Abstract
Abstract. The main purpose of this study is to investigate the vertical coupling between the mesosphere and lower thermosphere (MLT) region and the ionosphere through ultra-fast Kelvin (UFK) waves in the equatorial atmosphere. The effect of UFK waves on the ionospheric parameters was estimated using an ionospheric model which calculates electrostatic potential in the E-region and solves coupled electrodynamics of the equatorial ionosphere in the E- and F-regions. The UFK wave was observed in the South American equatorial region during February–March 2005. The MLT wind data obtained by meteor radar at São João do Cariri (7.5° S, 37.5° W) and ionospheric F-layer bottom height (h'F) observed by ionosonde at Fortaleza (3.9° S; 38.4° W) were used in order to calculate the wave characteristics and amplitude of oscillation. The simulation results showed that the combined electrodynamical effect of tides and UFK waves in the MLT region could explain the oscillations observed in the ionospheric parameters.
Highlights
IntroductionIntroduction oscillations in bothMLT and ionosphere obserDvaistciousnssi.oTnsaka-Iiwnnasvitghenseifiemcqaoundatet,ostrhibaelecKaotemmlveoisnpimhweparovere,tsaw,nhatMse(rwHeoeotdlhllteoeanslC, oDRG1ro9ieos9elsv2ibos)ey.sf-logKocrrceaipeelvvimnitinysteifnicthwsapnaihsdnhedfiroidecFat2tpaaal(.rfFar(om2lma0ey0teeS7rr)asocarphJiptoiFlcaiaeo(ldMmdfworineoaCqivmduaeeurleienmrtcliya(DF)Gn7a.me4lleya◦evysoaSieess,rsul3trocov6eDid.ipmri5est◦ucbmenuayWtesltesoai)hifr,oniednircioistaggndhioast--r) waves are due to the change in the Coriolis parameter near sonde installed at Fortaleza (3.9◦ S, 38.4◦ W), and temperathe equator and are considered to be a special kind of grav- ture data from the TIMED/SABER satellite in order to invesity wave modified by the Earth’s rotationH(Aynddrreowlsoegt yal.,andtigate UFK wave oscillations in boHthymdesrooslpohegriyc aannd diono- 1987). ducingThese waves perturbations are trapped in the in the zonal wind veeqluoactEiotyrai,atrletmrhepgeiSoranytuisnre-temsdpehnecreicofpaprraompaegteartsio. nThoifs awUasFKthewfiavrEsetafrreroptmohrtthSoefysatsracttleoeasmpr heevrieand geopotential fields, and the phase propagates eaSstcwiaerdns.ces
In order to test the influence of different wind amplitude on the F-layer vertical drifts, we considered four different conditions for the upward propagating wave: (1) exponential growth of the wave amplitude from 90 to 120 km altitude, (2) a 50 % attenuation applied to the exponential growth factor, (3) a 75 % attenuation applied to the exponential growth factor, and (4) no exponential growth but a constant amplitude with height
In the present study it was possible to verify that the superposition of UFK and tidal waves in the generation of the ionospheric E-region dynamo is capable of modulating the diurnal tide as well as generating semidiurnal tides and, further, two day wave signatures in ionospheric vertical drift
Summary
Introduction oscillations in bothMLT and ionosphere obserDvaistciousnssi.oTnsaka-Iiwnnasvitghenseifiemcqaoundatet,ostrhibaelecKaotemmlveoisnpimhweparovere,tsaw,nhatMse(rwHeoeotdlhllteoeanslC, oDRG1ro9ieos9elsv2ibos)ey.sf-logKocrrceaipeelvvimnitinysteifnicthwsapnaihsdnhedfiroidecFat2tpaaal(.rfFar(om2lma0ey0teeS7rr)asocarphJiptoiFlcaiaeo(ldMmdfworineoaCqivmduaeeurleienmrtcliya(DF)Gn7a.me4lleya◦evysoaSieess,rsul3trocov6eDid.ipmri5est◦ucbmenuayWtesltesoai)hifr,oniednircioistaggndhioast--r) waves are due to the change in the Coriolis parameter near sonde installed at Fortaleza (3.9◦ S, 38.4◦ W), and temperathe equator and are considered to be a special kind of grav- ture data from the TIMED/SABER satellite in order to invesity wave modified by the Earth’s rotationH(Aynddrreowlsoegt yal.,andtigate UFK wave oscillations in boHthymdesrooslpohegriyc aannd diono- 1987). ducingThese waves perturbations are trapped in the in the zonal wind veeqluoactEiotyrai,atrletmrhepgeiSoranytuisnre-temsdpehnecreicofpaprraompaegteartsio. nThoifs awUasFKthewfiavrEsetafrreroptmohrtthSoefysatsracttleoeasmpr heevrieand geopotential fields, and the phase propagates eaSstcwiaerdns.ces. Iiwnnasvitghenseifiemcqaoundatet,ostrhibaelecKaotemmlveoisnpimhweparovere,tsaw,nhatMse(rwHeoeotdlhllteoeanslC, oDRG1ro9ieos9elsv2ibos)ey.sf-logKocrrceaipeelvvimnitinysteifnicthwsapnaihsdnhedfiroidecFat2tpaaal(.rfFar(om2lma0ey0teeS7rr)asocarphJiptoiFlcaiaeo(ldMmdfworineoaCqivmduaeeurleienmrtcliya(DF)Gn7a.me4lleya◦evysoaSieess,rsul3trocov6eDid.ipmri5est◦ucbmenuayWtesltesoai)hifr,oniednircioistaggndhioast--r) waves are due to the change in the Coriolis parameter near sonde installed at Fortaleza (3.9◦ S, 38.4◦ W), and temperathe equator and are considered to be a special kind of grav- ture data from the TIMED/SABER satellite in order to invesity wave modified by the Earth’s rotationH(Aynddrreowlsoegt yal.,andtigate UFK wave oscillations in boHthymdesrooslpohegriyc aannd diono- 1987). Onohara et al.: The ultra-fast Kelvin waves in the equatorial ionosphere to the ionosphere. From the characteristics of the downward phase propagation (wavelength ∼ 40 km), longitudinal and latitudinal extension, the authors concluded that the oscillation was compatible with a 3.5-day Ultra Fast Kelvin wave. The results revealed UFK wave modulations, reinforcing the importance of this kind of wave in the coupling between the neutral and ionized atmosphere
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