Typical disturbances of the daytime equatorial F region observed with a high-resolution HF radar

Blanc, E.; Houngninou, E.

doi:10.1007/s00585-998-0721-6

Cited by 7 publications

(7 citation statements)

References 20 publications

(23 reference statements)

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“…The radar echo structure is complex, but the simultaneous observation of irregularities coming from oblique and vertical directions with four radar frequencies in parallel and a high spatial resolution provide a global observation of the equatorial irregularity structure in the E and F regions of the ionosphere. The first LDG radar results present a diversity of irregularity structures in the E region between 90 and 150 km [Blanc et al, 1996] and in the F region up to 300 km [Blanc and Houngninou, 1998]. Blanc et al [1996] particularly noticed a parabolic region between 140 and 180 km in the range-time-intensity (RTI) diagram with a minimum at noon.…”

Section: Introductionmentioning

confidence: 99%

Interpretation of equatorial electrojet irregularities observed with a broad beam HF zenithal radar

Farges¹,

Blanc²,

Villain³

1999

Radio Science

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Section: Introductionmentioning

confidence: 99%

Interpretation of equatorial electrojet irregularities observed with a broad beam HF zenithal radar

Farges¹,

Blanc²,

Villain³

1999

Radio Science

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“…On that occasion, variations in the geomagnetic field and various parameters of the lowlatitude ionosphere were monitored with a view to deepening our knowledge on equatorial and low-latitude electromagnetic phenomena and underlying physical processes. Specifically, in West Africa, a network of three ionosondes, a Fabry-Pérot interferometer (Vila et al, 1998) and an HF radar (Blanc and Houngninou, 1998) were set up. In addition to those instruments, a meridian chain of 10 magnetic and telluric stations was deployed across the geomagnetic dip equator, from Lamto (Côte d'Ivoire, −6.30 • dip latitudes) to Tombouctou (Mali, +6.76 • dip latitudes), along the 5 • W meridian.…”

Section: Data and Analysismentioning

confidence: 99%

Induction effects of geomagnetic disturbances in the geo-electric field variations at low latitudes

et al. 2017

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Abstract. In this study we examined the influences of geomagnetic activity on the Earth surface electric field variations at low latitudes. During the International Equatorial Electrojet Year (IEEY) various experiments were performed along 5 • W in West Africa from 1992 to 1995. Among other instruments, 10 stations equipped with magnetometers and telluric electric field lines operated along a meridian chain across the geomagnetic dip equator from November 1992 to December 1994. In the present work, the induced effects of space-weather-related geomagnetic disturbances in the equatorial electrojet (EEJ) influence area in West Africa were examined. For that purpose, variations in the north-south (E x ) and east-west (E y ) components of telluric electric field were analyzed, along with that of the three components (H, D and Z) of the geomagnetic field during the geomagnetic storm of 17 February 1993 and the solar flare observed on 4 April 1993. The most important induction effects during these events are associated with brisk impulses like storm sudden commencement (ssc) and solar flare effect (sfe) in the geomagnetic field variations. For the moderate geomagnetic storm that occurred on 17 February 1993, with a minimum Dst index of −110 nT, the geo-electric field responses to the impulse around 11:00 LT at LAM are E x = 520 mV km −1 and E y = 400 mV km −1 . The geo-electric field responses to the sfe that occurred around 14:30 LT on 4 April 1993 are clearly observed at different stations as well. At LAM the crest-to-crest amplitude of the geo-electric field components associated with the sfe are E x = 550 mV km −1 and E y = 340 mV km −1 . Note that the sfe impact on the geoelectric field variations decreases with the increasing distance of the stations from the subsolar point, which is located at about 5.13 • N on 4 April. This trend does not reflect the sfe increasing amplitude near the dip equator due the high Cowling conductivity in the EEJ belt.

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“…During the International Equatorial Electrojet Year (IEEY), many different instruments were deployed in West Africa from 1992 to 1995 (Amory-Mazaudier et al, 1993). The campaign involved a network of three ionosondes, a Fabry-Perrot interferometer (Vila et al, 1998) and an HF radar (Blanc and Houngninou, 1998). A meridian chain of ten magnetic stations was deployed across the geomagnetic dip-equator, from -6.30° to +6.76°…”

Section: Datasets and Data Processingmentioning

confidence: 99%

“…Other studies of the equatorial F-region plasma vertical drifts were performed using various techniques of measurements. For example, Ionosondes and HF Doppler radars have been used to study the equatorial F-region vertical drifts (Namboothiri et al, 1989;Goel et al, 1990;Krishna Murthy et al, 1990;Krishna Murthy, 1995, Blanc andHoungninou, 1998). The most reliable measurements of the F-region plasma vertical drift velocity near the geomagnetic dip-equator were performed by Incoherent Scatter Radar at Jicamarca (Woodman, 1970;Farley et al, 1970 andFejer et al, 1991).…”

Section: Introductionmentioning

confidence: 99%

Estimating some parameters of the equatorial ionosphere electrodynamics from ionosonde data in West Africa

Grodji

Doumbia

Boka

et al. 2017

Advances in Space Research

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International audienceDuring the International Equatorial Electrojet Year (IEEY), an IPS-42 ionosonde located at Korhogo (9.33°N, 5.42°W, -1.88°dip-lat) and a meridian chain of 10 magnetic stations were setup in West Africa (5°West longitude). In this work, some characteristic parameters of the equatorial electrojet were estimated on the basis of the IPS-42 ionosonde data at Korhogo during the years 1993 and 1994. The study consisted of determining the zonal electric field through an estimate of the plasma vertical drift velocity. The daytime plasma vertical drift velocity was estimated from the time rates of change of the F-layer virtual height variations and a correction term that takes into account the ionization production and recombination effects. This method resulted in an improved vertical drift velocity, which was found to be comparable to the results of previous studies. The estimated vertical drift velocity was used in a semi-empirical approach which involved the IRI-2012 model for the Pedersen and Hall conductivities and the IGRF-10 model for the geomagnetic main field intensity. Thus the zonal and polarization electric fields on one hand, and the eastward Pedersen, Hall and the equatorial electrojet current densities on the other hand, were estimated. Furthermore the integrated peak current density at the EEJ center was estimated from ionosonde observations and compared with that inferred from magnetometer data. The integrated EEJ peak current densities obtained from both experiments were found to be in the same order and their seasonal variations exhibit the same trends as well

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Typical disturbances of the daytime equatorial F region observed with a high-resolution HF radar

Cited by 7 publications

References 20 publications

Interpretation of equatorial electrojet irregularities observed with a broad beam HF zenithal radar

Interpretation of equatorial electrojet irregularities observed with a broad beam HF zenithal radar

Induction effects of geomagnetic disturbances in the geo-electric field variations at low latitudes

Estimating some parameters of the equatorial ionosphere electrodynamics from ionosonde data in West Africa

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