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  • 2020-2024  (2)
  • 2020-2023  (3)
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  • 1
    Publication Date: 2021-10-20
    Description: The global statistical median behavior of the electron temperature (Te) in the topside ionosphere was investigated through in-situ data collected by Langmuir Probes on-board the European Space Agency Swarm satellites constellation from the beginning of 2014 to the end of 2020. This is the first time that such an analysis, based on such a large time window, has been carried out globally, encompassing more than half a solar cycle, from the activity peak of 2014 to the minimum of 2020. The results show that Swarm data can help in understanding the main features of Te in the topside ionosphere in a way never achieved before. Te data measured by Swarm satellites were also compared to data modeled by the empirical climatological International Reference Ionosphere (IRI) model and data measured by Jicamarca (12.0 S, 76.8 W), Arecibo (18.2 N, 66.4 W), and Millstone Hill (42.6 N, 71.5 W) Incoherent Scatter Radars (ISRs). Moreover, the correction of Swarm Te data recently proposed by Lomidze was applied and evaluated. These analyses were performed for two main reasons: (1) to understand how the IRI model deviates from the measurements; and (2) to test the reliability of the Swarm dataset as a new possible dataset to be included in the underlying empirical dataset layer of the IRI model. The results show that the application of the Lomidze correction improved the agreement with ISR data above all at mid latitudes and during daytime, and it was effective in reducing the mismatch between Swarm and IRI Te values. This suggests that future developments of the IRI Te model should include the Swarm dataset with the Lomidze correction. However, the existence of a quasi-linear relation between measured and modeled Te values was well verified only below about 2200 K, while for higher values it was completely lost. This is an important result that IRI Te model developers should properly consider when using the Swarm dataset.
    Description: Published
    Description: 4077
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2022-02-02
    Description: Ion temperature data recorded by Millstone Hill incoherent scatter radar (42.61 N, 288.51 E) over four full solar cycles (from 1970 to 2018) are analyzed to depict its climatological behavior in the range of altitudes between 100 and 550 km. The ion temperature dependencies on altitude, local time, month of the year, and solar activity level are studied through a climatological analysis based on binning and boxplot representation of statistical values. Binned observations of ion temperature are compared with International Reference Ionosphere (IRI) modeled values (IRI-2016 version). This comparison reveals several shortcomings in the IRI modeling of the ion temperature at ionosphere altitudes, in particular for the altitudinal, diurnal, seasonal, and solar activity description. The main finding of this study is that the overall IRI overestimation of the ion temperature can be probably ascribed to the long-term ionosphere cooling. Moreover, the study suggests that the IRI ion temperature model needs to implement the seasonal and solar activity dependence, and introduce a more refined diurnal description to allow multiple diurnal maxima seen in observations. The IRI ion temperature anchor point at 430 km is investigated in more detail to show how also a better description of the altitude dependence is desirable for modeling purposes. Some hints and clues are finally given to improve the IRI ion temperature model.
    Description: Published
    Description: 2186-2203
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2022-10-13
    Description: This paper is a review of the International Reference Ionosphere (IRI) project and model. IRI is recognized as the official standard for the Earth's ionosphere by the International Standardization Organization, the International Union of Radio Science, the Committee on Space Research, and the European Cooperation for Space Standardization. As requested by these organizations, IRI is an empirical (data-based) model representing the primary ionospheric parameters based on the long data record that exists from ground and space observations of the ionosphere. The core model describes monthly averages of the electron density, electron temperature, ion temperature, and ion composition globally in the altitude range from 60 to 2,000 km. Over time additional parameters were added in response to requests from the user community, this includes the equatorial ion drift, the occurrence probability of spread-F and of an F1 layer, auroral boundaries and the electron content from the bottom of the ionosphere to user-specified altitude. IRI has undergone extensive validations and is used for a wide range of applications in science, engineering, and education. This review is the result of many requests we have received for a comprehensive description of the model. It is also meant as a guide for users who are interested in a deeper understanding of the model architecture and its mathematical formalism.
    Description: Published
    Description: e2022RG000792
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
    Publication Date: 2024-03-19
    Description: Electron density (Ne) and electron temperature (Te) observations collected by Langmuir Probes on board the European Space Agency (ESA) Swarm B satellite are used to characterize their correlation in the topside ionosphere at an altitude of about 500 km. Spearman correlation coefficient values (RSpearman) are calculated on joint probability distributions between Ne and Te for selected conditions. The large data set of Swarm B observations at 2-Hz rate, covering the years 2014–2022, allowed investigating the correlation properties of the topside ionospheric plasma on a global scale, for different diurnal and seasonal conditions, with both a coverage and a detail never reached before. Results are given as maps of RSpearman as a function of the Quasi-Dipole (QD) magnetic latitude and magnetic local time (MLT) coordinates. The characterization of the correlation at high latitudes, along with the description of the diurnal trend at all latitudes, are the new findings of this study. The main correlation features point out a negative correlation at the morning overshoot, during daytime at mid latitudes, and during nighttime at the ionospheric trough and subauroral latitudes. Conversely, a positive correlation dominates the nighttime hours at mid and low latitudes and, to a minor extent, the low latitudes from 09 MLT onwards. A seasonal dependence of the correlation is noticeable only at very high latitudes where the general pattern of the negative correlation does not hold around ±75° QD latitude in the summer season. Results from Swarm B have been statistically compared and discussed with observations from the Arecibo, Jicamarca, and Millstone Hill incoherent scatter radars.
    Description: Published
    Description: e2023JA032201
    Description: OSA3: Climatologia e meteorologia spaziale
    Description: JCR Journal
    Keywords: ionosphere ; 01.02. Ionosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
    Publication Date: 2024-04-17
    Description: This study focuses on the open question of the electron temperature (Te) variation with solar activity in the topside ionosphere at mid- and high latitudes. It takes advantage of in situ observations taken over a decade (2014–2023) from Langmuir probes on board the low-Earth-orbit Swarm B satellite and spanning an altitude range of 500–530 km. The study also includes a comparison with Te values modeled using the International Reference Ionosphere (IRI) model and with Millstone Hill (42.6° N. 71.5° W) incoherent scatter radar observations. The largest Te variation with solar activity was found at high latitudes in the winter season, where Te shows a marked decreasing trend with solar activity in the polar cusp and auroral regions and, more importantly, at sub-auroral latitudes in the nightside sector. Differently, in the summer season, Te increases with solar activity in the polar cusp and auroral regions, while for equinoxes, variations are smaller and less clear. Mid-latitudes generally show negligible Te variations with solar activity, which are mostly within the natural dispersion of Te observations. The comparison between measured and modeled values highlighted that future implementations of the IRI model would benefit from an improved description of the Te dependence on solar activity, especially at high latitudes.
    Description: Published
    Description: 490
    Description: OSA3: Climatologia e meteorologia spaziale
    Description: JCR Journal
    Keywords: 01.02. Ionosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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