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Turbulence characteristics inside ionospheric small-scale expanding structures observed with SuperDARN HF radars

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Author(s): R. André | C. Hanuise | J.-P. Villain | V. Krasnoselskikh

Journal: Annales Geophysicae
ISSN 0992-7689

Volume: 21;
Issue: 8;
Start page: 1839;
Date: 0000;
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ABSTRACT
Unusual structures characterized by a very high-velocity divergence have been observed in the high-latitude F-region with SuperDARN radars (André et al., 2000). These structures have been interpreted as due to local demagnetization of the plasma in the ionospheric F-region, during very specific geophysical conditions. In this study, the collective wave scattering theory is used to characterize the decameter-scale turbulence (l approx 15 m) inside the structures. The distribution function of the diffusion coefficient is modified when the structures are generated, suggesting that two regimes of turbulence coexist. A temporal analysis decorrelates the two regimes and gives access to the dynamics associated with the structures. It is shown that a high turbulent regime precedes the plasma demagnetization and should be related to an energy deposition. Then a second regime appears when the plasma is demagnetized and disappears simultaneously with the structures. This study is the first application of the collective wave scattering theory to a specific geophysical event.Key words. Ionosphere (auroral ionosphere; ionospheric irregularities) – Space plasma physics (turbulence)

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