scholarly journals The Influence of Disturbance Dynamo Electric Field in the Formation of Strong Sporadic E Layers Over Boa Vista, a Low‐Latitude Station in the American Sector

2020 ◽  
Vol 125 (7) ◽  
Author(s):  
L. C. A. Resende ◽  
J. K. Shi ◽  
C. M. Denardini ◽  
I. S. Batista ◽  
P. A. B. Nogueira ◽  
...  
Keyword(s):  
Electric Field ◽  
Low Latitude ◽  
Latitude Station ◽  
Sporadic E Layers ◽  
Sporadic E

Storm-time Disturbed Electric Field Influence in the Strong Sporadic E-layers Occurrence over Boa Vista, a low latitude Brazilian Region

2019 ◽  
Author(s):  
Laysa Cristina Araujo Resende ◽  
Shi Jiankui ◽  
Clezio Marcos Denardini ◽  
Paulo Alexandre Bronzato Nogueira ◽  
Inez S. Batista ◽  
...  
Keyword(s):  
Electric Field ◽  
Low Latitude ◽  
Sporadic E Layers ◽  
Sporadic E ◽  
Field Influence

scholarly journals Study of sporadic E layers based on GPS radio occultation measurements and digisonde data over the Brazilian region

2018 ◽  
Vol 36 (2) ◽  
pp. 587-593 ◽  
Author(s):  
Laysa C. A. Resende ◽  
Christina Arras ◽  
Inez S. Batista ◽  
Clezio M. Denardini ◽  
Thainá O. Bertollotto ◽  
...  
Keyword(s):  
Radio Occultation ◽  
Signal To Noise Ratio ◽  
Satellite Measurements ◽  
Low Latitude ◽  
Middle Latitudes ◽  
Sporadic E Layers ◽  
Sporadic E ◽  
Comparative Results ◽  
Layer Development ◽  
Good Agreement

Abstract. This work presents new results about sporadic E-layers (Es layers) using GPS (global positioning system) radio occultation (RO) measurements obtained from the FORMOSAT-3/COSMIC satellites and digisonde data. The RO profiles are used to study the Es layer occurrence as well as its intensity of the signal-to-noise ratio (SNR) of the 50 Hz GPS L1 signal. The methodology was applied to identify the Es layer on RO measurements over Cachoeira Paulista, a low-latitude station in the Brazilian region, in which the Es layer development is not driven tidal winds only as it is at middle latitudes. The coincident events were analyzed using the RO technique and ionosonde observations during the year 2014 to 2016. We used the electron density obtained using the blanketing frequency parameter (fbEs) and the Es layer height (h'Es) acquired from the ionograms to validate the satellite measurements. The comparative results show that the Es layer characteristics extracted from the RO measurements are in good agreement with the Es layer parameters from the digisonde. Keywords. Ionosphere (ionosphere–atmosphere interactions)

scholarly journals High resolution observations of sporadic-E layers within the polar cap ionosphere using a new incoherent scatter radar experiment

2002 ◽  
Vol 20 (9) ◽  
pp. 1429-1438 ◽  
Author(s):  
B. Damtie ◽  
T. Nygrén ◽  
M. S. Lehtinen ◽  
A. Huuskonen
Keyword(s):  
High Resolution ◽  
Electric Field ◽  
Single Layer ◽  
Meridional Wind ◽  
Two Phase ◽  
Range Resolution ◽  
Incoherent Scatter ◽  
Sporadic E Layers ◽  
Sporadic E ◽  
Ionospheric Electric Field

