Planetary wave-tidal interactions over the equatorial mesosphere-lower thermosphere region and their possible implications for the equatorial electrojet

Vineeth, C.; Pant, Tarun Kumar; Sumod, S. G.; Kumar, Karanam Kishore; Gurubaran, S.; Sridharan, R.

doi:10.1029/2010ja015895

Cited by 18 publications

(25 citation statements)

References 35 publications

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“…A similar mechanism has been suggested to explain day‐to‐day variability in the temperature and wind fields in the mesosphere [ Anderson et al, ]. The influence of tides, gravity, and planetary waves propagating into the mesosphere, which have sources in the troposphere and stratosphere can contribute significantly to alter even the averaged characteristics of the EEJ [ Reddy and Devasia, ; Raghavarao and Anandarao, 1980 ; Somayajulu et al, ; Gurubaran, ; Abdu et al, ; Liu and Watanabe , ; Ramkumar et al ; Vineeth et al, , , ].The influence of local land‐sea and topographic contrasts has been pointed in theoretical work for the eastward propagating diurnal tide, results significant longitudinal variation in the local time EEJ variation [ England et al, ; Forbes et al, ]. However, detailed concurrent studies are required to correlate ionospheric observations with EEJ strength at closely spaced longitudes is yet to be carried out.…”

Section: Discussionmentioning

confidence: 80%

“…Several earlier studies sought explanations for these differences by correlating them with direct observations of ionospheric processes. Locally significant effects have been observed using optical airglow instrument, MF radar and found to correlate closely with the occurrence of CEJs at Trivandrum [ Ramkumar et al, ; Sridharan et al, ; Vineeth et al, , ], resulting the lowering of EEJ amplitude. The occurrence of CEJ results in the depression of the noontime EEJ by about 50% of its strength (Figure ) [ Somayajulu et al, ].…”

Section: Discussionmentioning

confidence: 99%

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Characterization of seasonal and longitudinal variability of EEJ in the Indian region

2014

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This paper presents the seasonal and longitudinal variability of the equatorial electrojet (EEJ) based on geomagnetic variation data from two electrojet stations in the northern Indian Ocean at a longitudinal separation of~15°: i.e., at 77°E and at 93°E. One complete year of data is used (i.e., from November 2011 to October 2012) at the two longitudes and compared with the climatological model of the equatorial electrojet (EEJM-2.0). The results of our analysis show that (i) the monthly averaged hourly values of EEJ strength at 77°E and 93°E are overall in agreement with global characteristics of EEJ with significant departures over the year of study, (ii) the monthly average hourly daytime values at Campbell Bay and Vencode show poor correlation (r < 0.7) for 5 out of 10 months, (iii) comparison of observed EEJ strength at respective longitudes and the current densities derived from EEJM-2.0 show overall agreement with significant differences for monthly mean hourly daytime values at respective longitudes, and (iv) day-to-day variability in noontime EEJ amplitudes between the two longitudes is >10 nT, >20 nT for 30% of quiet days, sorted by planetary index (Kp) <1 and <2. This variability is reflected in monthly average values (V) mechanisms for persistent differences in EEJ on day-to-day basis are sought from perturbation of westward ion drifts by neutral winds caused by the upward propagation of gravity waves from troposphere/stratosphere into the mesosphere. These mechanisms have been identified theoretically and experimentally. The four-wave structure of ionospheric current densities obtained by EEJM-2.0 and other contemporary models closely resembles atmospheric tidal signatures and has a common origin. The magnitude and persistence of these differences, at short spatial scales (15°), are significant observation. These effects are reflected in the monthly and seasonal signatures of EEJ and contribute to the contemporary models.

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Section: Discussionmentioning

confidence: 80%

Section: Discussionmentioning

confidence: 99%

Characterization of seasonal and longitudinal variability of EEJ in the Indian region

2014

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“…The scatter in CEJ amplitude distribution is larger than the scatter of EEJ amplitude at 5° spatial separations (Figure and ), implying that CEJ is caused by shorter‐scale phenomena (~100, 1,000 km), where as the EEJ is driven by stronger effects, with large spatial scale length (Lühr et al, ). Experimental evidence of the short‐scale length perturbations were also obtained by direct measurements of wind and temperature in mesosphere (Abdu et al, ; Karan & Pallamraju, ; Tsuda, ; Vineeth et al, ).…”

