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  • 01.02. Ionosphere  (2)
  • Frontiers  (1)
  • Springer  (1)
  • Blackwell Publishing Ltd
  • 2020-2022  (2)
  • 1
    Publication Date: 2021-01-29
    Description: The abnormal electromagnetic emissions recorded by DEMETER (the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite associated with the April 6, 2010 Mw 7.8 northern Sumatra earthquake are examined in this study. The variations of wave intensities recorded through revisiting orbits from August 2009 to May 2010 indicate that some abnormal enhancements at Extremely Low Frequency range of 300–800 Hz occurred from 10 to 3 days before the main shock, while they remained a relatively smooth trend during the quiet seismic activity times. The perturbation amplitudes relative to the background map which were built by using the same-time seasonal window (February 1 to April 30) data from 2008 to 2010 further suggest strong enhancements of wave intensities during the period prior to the earthquake. We further computed the wave propagation parameters for the electromagnetic field waveform data by using the Singular Value Decomposition method, and results show that there are certain portions of the Extremely Low Frequency emissions obliquely propagating upward from the Earth toward outer space direction at 10 and 6 days before the main shock. The potential energy variation of acoustic-gravity wave suggests the possible existence of acousticgravity wave stability with wavelengths roughly varying from 5.5 to 9.5 km in the atmosphere at the time of the main shock. In this study, we comprehensively investigated the link between the electromagnetic emissions and the earthquake activity through a convincing observational analysis, and preliminarily explored the seismic-ionospheric disturbance coupling mechanism, which is still not fully understood at present by the scientific community.
    Description: Published
    Description: 572393
    Description: 7T. Variazioni delle caratteristiche crostali e precursori sismici
    Description: JCR Journal
    Keywords: earthquake precursors ; ionospheric precursors ; 01.02. Ionosphere ; 04.05. Geomagnetism ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2020-09-01
    Description: This paper is a final review of the Simplified Ionospheric Regional Model (SIRM) devel- oped as a prototype in the early 1990s and improved in the following years. By means of an algorithm based on the Fourier synthesis, the SIRM model in its prototype version pro- vides predicted monthly median values of the main ionospheric characteristics such as: the ordinary wave critical frequencies (foE, foF1, and foF2) of the E, F1, and F2 ionospheric layers; the lowest virtual height (h’F) of the ordinary trace of the F region; the obliquity factor for a distance of 3000 km (M(3000)F2). Instead, the improved version focuses only on foF2 and M(3000)F2. The SIRM model has been largely employed in the framework of different international research projects as the climatological reference to output foF2 and M(3000)F2 monthly median predictions, but in its SIRMUP version is used also as a nowcasting model and as an intermediate step of complex procedures for a near real- time three-dimensional representation of the ionospheric electron density. In this regard, some results provided by both SIRM and SIRMUP for telecommunication applications are shown. Moreover, the mathematical treatment concerning both the phase correction of the Fourier synthesis and the fundamental steps carried out to define the SIRM algorithm in its final version, never published so far, will be described in detail in dedicated Appendices. Finally, for the first time the SIRM code is now downloadable for the benefit of users.
    Description: Published
    Description: 1143-1178
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Keywords: SIRM ; SIRMUP ; foF2 ; M(3000)F2 ; Regional modelling ; 01.02. Ionosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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