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  • 1
    Publication Date: 2020-11-19
    Description: 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.
    Description: ESA Contract No. 4000125663/18/I-NB (INTENS)
    Description: Published
    Description: e2019JA027429
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Keywords: field-aligned currents ; scaling properties ; 04.05. Geomagnetism ; 01.02. Ionosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2021-03-10
    Description: In the framework of space weather, the understanding of the physical mechanisms responsible for the generation of ionospheric irregularities is particularly relevant for their effects on global positioning and communication systems. Ionospheric equatorial plasma bubbles are one of the possible irregularities. In this work, using data from the ESA Swarm mission, we investigate the scaling features of electron density fluctuations characterizing equatorial plasma bubbles. Results strongly support a turbulence character of these structures and suggest the existence of a clear link between the observed scaling properties and the value of the Rate Of change of electron Density Index (RODI). This link is discussed, and RODI is proposed as a reliable proxy for the identification of plasma bubbles.
    Description: This research received 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: 759
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Keywords: Turbulence ; Electron density irregularities ; Equatorial topside ionosphere ; Swarm constellation ; 01.02. Ionosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2021-05-12
    Description: The present work focuses on the analysis of the scaling features of electron density fluctuations in the mid- and high-latitude topside ionosphere under different conditions of geomagnetic activity. The aim is to understand whether it is possible to identify a proxy that may provide information on the properties of electron density fluctuations and on the possible physical mechanisms at their origin, as for instance, turbulence phenomena. So, we selected about 4 years (April 2014–February 2018) of 1 Hz electron density measurements recorded on-board ESA Swarm A satellite. Using the Auroral Electrojet (AE) index, we identified two different geomagnetic conditions: quiet (AE 〈 50 nT) and active (AE 〉 300 nT). For both datasets, we evaluated the first- and second-order scaling exponents and an intermittency coefficient associated with the electron density fluctuations. Then, the joint probability distribution between each of these quantities and the rate of change of electron density index was also evaluated. We identified two families of plasma density fluctuations characterized by different mean values of both the scaling exponents and the considered ionospheric index, suggesting that different mechanisms (instabilities/turbulent processes) can be responsible for the observed scaling features. Furthermore, a clear different localization of the two families in the magnetic latitude— magnetic local time plane is found and its dependence on geomagnetic activity levels is analyzed. These results may well have a bearing about the capability of recognizing the turbulent character of irregularities using a typical ionospheric plasma irregularity index as a proxy
    Description: Published
    Description: 6183
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Keywords: Turbulence ; High-latitude ionosphere ; electron density fluctuations ; Swarm constellation ; 01.02. Ionosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
    Publication Date: 2021-05-12
    Description: We investigated the average polar patterns of ionospheric electron density and the corresponding patterns of scaling features as a function of interplanetary magnetic field orientation. The focus is on the Northern Hemisphere using electron density data recorded on-board ESA Swarm A satellite. The first- and second-order scaling exponents have been evaluated by means of the -order structure functions. We used electron density measurements over a period of 15 months from April 1, 2014 to June 30, 2015, which corresponds to the maximum of solar cycle 24 and which is characterized by an average value of the solar radio flux (F10.7) index equal to (140+/- 30) sfu. Electron density, first- and second-order scaling exponents have been mapped and discussed for four main IMF orientations provided by Bx and By components under conditions of high solar activity. Large spatial changes of the second-order scaling exponent pattern are observed with a steepening of the associated spectral exponent in correspondence with the nightside polar cap trailing edge. Intermittency, defined as the departure from linearity of the dependence of scaling exponents on moment order q, is also evaluated finding that it is generally higher near the equatorward boundary of the auroral oval than elsewhere. On the whole, the found patterns of the electron density first- and second-order scaling exponents suggest the occurrence of turbulence at the high latitudes.
    Description: Published
    Description: 105531
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Keywords: Polar ionosphere ; Turbulence ; Scaling feature ; Space weather ; Swarm satellite ; electron density ; 01.02. Ionosphere ; 01.03. Magnetosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
    Publication Date: 2020-04-14
    Description: The magnetosphere-ionosphere system is recognized as a complex and active element affected by space weather and as a region where important scientific questions related to space weather impacts need to be answered. In this framework, there is a high priority on the understanding of how local, regional, and global-scale phenomena couple to produce observed responses across various scales. Turbulence provides one pathway by which energy cascades across scales from large to small ones where energy can be dissipated in the form of heating. The Swarm mission, that is a true multi-point and multi-purpose constellation, represents a unique opportunity to address some of these scientific questions. In detail, it gives us a chance of investigating the nature and the scaling features of magnetic field fluctuations for different geomagnetic activity levels, and unveiling the role played by turbulence of ionospheric plasma medium on the magnetic field fluctuations. Recently, using Swarm magnetic field data at high-latitude in the Northern Hemisphere, the local scaling indices of the 1st and 2nd order structure functions of the magnetic field fluctuations have been evaluated, showing their capability both to give new insights about the ionosphere-magnetosphere coupling and to provide information on the ionospheric turbulence. Here, we improve and extend the analysis by investigating the scaling features of the geomagnetic field fluctuations of external origin, recorded by Swarm A satellite during a period of 2 years (April 2014–March 2016). Maps of the local Hurst exponent values, which allow us to study scaling properties of the geomagnetic field’s spatial fluctuations are shown, both at high-latitudes (in the Northern and Southern Hemisphere) and at low- and midlatitudes (±60°) according to two different geomagnetic activity conditions. The aim is to capture the essential features of the spatial fluctuations of the geomagnetic field and understand their origins.
    Description: Published
    Description: GM449
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Keywords: turbulence ; ionsophere ; geomagnetic field ; 01.02. Ionosphere ; 04.05. Geomagnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
    Publication Date: 2022-08-16
    Description: Ionospheric irregularities may affect electromagnetic signals propagating through the ionosphere and consequently contribute to the malfunctioning of the Global Navigation Satellite Systems hindering their accuracy and reliability. In this study, we use data recorded on board two of the three satellites of the Swarm constellation (namely, Swarm A and Swarm B) from July 15th, 2014 to December 31st, 2021 to assess the possible dependence of the Global Positioning System (GPS) signals loss of lock on the presence of a specific kind of ionospheric irregularities. To accomplish this task we study the scaling features of the electron density fluctuations through the structure function analysis simultaneously to the occurrence of loss of lock events through measurements recorded by the Langmuir probes and the precise orbit determination antennas on board Swarm A and Swarm B satellites. We find that the plasma density irregularities in a turbulent state characterized by intermittent structures and extremely high values of the Rate Of change of electron Density Index can lead to GPS loss of lock events. This is always true at mid- and high-latitudes, especially inside the auroral oval. In the equatorial belt, this happens in at least 75% of identified GPS loss of lock events that basically coincide with the occurrence of plasma bubbles.
    Description: Published
    Description: e2022SW003129
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Keywords: Turbulence ; ionosphere ; Loss of Lock events ; 01.02. Ionosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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