Characteristics of high-latitude TIDs from different causative mechanisms deduced by theoretical modeling

Details Characteristics of high-latitude TIDs from different causative mechanisms deduced by theoretical modeling Characteristics of high-latitude TIDs from different causative mechanisms deduced by theoretical modeling

Mar 1997

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997jgr...102.4597k&link_type=abstract

Journal of Geophysical Research, Volume 102, Issue A3, p. 4597-4612

Other

6

Ionosphere: Auroral Ionosphere, Ionosphere: Ionospheric Disturbances, Ionosphere: Modeling And Forecasting, Ionosphere: Wave Propagation

Scientific paper

The high-latitude ionosphere is a physically complex regime where traveling ionospheric disturbance signatures (TIDs) are caused not only by atmospheric gravity waves (AGWs) but also by other processes. Among these, wavelike variations in E×B drift strength, particle precipitation intensity, and ionospheric return current density are the most relevant ones; they can produce TIDs similar to AGW/TIDs (typical periods around 1 hour), frequently seen, for example, in incoherent scatter (IS) data. This study is concerned with elucidating the characteristics of TIDs from these different mechanisms in the high-latitude F region, aiming at three major aspects: (1) the causative mechanism-TID relationship, (2) the interpretation of TIDs in ionospheric data, especially IS data, in terms of causative mechanisms, and (3) the reliable recognition of AGW-induced TIDs, which are of special interest. To study these aspects tailored to IS data exploitation, theoretical simulations of TIDs were performed for representative cases of the causative mechanisms, utilizing a realistic ionospheric model (``Graz Ionospheric Flux Tube Simulation (GIFTS) model'') which self-consistently yields the fundamental TID quantities, electron density, ion drift, ion and electron temperature, and further mechanism-dependent quantities. The physical understanding of the non-AGW/TIDs could be significantly improved. A general finding was that because of nonlinear processes (e.g., frictional heating) and its coupling to the thermosphere, the ionosphere is capable of generating complicated TID waveforms (e.g., a dominant second harmonic) even for a monochromatic source mechanism. TID information derivable from IS data was found sufficiently unique for each mechanism to allow its identification. In particular, the unique features of AGW/TIDs allow their reliable recognition among other TIDs. The results provide a good basis for future automation of the recognition and quantification of causative mechanisms based on IS data.

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