Ionisation ledges in the equatorial ionosphere

Raghavarao, R.; Sivaraman, M. R.

doi:10.1038/249331a0

Cited by 34 publications

(41 citation statements)

References 3 publications

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“…6, our results indicated that peaks of some ledge structures locate on the field line anchored at higher latitude than the crest. This result differs from those reported by Raghavarao and Sivaraman (1974); they reported that the peak of the ledge structure and the crest of the equatorial anomaly existed on the same field line until about 16 LT. The occurrence probability of the ledge structure obtained in the present study is higher than the previous statistical result (216 of 577 days (37%) (Sharma, and Raghavarao, 1989 namely, our result shows the tendency that occurrence probability becomes higher at equinox, and lower at solstice while their results shows that it is higher at solstice and lower at equinox.…”

Section: Analysis and Resultscontrasting

confidence: 56%

“…The ionization ledge has been identified as an ionization enhancement with about 10% from the ambient plasma located within the region of the equatorial anomaly. At the magnetic equator height of the ledge increases from about 500 km at 12 LMT to 900 km at 22 LMT (Lockwood and Nelms, 1964;Raghavarao and Sivaraman, 1974). Sharma and Raghavarao (1989) suggested that until about 16 LT, both the peak of the ionization ledge and the anomaly crest are located aligned along the same field line, and then, they become to be separated each other.…”

Section: Introductionmentioning

confidence: 99%

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Ionization ledge structures observed in the equatorial anomaly region by using PPS system on-board the Ohzora (EXOS-C) satellite

et al. 2014

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To verify an additional ionization layer predicted in the equatorial ionosphere, topside ionograms obtained by the Planetary Plasma Sounder (PPS) system on-board the Ohzora (EXOS-C) satellite were analyzed. Based on the analysis of the PPS data of 8 passes in March and 11 passes in May, 1987, the ionization ledge observed in the local noon time period shows similar nature as it has been theoretically predicted for the F 3 layer by Balan and Bailey (1995). It was noted that some peaks of the ledge structure were located on the field line of higher latitude region than the field line of the crest of the equatorial anomaly.

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Section: Analysis and Resultscontrasting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Ionization ledge structures observed in the equatorial anomaly region by using PPS system on-board the Ohzora (EXOS-C) satellite

et al. 2014

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“…Under the influence of this E field and the magnetic field (B) of the Earth, the F-region plasma over the magnetic equator moves upward due to E × B drift. This plasma then diffuses along the magnetic field lines and accumulates at around ±15°latitudes off the magnetic equator, building up regions of enhanced densities (crests) in plasma, and this phenomenon is known as the EIA (Raghavarao et al 1988). The strength and latitude coverage of the EIA crest depends on season and lower atmospheric forcings of tidal nature (Immel et al 2006;Pallamraju et al 2004Pallamraju et al , 2010.…”

Section: Resultsmentioning

confidence: 99%

Vertical coupling of atmospheres: dependence on strength of sudden stratospheric warming and solar activity

Laskar

Pallamraju

Veenadhari³

2014

Earth Planet Sp

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Comprehensive behavior of the low-latitude upper atmosphere during sudden stratospheric warming (SSW) events at varying levels of solar activity has been investigated. The equatorial electrojet (EEJ) strength and the total electron content (TEC) data from low latitudes over Indian longitudes during the mid-winter season in the years 2005 to 2013 are used in this study. Five major and three minor SSW events occurred in the observation duration, wherein the solar activity had varied from minimum (almost no sunspots) to mini-maximum (approximately 50 sunspots of the solar cycle 24). Spectral powers of the large-scale planetary wave (PW) features in the EEJ and the TEC have been found to be varying with solar activity and SSW strengths. Specially, the spectral powers of quasi-16-day wave variations during the three very strong SSW events in the years 2006, 2009, and 2013 were found to be very high in comparison with those of other years. For these major events, the amplitudes of the semi-diurnal tides and quasi-16-day waves were found to be highly correlated and were maximum around the peak of SSW, suggesting a strong interaction between the two waves. However, this correlation was poor and the quasi-16-day spectral power was low for the minor events. A strong coupling of atmospheres was noted during a relatively high solar activity epoch of 2013 SSW, which was, however, explained to be due to the occurrence of a strong SSW event. These results suggest that the vertical coupling of atmospheres is stronger during strong major SSW events and these events play an important role in enabling the coupling even during high solar activity.

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“…Raghavarao and Sivaraman [20] detected the afternoon ledges in the Indian longitudes using the ISIS-II topside sounder data collected at Ahmedabad (32.1 • N, 44.3 • E; 26.9…”

Section: Satellite Observationmentioning

confidence: 99%

Stratification of the Low-Latitude and Near-EquatorialF2Layer, Topside Ionization Ledge, andF3Layer: What We Know about This? A Review

Клименко¹,

Karpachev²,

Клименко³

2012

International Journal of Geophysics

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A large number of researches have been devoted to the formation of additional layers in the F region of the equatorial ionosphere, first of which has been published in 1940s. Originally the occurrence of such layer was named "stratification of equatorial F2 layer." The additional layer was later named as the F3 layer. The theoretical researches have shown that the F3 layer is formed by zonal component of electric field with assistance of meridional component of thermospheric wind and field-aligned plasma diffusion. The physical mechanism of the F3 layer formation is clearly formulated for the morning-noon period, although the F3 layer is also observed at other hours. This paper presents a brief review into the history of the additional layer researches, describes the current progress of these researches, and identifies the most important problems in this field of the ionospheric physics.

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Ionisation ledges in the equatorial ionosphere

Cited by 34 publications

References 3 publications

Ionization ledge structures observed in the equatorial anomaly region by using PPS system on-board the Ohzora (EXOS-C) satellite

Ionization ledge structures observed in the equatorial anomaly region by using PPS system on-board the Ohzora (EXOS-C) satellite

Vertical coupling of atmospheres: dependence on strength of sudden stratospheric warming and solar activity

Stratification of the Low-Latitude and Near-EquatorialF2Layer, Topside Ionization Ledge, andF3Layer: What We Know about This? A Review

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