The ultra-fast Kelvin waves in the equatorial ionosphere: observations and modeling

Onohara, Amelia Naomi; Batista, I. S.; Takahashi, H.

doi:10.5194/angeo-31-209-2013

Cited by 20 publications

(17 citation statements)

References 25 publications

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“…Around the same time, connections between observed UFKWs and ionospheric variability were demonstrated by several authors, including Takahashi et al (2007, 2009), Onohara et al (2013), Liu et al (2013, 2015), Gu et al (2014), and Abdu et al (2015). These works demonstrated correlations between UFKW signatures in the MLT with measurements of various F‐region ionospheric parameters.…”

Section: Introductionmentioning

confidence: 74%

Dynamics and Electrodynamics of an Ultra‐Fast Kelvin Wave (UFKW) Packet in the Ionosphere‐Thermosphere (IT)

2020

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Numerical experiments are performed using a suite of general circulation models that enable the interaction between a Kelvin wave packet and the ionosphere-thermosphere (IT) to be elucidated. Focus is on an eastward-propagating ultra-fast Kelvin wave (UFKW) packet with periods between 2 and 4 days and zonal wavenumber s = −1 during day of year (DOY) [266][267][268][269][270][271][272][273][274][275][276][277][278][279][280][281] 2009. Dissipative processes modify the classic UFKW dynamics (equatorially trapped, small meridional wind component) in three ways: (1) molecular diffusion acts to spread the UFKW zonal (u) and meridional (v) wind fields meridionally, pole to pole, as u and v, respectively, decay and grow with increasing height; (2) due to molecular diffusion, the UFKW spectrum at longer periods and with shorter vertical wavelengths preferentially dissipates with height; and (3) interaction with the diurnally varying IT introduces a westward-propagating s = +2 component to the wind field that significantly modifies its longitude-UT structure to include a diurnal modulation. The F-region ionosphere also responds with s = +2, which originates from the influence of diurnally varying E-region conductivity on E × B drifts. Additional spectral peaks in v and ionospheric parameters arise due to longitude variations in the magnetic field. Maximum excursions in NmF2 (as compared with those from a simulation without UFKW forcing) achieve values as large as ±50% but more commonly occur in the range of ±20-30%. The combination of positive and negative responses, and their relative magnitudes, depends on the phasing of the UFKW as it moves zonally relative to the Sun-synchronous diurnal variation of the ionosphere, in addition to its changing amplitude between DOY 266 and 282. Modifications of order 10 ms −1 and −7% to zonal-mean zonal winds and NmF2, respectively, also result from dissipation of the UFKW packet.

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Section: Introductionmentioning

confidence: 74%

Dynamics and Electrodynamics of an Ultra‐Fast Kelvin Wave (UFKW) Packet in the Ionosphere‐Thermosphere (IT)

2020

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“…This interpretation should hold also for vertical drift oscillation induced by a UFK wave through its modulation of the E region zonal wind. In a recent study, Onohara et al (2013) used an E-F layer electrical coupling model (Heelis et al 1974;Batista et al 1986) in which the E layer tidal zonal winds and F layer dynamo electric fields produced the PRE vertical drift velocity. By superposing a UFK wave type oscillation on the E layer tidal wind, they obtained the F region evening vertical drift oscillation compatible with the drift oscillation observed due to the passage of a UFK wave.…”

Section: Discussionmentioning

confidence: 99%

Fast and ultrafast Kelvin wave modulations of the equatorial evening F region vertical drift and spread F development

et al. 2015

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In this paper, we investigate the role of eastward and upward propagating fast (FK) and ultrafast Kelvin (UFK) waves in the day-to-day variability of equatorial evening prereversal vertical drift and post sunset generation of spread F/plasma bubble irregularities. Meteor wind data from Cariri and Cachoeira Paulista (Brazil) and medium frequency (MF) radar wind data from Tirunelveli (India) are analyzed together with Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry (TIMED/SABER) temperature in the 40-to 100-km region to characterize the zonal and vertical propagations of these waves. Also analyzed are the F region evening vertical drift and spread F (ESF) development features as diagnosed by Digisonde (Lowell Digisonde International, LLC, Lowell, MA, USA) operated at Fortaleza and Sao Luis in Brazil. The SABER temperature data permitted determination of the upward propagation characteristics of the FK (E1) waves with propagation speed in the range of 4 km/day. The radar mesosphere and lower thermosphere (MLT) winds in the widely separated longitude sectors have yielded the eastward phase velocity of both the FK and UFK waves. The vertical propagation of these waves cause strong oscillation in the F region evening prereversal vertical drift, observed for the first time at both FK and UFK periodicities. A delay of a few (approximately 10) days is observed in the F region vertical drift perturbation with respect to the corresponding FK/UFK zonal wind oscillations, or temperature oscillations in the MLT region, which has permitted a direct identification of the sunset electrodynamic coupling process as being responsible for the generation of the FK/UFK-induced vertical drift oscillation. The vertical drift oscillations are found to cause significant modulation in the spread F/plasma bubble irregularity development. The overall results highlight the role of FK/UFK waves in the day-to-day variability of the ESF in its occurrence season.

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“…Experimental measurements and numerical modeling have shown the influence of the UFKW in the day-to-day variability of the equatorial ionosphere England et al, 2012;Onohara et al, 2013). One possible way for the planetary-scale waves to communicate their signatures to the ionosphere is through modulations of the atmospheric tides, which are able to penetrate into the ionosphere.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast Kelvin waves in the MLT airglow and wind, and their interaction with the atmospheric tides

et al. 2018

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Abstract. Airglow and wind measurements from the Brazilian equatorial region were used to investigate the presence and the effects of the 3-4-day ultrafast Kelvin waves in the MLT. The airglow integrated intensities of the OI557.7 nm, O 2 b(0-1) and OH(6-2) emissions, as well as the OH rotational temperature, were measured by a multichannel photometer, and the zonal and meridional wind components between 80 and 100 km were obtained from a meteor radar. Both instruments are installed in the Brazilian equatorial region at São João do Cariri (7.4 • S, 36.5 • W). Data from 2005 were used in this study. The 3-4-day oscillations appear intermittently throughout the year in the airglow. They were identified in January, March, July, August and October-November observations. The amplitudes induced by the waves in the airglow range from 26 to 40 % in the OI557.7 nm, 17 to 43 % in the O 2 b(0-1) and 15 to 20 % in the OH(6-2) emissions. In the OH rotational temperature, the amplitudes were from 4 to 6 K. Common 3-4-day oscillations between airglow and neutral wind compatible with ultrafast Kelvin waves were observed in March, August and October-November. In these cases, the amplitudes in the zonal wind were found to be between 22 and 28 m s −1 and the vertical wavelength ranges from 44 to 62 km. Evidence of the nonlinear interaction between the ultrafast Kelvin wave and diurnal tide was observed.

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The ultra-fast Kelvin waves in the equatorial ionosphere: observations and modeling

Cited by 20 publications

References 25 publications

Dynamics and Electrodynamics of an Ultra‐Fast Kelvin Wave (UFKW) Packet in the Ionosphere‐Thermosphere (IT)

Dynamics and Electrodynamics of an Ultra‐Fast Kelvin Wave (UFKW) Packet in the Ionosphere‐Thermosphere (IT)

Fast and ultrafast Kelvin wave modulations of the equatorial evening F region vertical drift and spread F development

Ultrafast Kelvin waves in the MLT airglow and wind, and their interaction with the atmospheric tides

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