Abstract. High resolution observations of sporadic-E layers using a new experiment with the EISCAT (European Incoherent SCATter) Svalbard radar (ESR) are presented. The observations were made by means of a new type of hardware, which was connected in parallel with the standard receiver. The radar beam was aligned with the geomagnetic field. The experiment applies a new modulation principle. Two phase codes, one with 22 bits and the other with 5 bits, were transmitted at separate frequencies. Each bit was further modulated by a 5-bit Barker code. The basic bit length of both transmissions was 6 µs. Instead of storing the lagged products of the ionospheric echoes in the traditional way, samples of both the transmitted pulses and the ionospheric echoes were taken at intervals of 1 µs and stored on hard disk. The lagged products were calculated later in an off-line analysis. In the analysis a sidelobe-free Barker decoding technique was used. The experiment produces range ambiguities, which were removed by mathematical inversion. Sporadic-E layers were observed at 105–115 km altitudes, and they are displayed with a 150-m range resolution and a 10-s time resolution. The layers show sometimes complex shapes, including triple peaked structures. The thickness of these sublayers is of the order of 1–2 km and they may be separated by 5 km in range. While drifting downwards, the sublayers merge together to form a single layer. The plasma inside a layer is found to have a longer correlation length than that of the surrounding plasma. This may be an indication of heavy ions inside the layer. The field-aligned ion velocity is also calculated. It reveals shears in the meridional wind, which suggests that shears probably also exist in the zonal wind. Hence the wind shear mechanism is a possible generation mechanism of the layer. However, observations from the coherent SuperDARN radar indicate the presence of an ionospheric electric field pointing in the sector between west and north. Thus, the layer could also be produced by the electric field mechanism. This means that both mechanisms may be active simultaneously. Their relative importance could not be determined in this study.Key words. Ionosphere; polar ionosphere, instruments and techniques

scholarly journals HF Doppler radar observations of sporadic E at an Indian low latitude station, Visakhapatnam

2009 ◽  
Vol 27 (2) ◽  
pp. 537-545 ◽  
Author(s):  
M. S. S. R. K. N Sarma ◽  
C. Raghava Reddy ◽  
K. Niranjan
Keyword(s):  
Doppler Radar ◽  
Doppler Velocity ◽  
Night Time ◽  
Low Latitude ◽  
Radar Observations ◽  
Latitude Station ◽  
Velocity Variations ◽  
Sporadic E ◽  
Gradient Drift ◽  
Drift Instability

Abstract. 5.5 MHz HF Doppler radar observations of Sporadic E over an Indian low latitude station, Visakhapatnam (17.7° N, 83.3° E and Dip 20°) with 10 s resolution showed quasi-periodic variations of the echo strength and Doppler velocity variations with periods of a few minutes to a few tens of minutes. The echo strength and Doppler velocity variations with time in different range bins of the ES echo showed variations which are some times similar and some times significantly different in successive range bins at intervals of 7.5 km. The ES echo occurs with the height of maximum echo strength in the range of 100 km to 120 km and some times at 130 km. The altitude variation of the average Doppler velocity is highly variable and the height of maximum echo strength is not the same as the height of maximum Doppler velocity. Observations of ES echoes at different times of the day are presented to bring out the differences between the day and night time ES echoes. The relationship between Radar and ES parameters derived from Ionograms is poorer than that of mid latitudes which is quite consistent with the expectations based on gradient drift instability.

scholarly journals A comparative study of atmospheric Maxwell current and electric field from a low latitude station, Tirunelveli

2003 ◽  
Vol 55 (11) ◽  
pp. 697-703 ◽  
Author(s):  
C. Panneerselvam ◽  
K. U. Nair ◽  
K. Jeeva ◽  
C. Selvaraj ◽  
S. Gurubaran ◽  
...  
Keyword(s):  
Electric Field ◽  
Comparative Study ◽  
Low Latitude ◽  
Latitude Station

scholarly journals The role of electric field and neutral wind in the generation of polar cap sporadic E

2008 ◽  
Vol 26 (12) ◽  
pp. 3757-3763 ◽  
Author(s):  
T. Nygrén ◽  
M. Voiculescu ◽  
A. T. Aikio
Keyword(s):  
Electric Field ◽  
Driving Forces ◽  
Neutral Wind ◽  
Polar Cap ◽  
Sporadic E Layers ◽  
Sporadic E ◽  
In The Beginning ◽  
Model Formation ◽  
Good Agreement

