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  • 1
    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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  • 2
    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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  • 3
    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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  • 4
    Publication Date: 2024-01-08
    Description: 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.
    Description: Published
    Description: 9287
    Description: OSA3: Climatologia e meteorologia spaziale
    Description: JCR Journal
    Keywords: Turbulence ; Swarm constellation ; GPS Loss of Lock ; 01.02. Ionosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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