepts from information theory and complex system physics, we firstly evaluate a pseudo Shannon entropy, H, associated with the polar cap potential obtained from the Super Dual Auroral Radar Network (SuperDARN) and, then, estimate the degree of disorder and the degree of complexity of ionospheric convection under different Interplanetary Magnetic Field (IMF) conditions. The aforementioned quantities are computed starting from time series of the coefficients of the 4th order spherical harmonics expansion of the polar cap potential for three periods, characterised by: (i) steady IMF Bz > 0, (ii) steady IMF Bz < 0 and (iii) a double rotation from negative to positive and then positive to negative Bz. A neat dynamical topological transition is observed when the IMF Bz turns from negative to positive and vice versa, pointing toward the possible occurrence of an order/disorder phase transition, which is the counterpart of the large scale convection rearrangement and of the increase of the global coherence. This result has been confirmed by applying the same analysis to a larger data base of about twenty days of SuperDARN data, allowing to investigate the role of IMF By too. [ABSTRACT FROM AUTHOR]

The ionospheric and magnetospheric current systems are responsible of the daily magnetic field changes. Recently, the Natural Orthogonal Components (NOC) technique has been applied to model the physical system responsible of the daily variation of the geomagnetic field, efficiently and accurately (Xu and Kamide, 2004). Indeed, this approach guarantees that the number of parameters used to represent the physical process is small as much as possible, and consequently process control for such system becomes apparent. We focus our present study on the analysis of the hourly means of the magnetic elements H, D and Z recorded at L'Aquila observatory in Italy from 1993 to 2004. We apply to this dataset the NOC technique to reconstruct the 3- dimensional structures of the different ionospheric and magnetospheric current systems which contribute to the geomagnetic daily variations. To support our interpretation in terms of the different ionospheric and magnetospheric current systems, the spectral and statistical features of the time dependent amplitudes associated to the set of natural orthogonal components are analyzed and compared to those of a set of descriptors of the magnetospheric dynamics and solar wind changes. [ABSTRACT FROM AUTHOR]