scholarly journals Power Spectra of Ionospheric Scintillations

2017 ◽  
Vol 6 (4) ◽  
pp. 42-51 ◽  
Author(s):  
G. V. Jandieri ◽  
A. Ishimaru ◽  
B. Rawat ◽  
O. Kharshiladze ◽  
Z. Diasamidze
Keyword(s):  
Geomagnetic Field ◽  
Power Spectra ◽  
Orientation Angle ◽  
Density Fluctuations ◽  
Scintillation Index ◽  
Small Scale ◽  
Ionospheric Scintillations ◽  
Electron Density Fluctuations ◽  
Relationship Of ◽  
Diffraction Effects

Second order statistical moments of the phase fluctuationsare obtained taking into account the boundary condition,diffraction effects and polarization coefficients of theordinary and extraordinary waves. The variance and thecorrelation function are calculated for arbitrary 3D spectralfunction of electron density fluctuations containing bothanisotropic Gaussian and power-law spectra; anisotropycoefficient and the orientation angle of elongated plasmairregularities. The phase scintillation index and thescintillation level are analyzed numerically. Maximum ofthe scintillation index for small-scale irregularities is in theinterval 0.2-0.3 corresponding to the moderate scintillationintensity, within the weak-scatter regime. Splashes arerevealed for different anisotropy factor of elongated largescaleirregularities varying orientation angle with respect tothe lines of force of geomagnetic field. Scintillation index iscalculated for small-scale irregularities using the “frozenin”assumption and taking into account movement of rigidirregularities. Log-log plots of the power spectrum of theintensity fluctuations have the same minimums satisfyingthe “standard relationship” of scattered ordinary andextraordinary waves. It was shown that the normalizedscintillation level growth in both non-fully-developeddiffraction pattern and in transition zone increasinganisotropy factor. Rising orientation angle scintillation leveldecreases and splashes arises in fully developedscintillation region.

scholarly journals Experimental observations of medium and small scale electrostatic waves associated with ionospheric electron density fluctuations

2004 ◽  
Vol 43 (2) ◽  
pp. 173-186
Author(s):  
P. Muralikrishna ◽  
L. P. Vieira ◽  
M. A. Abdu
Keyword(s):  
Electron Density ◽  
Density Fluctuations ◽  
Small Scale ◽  
Ionospheric Electron Density ◽  
Electrostatic Waves ◽  
Electron Density Fluctuations

El 18 de diciembre, 1995 a las 21:17 hrs (TL) se colocaron a bordo de la SONDA III brasileña una prueba de Langmuir yuna de Capacitancia de Alta Frecuencia. Esta sonda fue lanzada desde la estación de lanzamiento de Alcantara (2.31°S; 44.4°W) en Brasil, para realizar mediciones de las variaciones con la altura del campo eléctrico ionosférico y de la densidad electrónica. La nave alcanzó una altitud de 557 km y cubrió un rango horizontal de 589 km. Se operaron desde tierra varios equipos para monitorear las condiciones ionosféricas durante el lanzamiento de modo que la nave alcanzara la región F, donde se presentan las burbujas de plasma. La nave alcanzó la altitud de 557 km y atravesó varias burbujas de plasma de mediano tamaño principalmente en donde se encuentra un perfil downleg de densidad. La densidad electrónica en la parte upleg del perfil mostró la presencia de una muy definida base de la región F alrededor de los 300 km, mientras que el downleg mostró la presencia de un amplio espectro de campo eléctrico e irregularidades en la densidad electrónica y el upleg de la capa F. El análisis espectral de las fluctuaciones en la densidad electrónica y el campo eléctrico indican la presencia de picos espectrales muy definidos a varias alturas que en la mayoría de los casos están asociados unos con otros. Probablemente esto indica la naturaleza electrostática de las ondas eléctricas que se excitan probablemente al inicio de la inestabilidad del plasma junto con las ondas de densidad. Se presentan algunos nuevos resultados de la asociación de estas fluctuaciones con las burbujas de plasma.

