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Scale dependence and frontal formation of nighttime medium‐scale traveling ionospheric disturbances
Author(s) -
Yokoyama Tatsuhiro
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/grl.50905
Subject(s) - ionosphere , wavelength , physics , wavefront , instability , middle latitudes , perturbation (astronomy) , polarization (electrochemistry) , geophysics , scale (ratio) , computational physics , atmospheric sciences , optics , mechanics , astronomy , quantum mechanics , chemistry
Scale dependence of nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) is studied with the midlatitude ionosphere electrodynamics coupling model by changing initial perturbation scales. It is shown that both sporadic E ( E s ) layer and Perkins instabilities have the scale dependence that a shorter wavelength mode tends to stop growing within a shorter period, whereas a very long wavelength mode grows so slowly in the E region that it does not effectively seed the Perkins instability in the F region. As a result, the typical wavelength of MSTIDs (100–200 km) can be spontaneously generated without scale‐dependent forcing. It is also shown that long frontal structures of MSTIDs can be formed by the Pedersen polarization process along the wavefront of MSTIDs by which the wavefront is forced to be uniformly distributed.