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Traitement et analyse de données de systèmes radar HF : Etude des perturbations ionosphériques détectées à l'équateur magnétique avec le radar LDG et à moyenne latitude avec le réseau de Francourville

Abstract : The thesis shows a study of ionospheric perturbations measured at low and mid latitude. Two HF measurement devices are used. This leads to have two distinct parts.
The first part shows the analysis of the data recorded by the HF radar of the LDG in 1993 at the magnetic equator. Observations show the presence of radar echoes quite complex which are difficult to identify their origin. A very detailed analysis of the parameters (radar characteristics, propagation effect versus the radar frequency, and the mechanisms of irregularity generation in the equatorial ionosphere) is done. A numerical simulation allows the understanding of the echoes reflected or scattered by the equatorial ionosphere irregularities. A second study documents for the first time the development of irregularities in the equatorial F region during daytime.
The second part of the thesis details the effects of two different sources (solar eclipse and large earthquakes) measured by the HF network of Francourville.
The solar eclipse of August 11, 1999, modified the electron source term during three hours. With ionograms and Doppler sounding, the coefficients of different loss processes and the transport speed of the electrons and ions have been calculated. The atmospheric gravity wave, generated by the supersonic motion of the shadow of the Moon on the Earth, has been clearly identified in ionospheric measurements and in additional infrasound measurements. Two sources are distinguished: in the stratosphere for the ground-based measurements and a local source for the ionospheric measurements. Lastly, cartography of the temporal change of the perturbation induced by the eclipse over Western Europe at 180 km height is done with the use of 11 other ionosondes.
From August to November 1999, the effects of height earthquakes, with a surface magnitude higher than 6, have been measured in the ionosphere. The seismograms are compared to the Doppler measurements. The thermospheric filter effect is deduced from the Doppler data.
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Contributor : Thomas Farges <>
Submitted on : Tuesday, September 26, 2006 - 1:18:25 PM
Last modification on : Wednesday, November 29, 2017 - 3:02:23 PM
Long-term archiving on: : Tuesday, April 6, 2010 - 1:13:11 AM

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Thomas Farges. Traitement et analyse de données de systèmes radar HF : Etude des perturbations ionosphériques détectées à l'équateur magnétique avec le radar LDG et à moyenne latitude avec le réseau de Francourville. Astrophysique [astro-ph]. Université Paris Sud - Paris XI, 2000. Français. ⟨tel-00100361⟩

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