scholarly journals Diagnostics of Es Layer Scintillation Observations Using FS3/COSMIC Data: Dependence on Sampling Spatial Scale

2021 ◽  
Vol 13 (18) ◽  
pp. 3732
Author(s):  
Lung-Chih Tsai ◽  
Shin-Yi Su ◽  
Chao-Han Liu ◽  
Harald Schuh ◽  
Jens Wickert ◽  
...  
Keyword(s):  
Spatial Scale ◽  
Fresnel Zone ◽  
Signal Amplitude ◽  
Spatial Spectrum ◽  
Density Fluctuations ◽  
Wave Number ◽  
Scintillation Index ◽  
Amplitude Fluctuations ◽  
Electron Density Fluctuations ◽  
Sporadic E

The basic theory and experimental results of amplitude scintillation from GPS/GNSS radio occultation (RO) observations on sporadic E (Es) layers are reported in this study. Considering an Es layer to be not a “thin” irregularity slab on limb viewing, we characterized the corresponding electron density fluctuations as a power-law function and applied the Ryton approximation to simulate spatial spectrum of amplitude fluctuations. The scintillation index S4 and normalized signal amplitude standard deviation S2 are calculated depending on the sampling spatial scale. The theoretical results show that both S4 and S2 values become saturated when the sampling spatial scale is less than the first Fresnel zone (FFZ), and S4 and S2 values could be underestimated and approximately proportional to the logarithm of sampled spatial wave numbers up to the FFZ wave number. This was verified by experimental analyses using the 50 Hz and de-sampled FormoSat-3/Constellation Observing System for Meteorology, Ionosphere and Climate (FS3/COSMIC) GPS RO data in the cases of weak, moderate, and strong scintillations. The results show that the measured S2 and S4 values have a very high correlation coefficient of >0.97 and a ratio of ~0.5 under both complete and undersampling conditions, and complete S4 and S2 values can be derived by dividing the measured undersampling S4 and S2 values by a factor of 0.8 when using 1-Hz RO data.

SCINTILLATION EFFECTS AND THE SPATIAL POWER SPECTRUM OF SCATTERED RADIO WAVES IN THE IONOSPHERIC F REGION

2017 ◽  
Vol 13 (1) ◽  
pp. 4593-4604 ◽  
Author(s):  
George Vakhtang Jandieri ◽  
Natalia Zhukova ◽  
Zhuzhuna Diasamidze ◽  
Mzia Diasamidze
Keyword(s):  
Power Spectrum ◽  
Large Scale ◽  
Phase Fluctuation ◽  
Density Fluctuations ◽  
Magnetized Plasma ◽  
Small Scale ◽  
Radio Waves ◽  
F Region ◽  
Diffraction Effects ◽  
Spatial Power Spectrum

Differential equation for two-dimensional spectral function of the phase fluctuation is derived using the modify smooth perturbation method. Second order statistical moments of the phase fluctuations are calculated taking into account polarization coefficients of both ordinary and extraordinary waves in the turbulent collision magnetized plasma and the diffraction effects. Analytical and numerical investigations in the ionospheric F region are based on the anisotropic Gaussian and power law spectral functions of electron density fluctuations including both the field-aligned anisotropy and field-perpendicular anisotropy of the plasma irregularities. Scintillation effects in this region are investigated for the small-scale ionospheric irregularities. The large-scale background plasma structures are responsible for the double-humped shape in the spatial power spectrum taking into account diffraction effects. Numerical calculations are based on the experimental data of the navigation satellites. 

scholarly journals Polarimetric Parameters of Scattered Radiation in the Magnetized Plasma

2019 ◽  
Vol 8 (2) ◽  
pp. 77-84
Author(s):  
G. Jandieri ◽  
A. Ishimaru ◽  
J. Pistora ◽  
M. Lesnak
Keyword(s):  
Electron Density ◽  
Electromagnetic Waves ◽  
Density Fluctuations ◽  
Magnetized Plasma ◽  
Stokes Parameters ◽  
Small Scale ◽  
Plasma Slab ◽  
Smooth Perturbation ◽  
Electron Density Fluctuations ◽  
The Relationship

