Physics
Scientific paper
May 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agusmsm33a..05c&link_type=abstract
American Geophysical Union, Spring Meeting 2007, abstract #SM33A-05
Physics
2439 Ionospheric Irregularities, 2487 Wave Propagation (0689, 3285, 4275, 4455, 6934), 2753 Numerical Modeling, 2768 Plasmasphere, 2772 Plasma Waves And Instabilities (2471)
Scientific paper
Studies of dispersions of lightning induced whistlers propagating along magnetic field lines and observed on the ground brought the first information about cold plasma environment of the Earth. Later, satellite measurements revealed new types of whistlers associated with oblique propagation that could not be observed on the Earth because of LHR reflection. Today, an investigation of whistler propagation and distribution of their energy in the inner magnetosphere draw attention owing to their influence on energetic electrons in radiation belts via wave- particle interaction. Modeling of whistler propagation is usually based on the following simplifying assumptions. A part of electromagnetic energy generated by lightning discharge leaks into the ionosphere and transforms into whistler wave mode. At the top of F2 layer, the wave field can be decomposed into many wave packets with wave vectors oriented vertically from the Earth's surface, which is justified by the increase of refractive index from bottom. The initial parameters of each wave packet are determined by its frequency and initial latitude. The wave number is calculated from the dispersion relation. Further, the propagation is supposed to be non-ducted (oblique) and a ray tracing calculation is performed to evaluate the arrival time of individual wave packets of specific frequency to a given location. In this work, we compare the real spectrograms observed by satellites (mainly MAGION-5) with results of the modeling. We show that for some observed whistlers we get very good agreement. However, we can also find many observations which we are able to model only partially or not at all. We discussed these observations. We suppose that to possible reasons of these disagreements count a multiple leakage of lightning energy from Earth-ionosphere wave guide at different rather distant locations, a combination of ducted and oblique propagation and wave scattering on small-scale irregularities.
Chum Jaroslav
Jiricek F.
Shklyar David R.
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