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The comparative importance of DE 3, SE 2, and SPW 4 on the generation of wavenumber‐4 longitude structures in the low‐latitude ionosphere during September equinox
Author(s) -
Pedatella N. M.,
Hagan M. E.,
Maute A.
Publication year - 2012
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 - 10.1029/2012gl053643
Subject(s) - longitude , ionosphere , wavenumber , latitude , daytime , geology , atmospheric sciences , zonal and meridional , variation (astronomy) , geophysics , geodesy , physics , astrophysics , optics
Numerical simulations are performed to investigate the generation of the wave‐4 longitude variation in the low‐latitude ionosphere due to the diurnal eastward propagating nonmigrating tide with zonal wavenumber 3 ( DE 3), semidiurnal eastward propagating nonmigrating tide with zonal wavenumber 2 ( SE 2), and stationary planetary wave 4 ( SPW 4). From a fixed local time perspective, the DE 3, SE 2, and SPW 4 all appear as wave‐4 structures in longitude, and thus each of these waves must be considered as a potential source of the wave‐4 variation in the ionosphere. Both the DE 3 and SPW 4 are found to produce significant wave‐4 variations in the equatorial vertical E × B drift velocity, and in the ionospheric peak density (NmF2) at 15°N magnetic latitude. The daytime wave‐4 variation in NmF2 is driven by the combination of vertical E × B drift variability and in‐situ effects due largely to meridional neutral winds. The simulation results indicate that the SE 2 is not a contributor to the wave‐4 longitude variation. Our results further demonstrate that the actual wave‐4 longitude variation is due to a combination of the DE 3 and SPW 4. We therefore conclude that, in addition to the DE 3, the SPW 4 also needs to be considered as an important driver of the wave‐4 longitude variation in the low‐latitude ionosphere. We additionally present evidence for the generation of the SPW 4 due to the nonlinear interaction between the migrating diurnal tide and the DE 3, and demonstrate the impact of DE 3 variability on the amplitude of the SPW 4.