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Wave disturbances in the low latitude ionosphere and equatorial ionospheric plasma depletions

Authors

  • J. H. A. Sobral,

  • M. A. Abdu,

  • I. S. Batista,

  • C. J. Zamlutti


Abstract

An isolated nighttime ionospheric wave disturbance was observed simultaneously by a meridional scanning 6300-Å photometer, a 6300-Å zenith photometer, a 30-MHz riometer, and an ionosonde over Cachoeira Paulista, a low-latitude station in Brazil. From the results we have identified at least two different scale sizes for the disturbances which could be broadly classified as (1) a larger scale component easily identified in the riometer data and has characteristics similar to those of a large scale TID and (2) smaller scale disturbances observable in the scanning photometer data, occurring during the ascending phases of the larger scale waves. A Fourier analysis of the zenith airglow variations clearly reveals a dominant period of about 104 min that seems to correspond to the period of the larger scale waves and no single dominant period is present for the smaller scale waves. Whereas all these have a poleward velocity component, the smaller scale waves show up this feature more markedly. The equatorial source of the smaller scale disturbances and other characteristics have led us to suggest that these disturbances are perhaps the low-latitude manifestations of the upward propagating field aligned plasma bubbles in the equatorial ionosphere.

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