Electric fields in the low latitude F-region

Murthy, B. V. Krishna; Hari, Sridhar

doi:10.1016/0273-1177(95)00906-x

Cited by 6 publications

(11 citation statements)

References 9 publications

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“…The vertical drift ( V d ) of the F layer during nighttime is controlled mainly by the electrodynamics once the recombination effects are accounted for [ Krishna Murthy et al ., ]. A number of workers have examined diverse aspects pertaining to the variability in V d during different geophysical conditions [ Rishbeth , ; Batista et al ., ; Abdu et al ., ; Heelis et al ., , Fejer et al ., ; Krishna Murthy and Hari , ] using limited database. The mechanism of generation of the enhancement in vertical drift just after sunset was detailed by Farley et al .…”

Section: Introductionmentioning

confidence: 99%

“…Krishna Murthy and Hari [] examined the seasonal variations of V d over the Indian sector for two high solar activity years and one low solar activity year. They showed that the seasonal mean peak V d is highest during equinoxes and least in summer in the postsunset period.…”

Section: Introductionmentioning

confidence: 99%

“…Further, they brought out the impact of neutral densities on vertical drift through modeling studies. Krishna Murthy and Hari [] have also discussed the role of sunset time in controlling seasonal peak V d during solar maximum.…”

Section: Introductionmentioning

confidence: 99%

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On the solar activity variations of nocturnal F region vertical drifts covering two solar cycles in the Indian longitude sector

2015

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A comprehensive analysis of the seasonal and solar cycle variabilities of nighttime vertical drift over the Indian longitude sector is accomplished using ionosonde data located at the magnetic equatorial location, Trivandrum (8.5°N, 76.5°E). The analysis extends over a span of two decades . The representative seasonal variations based on the extensive data of nocturnal vertical drift during three different solar activity epochs is arrived at, for the first time. Seasonally, it is seen that maximum post sunset V d is obtained in vernal equinox (VE), followed by autumnal equinox (AE), winter solstice (WS), and summer solstice (SS) for high and moderate solar epochs, while for low solar epoch, maximum V d occurs in WS followed by VE, AE, and SS. Further, the role of sunset times at the magnetic conjugate points in modulating the time and magnitude of peak drifts during different solar epochs is ascertained. The equinoctial asymmetry in peak V d during high and moderate solar epochs is another significant outcome of this study. The solar activity dependence of vertical drift for a wide range of solar fluxes has been quantified for all the seasons. In the present era of GPS-based communication and navigation, these are important results that give a better handle in understanding essential factors that impact equatorial ionospheric phenomena.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On the solar activity variations of nocturnal F region vertical drifts covering two solar cycles in the Indian longitude sector

2015

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“…This, in turn, was shown to be one of the main reasons for the day to day variability of ESF [ Sekar and Kelley , 1998]. Morphological investigations over Indian zone by Krishna Murthy and Hari [1996] reveal that although the amplitude of PRE varies depending on the solar epoch and season, PRE over Indian zone occurs generally around 1900 hours IST. Therefore the onset time of a geomagnetic storm and its effects are important to unmask the effect of perturbation electric fields on the equatorial ionospheric processes like ESF.…”

Section: Introductionmentioning

confidence: 99%

Effects of interplanetary electric field on the development of an equatorial spread F event