Abstract. This paper investigates the roles of electric field and neutral wind in the generation of sporadic-E layers within the polar cap. Two Es layers above Svalbard, observed by the EISCAT Svalbard Radar (ESR), were chosen for investigation. The radar experiment contains four beam directions, and this was used for determining the electric field. The neutral wind was obtained from the HWM93 model. Formation of Es layers was calculated by integrating the continuity equation under the action of driving forces due to neutral wind and electric field. A flat height profile of metal ions was assumed in the beginning. The calculation gives the time variation of the layer, which can be compared with observations. In one case the electric field was shown to be the main driving agent in layer generation. In the other case the electric field was weak and the layer was produced mainly by the neutral wind, but the electric field had influence on the height of the layer. A fairly good agreement between the variations of the observed and calculated layer altitudes was obtained and some agreement between the intensity variations was also found.

scholarly journals Sporadic sodium layer: A possible tracer for the conjunction between the upper and lower atmospheres

2020 ◽  
Author(s):  
Shican Qiu ◽  
Ning Wang ◽  
Willie Soon ◽  
Gaopeng Lu ◽  
Mingjiao Jia ◽  
...  
Keyword(s):  
Electric Field ◽  
World Wide ◽  
Atmospheric Electric Field ◽  
Fluxgate Magnetometer ◽  
Ionospheric Disturbances ◽  
Sodium Layer ◽  
Sporadic E Layers ◽  
Sporadic E ◽  
Statistical Results

Abstract. In this research, we reveal the inter-connection between lightning strokes, reversal of the electric field, ionospheric disturbances, and a trigger of sporadic sodium layer event (NaS), based on the joint observations by three lidars, an ionosonde, an atmospheric electric mill, a fluxgate magnetometer, and World Wide Lightning Location Network (WWLLN). Our results suggest that lightning strokes would probably have an influence on the ionosphere and thus give rise to the occurrence of NaS, with the overturning of electric field playing an important role. Statistical results reveal that the sporadic E layers (ES) could hardly be formed or maintained when the atmospheric electric field turns upward. A conjunction between the lower and upper atmospheres could be established by these inter-connected phenomena, and the key processes could be suggested as follows: lightning strokes→overturning of electric field→different collisional frequencies for ions and electrons→depletion of ES/generation of NaS.

scholarly journals IMF effect on sporadic-E layers at two northern polar cap sites: Part I – Statistical study

2006 ◽  
Vol 24 (3) ◽  
pp. 887-900 ◽  
Author(s):  
M. Voiculescu ◽  
A. T. Aikio ◽  
T. Nygrén ◽  
J. M. Ruohoniemi
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Statistical Study ◽  
Polar Cap ◽  
Sporadic E Layers ◽  
Convection Model ◽  
Sporadic E ◽  
The Relationship ◽  
Electric Field Mechanism ◽  
The Imf

Abstract. In this paper we investigate the relationship between polar cap sporadic-E layers and the direction of the interplanetary magnetic field (IMF) using a 2-year database from Longyearbyen (75.2 CGM Lat, Svalbard) and Thule (85.4 CGM Lat, Greenland). It is found that the MLT distributions of sporadic-E occurrence are different at the two stations, but both are related to the IMF orientation. This relationship, however, changes from the centre of the polar cap to its border. Layers are more frequent during positive By at both stations. This effect is particularly strong in the central polar cap at Thule, where a weak effect associated with Bz is also observed, with positive Bz correlating with a higher occurrence of Es. Close to the polar cap boundary, at Longyearbyen, the By effect is weaker than at Thule. On the other hand, Bz plays there an equally important role as By, with negative Bz correlating with the Es occurrence. Since Es layers can be created by electric fields at high latitudes, a possible explanation for the observations is that the layers are produced by the polar cap electric field controlled by the IMF. Using electric field estimates calculated by means of the statistical APL convection model from IMF observations, we find that the diurnal distributions of sporadic-E occurrence can generally be explained in terms of the electric field mechanism. However, other factors must be considered to explain why more layers occur during positive than during negative By and why the Bz dependence of layer occurrence in the central polar cap is different from that at the polar cap boundary.

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