Kiel 2011 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 10: Poster: Astro- und geophysikalische Plasmen, warme dichte Plasmen

P 10.5: Poster

Dienstag, 29. März 2011, 17:00–19:00, Foyer

Modification of electromagnetic waves by upstreaming accoustic ones in the ionospheric E-layer before strong earthquakes — •Benjamin Mayer, Claudia-Veronika Meister, and Dieter Heinz Hermann Hoffmann — Institut für Kernphysik, TU Darmstadt, Schlossgartenstraße 9, 64289 Darmstadt, Germany

The many-fluid magnetohydrodynamic theory is applied to describe modifications and the additional excitation of electromagnetic waves in the ionospheric E-layer by acoustic waves originating from lower altitudes. In comparison to the works by other authors both the stratification of the ionosphere and the background electrostatic field are taken into account. The altitudinal profiles of the plasma parameters and the background electromagnetic field are fitted to recent experimental data. It is shown that normal magnetohydrodynamic waves, like Alfvén and magnetoacoustic ones, are generated in the E-layer. However, by the influence of the acoustic waves and the related modification of the momentum transport between the neutral and charged particles, the amplitudes and propagation directions of the magnetohydrodynamic waves are changed. Additional Joule heating processes caused by the acoustic waves and the forming nonlinear current systems result into temperature and plasma density modifications in the E-layer. Thus, also the characteristic f_0,E frequency changes, which is regularly measured by ionospheric sounding stations. Indeed, one day before 175 Asian earthquakes f_0,E modifications of, on the average, 30 % have been observed. The studied f_0,E variations seem not to be caused by the solar activity.