et al. 2006

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On a geomagnetically disturbed night (7 January 2005), an equatorial spread F (ESF) event was captured during premidnight hours by the Indian MST radar (operated in ionospheric mode) at Gadanki (13.5°N, 79.2°E, dip angle 12.5°N). The base height of the ionospheric F region over dip equator and a low‐latitude station showed similar variation during most of the ESF interval except mainly during 2145–2200 IST (Indian standard time, IST = universal time, UT + 5.5 hours). The zonal electric field variation over dip equator responded to a “prompt penetration” event at ∼2000 IST by gradually changing its polarity from westward to eastward after ∼2015 IST leading to the initiation of ESF at ∼2035 IST. The linear growth rate analysis supports the generation of irregularities only when the eastward electric field owing to the “prompt penetration” effect is taken into account. The zonal electric field became westward again after 2100 IST. However, it ephemerally turned eastward shortly after ∼2145 IST (1615 UT) that is believed to be associated with an “overshielding” condition. A plasma plume got resurrected after ∼30 min indicating the association of the development of this plume structure with the overshielding electric field. The OI 630.0 nm airglow intensity variations observed by a collocated airglow photometer, simultaneously operated in a bidirectional (zenith and east) mode, corroborated well with the ESF structure and dynamics during the disturbed period. These observations evince the active role of interplanetary electric field (IEF) in the development of ESF in the premidnight hours.

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“…Some of these are ionosondes (Abdu et al, 1981;Subbarao & Krishna Murthy, 1994;Krishna Murthy & Hari, 1996), phase path sounder (Sastri et al, 1995), and HF Doppler radar (Nair et al, 1993). Some of these are ionosondes (Abdu et al, 1981;Subbarao & Krishna Murthy, 1994;Krishna Murthy & Hari, 1996), phase path sounder (Sastri et al, 1995), and HF Doppler radar (Nair et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

On Estimation of Daytime Equatorial Vertical (E × B) Plasma Drifts Using Optical Neutral Dayglow Emission Measurements

Karan

Pallamraju

2020

JGR Space Physics

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Vertical drift (E × B) over the geomagnetic equator of the Earth is one of the fundamental parameters that governs the equatorial electrodynamics, which is responsible for the formation of large-scale phenomena in low and equatorial latitudes. We present a novel approach using ground-based optical neutral oxygen dayglow emission intensity measurements to estimate the daytime equatorial vertical drifts. The diurnal patterns of the dayglow emission intensities at OI 557.7, 630.0, and 777.4 nm wavelengths obtained from a low-latitude location, Hyderabad (78.4°E, 17.5°N; 8.9°N MLAT), India, are observed to be symmetric with respect to local noon on some days and asymmetric on some other. The extent of asymmetric nature is characterized by a parameter called Asymmetricity in Time (AT), which shows similar variations with the integrated Equatorial Electrojet (EEJ) strength. AT values obtained from the dayglow measurements are used to infer the vertical drifts. Vertical drifts derived by this method match well with the global climatological model estimates and with radar measurements. This new approach provides an alternative method for obtaining vertical drifts to enable systematic investigations of equatorial electrodynamics. Plain Language SummaryIt is well-known that the ionospheric equatorial zonal electric fields of the Earth play a key role in the generation and development of all the large-scale coupled equatorial-and low-latitude processes. Thus, knowledge of the equatorial electric fields is essential for comprehensive investigations of the equatorial-and low-latitude upper atmospheric behavior. This information on equatorial electric fields can be obtained directly by measuring the vertical drift of plasma above the magnetic equator. The vertical drifts are conventionally measured by ground-based radars and space-based payloads. In this work, a novel technique to estimate the daytime equatorial vertical drifts is presented using ground-based optical dayglow emission measurements. The estimated drifts match well with the model estimates and both ground-and space-borne observations as reported in the published literature. This method of estimating vertical drifts can be used to carry out continuous and systematic investigations of the equatorial electrodynamics. To the best of our knowledge, such a possibility of deriving the daytime equatorial vertical drifts using ground-based optical methods has not been shown before.

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Electric fields in the low latitude F-region

Cited by 6 publications

References 9 publications

On the solar activity variations of nocturnal F region vertical drifts covering two solar cycles in the Indian longitude sector

On the solar activity variations of nocturnal F region vertical drifts covering two solar cycles in the Indian longitude sector

Effects of interplanetary electric field on the development of an equatorial spread F event

On Estimation of Daytime Equatorial Vertical (E × B) Plasma Drifts Using Optical Neutral Dayglow Emission Measurements

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