AC electric fields associated with the plasma instabilities in the equatorial electrojet. III.

Sampath, S.; Sastry, T. S.

doi:10.5636/jgg.31.391

Cited by 7 publications

(5 citation statements)

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“…Electric field detectors using the double-probe technique have also been flown at the dip equator, although the only dc results showing the vertical (polarization) electric field have been those reported by Sartiel [1977]. Sampath and Sastry [1979] investigated wave electric fields on two noontime flights with low apogees (117 km and 128 km) and one early morning flight with a slightly higher apogee (140 km) launched from Thumba, India. (The two midday flights were actually the same as those analyzed by Sartiel [1977].)…”

mentioning

confidence: 99%

Electric field and plasma density measurements in the strongly driven daytime equatorial electrojet: 1. The unstable layer and gradient drift waves

Pfaff¹,

Kelley²,

Kudeki³

et al. 1987

J. Geophys. Res.

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Electric field and plasma density instrumentation on board a sounding rocket launched from Punta Lobos, Peru, detected intense electrostatic waves indicative of plasma instabilities in the daytime equatorial electrojet. Simultaneous measurements taken by the Jicamarca radar showed strong 3‐m type 1 electrojet echoes as well as evidence of kilometer scale horizontally propagating waves. The in situ electric field wave spectra displayed three markedly different height regions within the unstable layer: (1) a two‐stream region on the topside between 103 and 111 km where the electron current was considered to be strongest, (2) a gradient drift region between 90 and 106.5 km where the upward directed, zero‐order electron density gradient was unstable, and (3) an “interaction” region between 103 and 106.5 km where both of these instabilities were linearly unstable. The unstable altitudes and differentiation showed good agreement with the simultaneous 3‐m Jicamarca backscatter radar observations. In the region where the density gradient was unstable, large‐amplitude waves with large scale sizes (wavelengths of roughly 1–2 km) were observed. These kilometer scale waves dominated the observed in situ spectrum despite the fact that the peak in the linear gradient drift growth rate occurred at wavelengths of only a few hundred meters. Comparisons of the measured δE and δn/n components of the large‐scale waves verify the basic process inherent to the gradient drift instability: density enhancements were observed coincident with westward electric fields, and density depletions were associated with eastward fields. The amplitudes (10–15 mV/m) of these horizontal waves were strong enough to drive vertical two‐stream secondary waves. In the region where these waves existed and the electrojet current was strongest, evidence of wave steepening was seen, and the resulting waveforms of the large structures displayed a “flat‐topped” nature. In the lower region of the electrojet the irregularity power occurred over a broad range of wavelengths, estimated to be in the range of tens of meters to kilometers, and fell off rapidly for the shorter wavelengths. Throughout the gradient drift region, shorter‐scale waves often occurred in bursts which appeared controlled by the larger electric field structures.

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mentioning

confidence: 99%

Electric field and plasma density measurements in the strongly driven daytime equatorial electrojet: 1. The unstable layer and gradient drift waves

Pfaff¹,

Kelley²,

Kudeki³

et al. 1987

J. Geophys. Res.

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“…The EEJ current density is found to be about 9.6 μA/m 2 around noon hours. This value is in the range of typical daytime EEJ current density of about 8-14 μA/m 2 measured based on sounding rocket flight experiments (Sastry, 1970;Sampath & Sastry, 1979a, 1979b. The strength of counter electrojet current density is estimated to be about −5.7 μA/m 2 .…”

Section: 1029/2019ja027195mentioning

confidence: 52%

“…Sounding rocket‐borne magnetometer experiments conducted from both Indian (Sastry, ; Sampath & Sastry, ) and Peruvian (Davis et al, ; Pfaff et al, ) sectors have consistently shown that the EEJ current peaks around 105‐km altitude. However, theoretical models (Anandarao, ; Richmond, ; Sugiura & Poros, ) predict the peak of EEJ current to be around 100 km.…”