Section: Discussionmentioning

confidence: 86%

Constraints on Scale Lengths of Equatorial Electrojet and Counter Electrojet Phenomena From the Indian Sector

et al. 2018

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The present study investigates the longitudinal variability of equatorial electrojet (EEJ) and counter electrojet (CEJ) phenomena using concurrent data from three equatorial and low‐latitude paired stations/sites at 5°, 15°, and 20° longitudinal separation in the Indian sector: (i) Minicoy (72°E, dip latitude 01.32°) and Alibag (72°E, dip latitude 14.06°), (ii) Vencode (77°E, dip latitude 01.02°) and Hyderabad (77°E, dip latitude12.34°), and (iii) Campbell Bay (93°E, dip latitude −0.79°) and Nabagram (93°E, dip latitude 06.79°). The observations, over a period of 12 months, at 72°E and 77°E, and 10 months at 93°E, for the year 2015, reflect the variability in both amplitude and occurrence phenomena at close spatial scales. Significant day‐to‐day variability of EEJ and CEJ is observed, with increasing spatial separation. The closely spaced sites, MNC and VEN, show expected similarity but present striking differences in certain monthly averaged patterns. Concurrent observations from three longitudes reveal increasing EEJ amplitudes from west to east and a new observation of increasing CEJ amplitudes from east to west. From these longitudinal trends, we confirm that EEJ strengths are controlled by the large‐scale DE3 nonmigrating tide. A marked difference in CEJ amplitude between MNC and VEN suggests that scale lengths of CEJ and EEJ are different, and we infer that CEJ are primarily generated by short‐scale length variations in the middle atmosphere caused by localized interactions of planetary and gravity waves and are also influenced by the DE3 nonmigrating tide.

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“…Considerable observational evidence [ Fritts and Vincent , 1987; Teitelbaum et al , 1989; Manson et al , 1998; Pancheva , 2000, 2006; Pancheva et al , 2000; Haldoupis et al , 2004; Vineeth et al , 2011] has revealed that wave–wave interactions among tides, GWs, and PWs are ubiquitous in the mesosphere and lower thermosphere and play an important role in determining atmospheric structure and disturbances. Therefore such interactions have become subject of a great deal of theoretical interest [ Fritts and Vincent , 1987; Teitelbaum et al , 1989; Miyahara and Forbes , 1991; Liu and Hagan , 1998; Mayr et al , 1998; Smith and Ortland , 2001; Chang et al , 2011].…”

Section: Introductionmentioning

confidence: 99%

Atmospheric waves and their interactions in the thermospheric neutral wind as observed by the Arecibo incoherent scatter radar

et al. 2012

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[1] Atmospheric waves and their interactions in the thermospheric neutral wind are studied based on Arecibo incoherent scatter radar observations. Our analysis suggests that the thermospheric atmosphere is usually disturbed by certain types of waves, including tides, gravity waves, and planetary waves, of which the diurnal tide is almost always the dominant disturbance. Strong interactions (defined as the coexistence of strong positive and negative correlations among the interacting waves) between the diurnal tide and gravity waves are frequently observed during the entire observation period. These strong interactions can persist for several days, although they are highly intermittent. Moreover, the sum and difference interactions between the diurnal tide and gravity waves always occur simultaneously and the energy exchange between the interacting waves is sometimes reversible. In addition to tide-gravity wave interactions, tide-planetary wave and tide-tide interactions are also found in our data. In tide-planetary wave interactions, the tidal oscillations are modulated at the interacting planetary wave periods. A combination of bispectral and correlation analyses verifies the occurrence of nonlinear interactions among different tidal components in the middle thermosphere. Moreover, during tide-tide interactions, the energy transfer trend changes very frequently, indicating that tidal energy is frequently redistributed among different tidal components. Generally, our study provides proof of strong tide-gravity wave, tide-planetary wave, and tide-tide interactions in the middle thermosphere, which has rarely been reported to date.

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Planetary wave-tidal interactions over the equatorial mesosphere-lower thermosphere region and their possible implications for the equatorial electrojet

Cited by 18 publications

References 35 publications

Characterization of seasonal and longitudinal variability of EEJ in the Indian region

Characterization of seasonal and longitudinal variability of EEJ in the Indian region

Constraints on Scale Lengths of Equatorial Electrojet and Counter Electrojet Phenomena From the Indian Sector

Atmospheric waves and their interactions in the thermospheric neutral wind as observed by the Arecibo incoherent scatter radar

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