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  • 01.02. Ionosphere  (2)
  • In-situ electron density observations  (1)
  • 1
    Publication Date: 2024-01-29
    Description: The ionospheric equivalent slab thickness (𝜏), defined as the ratio of the vertical total electron content (vTEC) to the ionospheric F2‑layer electron density maximum (NmF2), is a parameter providing useful information on the shape of the vertical electron density profile. However, the use of this information is of difficult practical application in empirical ionosphere models, such as the NeQuick, because by design they do not explicitly include 𝜏 as a modelling parameter. In this work, we investigated the opportunity of using measured 𝜏 values to improve the empirical modelling of the ionosphere vertical electron density profile by NeQuick. Measured 𝜏 values were obtained through NmF2 observations and vTEC measurements obtained between 2001 and 2019 by an ionosonde and a ground-based GNSS receiver, respectively, co‑located at Rome ionospheric station (41.8° N, 12.5° E; Italy). NeQuick 𝜏 was obtained as the ratio between modelled NmF2 and vTEC values, the latter calculated by integration of the vertical profile. As a first step, 𝜏 values modelled by NeQuick were compared with corresponding values measured at Rome station to highlight diurnal, seasonal, and solar activity differences. Then, measured 𝜏 values were ingested in NeQuick through a three-parameter assimilation procedure which first assimilates F2‑layer peak characteristics to constrain the F2‑layer anchor point, and then assimilates vTEC to optimize the F2‑layer shape through the NeQuick F2‑layer thickness parameter, namely B2bot. The assimilation procedure provides information on how the NeQuick B2bot has to be modified to match measured 𝜏 values, and then on how the shape of the F2‑layer profile has to be changed accordingly. Our results highlight that, in many cases, the NeQuick B2bot has to be increased to match observations, which has implications on the modelling of the NeQuick bottomside and topside effective scale heights.
    Description: Published
    Description: PA528
    Description: OSA3: Climatologia e meteorologia spaziale
    Description: JCR Journal
    Keywords: Ionospheric equivalent slab thickness ; NeQuick model ; Ionosphere modelling ; Data assimilation ; Effective scale height ; 01.02. Ionosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2024-06-13
    Description: The topside ionosphere extends from the F2-layer peak, where the electron density reaches its absolute maximum in the ionosphere, to the overlying plasmasphere and magnetosphere. In the topside ionosphere, the electron density decreases with height with a vertical variation rate strongly dependent on height itself. The last version of the International Reference Ionosphere (IRI) model, i.e., IRI-2020, describes this complex behavior through four topside options based on different sub-models (i.e., options) developed from the 1970s to the present. All these options have in common the F2-layer peak as an anchor point, while they differ in their topside electron density profile and/or plasma effective scale height formulations. In this work, we perform a validation of the accuracy of the four IRI-2020 topside options based on the comparison against in-situ electron density observations by Gravity Recovery and Climate Experiment (GRACE), Ionospheric Connection Explorer (ICON), and Defense Meteorological Satellite Program (DMSP) F15 low-Earth-orbit satellites. Datasets used in this study encompass observations recorded from 1999 to 2022, covering different diurnal, seasonal, and solar activity conditions, on a global basis and for the height range 400–850 km above the ground. The nearly two solar cycles dataset facilitated the evaluation of IRI-2020 topside options ability to reproduce the spatial and time variations of the topside ionosphere for different solar activity conditions. The weaknesses and strengths of each IRI-2020 topside option are highlighted and discussed, and suggestions on how to improve the modeling of the challenging topside ionosphere region within the IRI model are provided for future reference.
    Description: In press
    Description: OSA3: Climatologia e meteorologia spaziale
    Description: JCR Journal
    Keywords: Topside ionosphere modeling ; International Reference Ionosphere (IRI) model ; In-situ electron density observations ; Low-Earth-Orbit satellites ; 01.02. Ionosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
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