Section: Introductionmentioning

confidence: 99%

“…In the equatorial E region, a strong eastward current flows during daytime that is known as equatorial electrojet (EEJ). General characteristics of EEJ have been studied based on a large number of experiments conducted using ground-based magnetometers (e.g., Rastogi & Iyer, 1976), sounding rocket-borne magnetometers (e.g., Sampath & Sastry, 1979b;Sastry, 1970), magnetometers onboard satellites (e.g., Jadhav et al, 2002;Lühr et al, 2004), and very high frequency radar (e.g., Vikramkumar et al, 1987). Excellent reviews on this topic are available in literature (Forbes, 1981;Raghavarao & Anandarao, 1987;Yamazaki & Maute, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Altitude of Two‐Stream Irregularities in Equatorial E Region Using Sounding Rocket Experiments From Thumba

Pandey

Gupta

2020

JGR Space Physics

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Amplitudes of two-stream irregularities and equatorial electrojet (EEJ) current are known to peak around the same altitude. Sounding rocket-borne magnetometer experiments have consistently shown that the EEJ current density maximizes around 105-km altitude whereas the theoretical models predict the EEJ peak around 100 km. One of the propositions to bridge this difference in the altitude has been based on the inclusion of small-scale turbulence (wavelength of <100 m) with the large-scale dynamics (kilometer size). This proposition is examined based on in situ measurements of E region electron density and plasma irregularities (two-stream and gradient-drift irregularities) obtained at different times of the day and night. These measurements were obtained based on sounding rocket flight experiments conducted from Thumba Equatorial Rocket Launching Station (8.54 • N, 76.86 • E), a facility in the vicinity of the dip equator. Whenever two-stream irregularities are present, the minimum electrojet current density is estimated based on the threshold velocity required for generation of these plasma irregularities. This method provides estimates of nighttime E region current also, which is difficult to measure. It is found that amplitudes of both two-stream irregularities and the estimated EEJ current peak around 105-km altitude irrespective of the presence or absence of the gradient-drift irregularities at the base of electrojet (95-to 100-km altitude).

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“…( 4. ) and 41 (Maynard 1967); RFR 42, 44, 47, 50, 51 and 54 (Davis, Burrows & Stolarik 1967); RFR 45 (Shuman 1970); RFR 55 and 56 (Sastry 1973); RFR 57 and 58 ; RFR 70 to 73 (Burrows & Sastry 1976); and RFR 75 and 76 (4d) (Sampath & Sastry 1979b).…”

Section: The Modelmentioning

confidence: 99%

A study of rocket measurements of ionospheric currents-V. Modelling rocket profiles of low-latitude ionospheric current

Onwumechili

1992

Geophysical Journal International

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SUMMARY Some 25 rocket profiles of the current density of the eastward ionospheric lower current layer close to the magnetic dip equator, one profile of the reverse westward lower current layer at about 5° dip latitude and five profiles of the eastward upper current layer within 0° to about 8° dip latitude have been modelled giving the following results. The parameters of the eastward lower current layer within 0° to 2° dip latitude around local noon are; peak current density normalized to dip equator 10.4 ± 6 A km‐2, peak current intensity normalized to dip equator 145 ± 86 A km‐2, and half thickness at half of the peak current density 5.7 ± 1 km. The differences in these parameters between the equatorial electrojet in India and Peru are negligible. The parameters of the ionospheric eastward upper current layer around local noon are; peak current density normalized to the dip equator 2.37 ± 0.5 A km‐2, peak current intensity normalized to the dip equator 22.1 ± 7 A km‐2, and half thickness at half of the peak current density 4.1 ± 2 km. The parameters of the model fitting the rocket profiles extremely well have been provided. The suggestion that the lower eastward and the lower westward current layers constitute the equatorial electrojet, while the upper eastward current layer is the global part of the Sq currents, has been substantiated. This leads to results consistent with spherical harmonic analysis of geomagnetic Sq variations. The first contours of the ionospheric eastward upper current layer density have been presented and they are consistent with the features of the worldwide Sq.

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AC electric fields associated with the plasma instabilities in the equatorial electrojet. III.

Cited by 7 publications

References 5 publications

Electric field and plasma density measurements in the strongly driven daytime equatorial electrojet: 1. The unstable layer and gradient drift waves

Electric field and plasma density measurements in the strongly driven daytime equatorial electrojet: 1. The unstable layer and gradient drift waves

Altitude of Two‐Stream Irregularities in Equatorial E Region Using Sounding Rocket Experiments From Thumba

A study of rocket measurements of ionospheric currents-V. Modelling rocket profiles of low-latitude ionospheric current

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