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On the Role of Thermospheric Winds and Sporadic E Layers in the Formation and Evolution of Electrified MSTIDs in Geomagnetic Conjugate Regions
Author(s) -
Narayanan V. L.,
Shiokawa K.,
Otsuka Y.,
Neudegg D.
Publication year - 2018
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2018ja025261
Subject(s) - ionosonde , airglow , ionosphere , earth's magnetic field , zonal and meridional , sporadic e propagation , thermosphere , conjugate points , atmospheric sciences , amplitude , f region , middle latitudes , mesopause , northern hemisphere , conjugate , physics , geophysics , southern hemisphere , geology , climatology , electron density , electron , mesosphere , stratosphere , optics , magnetic field , mathematical analysis , mathematics , quantum mechanics , pure mathematics
Abstract The electrified medium‐scale traveling ionospheric disturbances (EMSTIDs) occurring as geomagnetically conjugate features in the middle latitude F region ionosphere are studied using multi‐instrument observations. Airglow imaging of OI 630 nm emission over Sata, Japan, and Darwin, Australia, are used to identify the occurrence of EMSTIDs. Thermospheric wind measurements made with the Fabry‐Perot interferometer observations of OI 630 nm from Shigaraki, Japan, and Darwin, Australia, are used along with ionosonde observations over Yamagawa, Japan, and Darwin, Australia, to study the thermospheric and ionospheric characteristics. These are the first results from such multi‐instrument observations simultaneously made from geomagnetic conjugate locations. Our results show that the amplitudes of the EMSTIDs are often different between the hemispheres. Thermospheric meridional winds appear to control the EMSTID amplitudes in the respective hemisphere. However, EMSTIDs are generated only when there is significant sporadic E activity with foEs often reaching greater than 6 MHz and (foEs − fbEs) reaching above 5 MHz at least for a short duration occurred. Existence of strong sporadic E activity on one of the hemispheres is found to be sufficient enough for generation of EMSTIDs in the conjugate F regions. These results conclusively indicate the importance of sporadic E layers in the generation of EMSTIDs. Further, it shows the significance of interhemispheric coupling between the E and F region ionospheres in the formation of EMSTIDs while their amplitudes in the respective hemispheres appear to have control of thermospheric neutral winds in the same hemisphere.