Second order statistical moments of scattered electromagnetic waves in the turbulent magnetized plasma slab with electron density fluctuations are calculated applying the modify stochastic smooth perturbation theory and the boundary conditions. The obtained results are valid for arbitrary correlation function of electron density fluctuations. Stokes parameters are analyzed both analytically and numerically. The theory predicts that depolarization effect caused by second Stokes parameter may be important in scintillation effects. Numerical calculations are carried out for new spectral function of electron density fluctuations containing both anisotropic Gaussian and power-law spectral functions using the experimental data. Polarimetric parameters are calculated for different anisotropy factor and inclination angle of elongated small-scale irregularities with respect to the magnetic lines of forces. The relationship between the scintillations and the polarimetric parameters is important.

scholarly journals Looking for a proxy of the ionospheric turbulence with Swarm data

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Paola De Michelis ◽  
Giuseppe Consolini ◽  
Alessio Pignalberi ◽  
Roberta Tozzi ◽  
Igino Coco ◽  
...  
Keyword(s):  
Electron Density ◽  
Geomagnetic Activity ◽  
Density Fluctuations ◽  
Rate Of Change ◽  
Topside Ionosphere ◽  
Joint Probability Distribution ◽  
Activity Levels ◽  
Scaling Exponents ◽  
Electron Density Fluctuations ◽  
Scaling Features

AbstractThe present work focuses on the analysis of the scaling features of electron density fluctuations in the mid- and high-latitude topside ionosphere under different conditions of geomagnetic activity. The aim is to understand whether it is possible to identify a proxy that may provide information on the properties of electron density fluctuations and on the possible physical mechanisms at their origin, as for instance, turbulence phenomena. So, we selected about 4 years (April 2014–February 2018) of 1 Hz electron density measurements recorded on-board ESA Swarm A satellite. Using the Auroral Electrojet (AE) index, we identified two different geomagnetic conditions: quiet (AE < 50 nT) and active (AE > 300 nT). For both datasets, we evaluated the first- and second-order scaling exponents and an intermittency coefficient associated with the electron density fluctuations. Then, the joint probability distribution between each of these quantities and the rate of change of electron density index was also evaluated. We identified two families of plasma density fluctuations characterized by different mean values of both the scaling exponents and the considered ionospheric index, suggesting that different mechanisms (instabilities/turbulent processes) can be responsible for the observed scaling features. Furthermore, a clear different localization of the two families in the magnetic latitude—magnetic local time plane is found and its dependence on geomagnetic activity levels is analyzed. These results may well have a bearing about the capability of recognizing the turbulent character of irregularities using a typical ionospheric plasma irregularity index as a proxy.

scholarly journals On the Relationship between Low Latitude Scintillation Onset and Sunset Terminator over Africa

2021 ◽  
Vol 13 (11) ◽  
pp. 2087
Author(s):  
Mogese Wassaie Mersha ◽  
Elias Lewi ◽  
Norbert Jakowski ◽  
Volker Wilken ◽  
Jens Berdermann ◽  
...  
Keyword(s):  
Moving Boundary ◽  
Occurrence Rate ◽  
Scintillation Index ◽  
Small Scale ◽  
Bahir Dar ◽  
Remarkable Change ◽  
Equatorial Africa ◽  
Night Side ◽  
Solar Terminator ◽  
First Time

The solar terminator is a moving boundary between day-side and night-side regions on the Earth, which is a substantial source of perturbations in the ionosphere. In the vicinity of the solar terminator, essential parameters like S4 index measurements are widely analyzed in order to monitor and predict perturbations in the ionosphere. The utilization of the scintillation index S4 is a well-accepted approach to describe the amplitude/intensity fluctuation of a received signal, predominantly caused by small-scale irregularities of the ionospheric plasma. We report on the longitudinal daily and seasonal occurrence of GNSS signal scintillations, using the data derived from the GNSS stations in Bahir Dar, Ethiopia, Lomé, Togo and Dakar, Senegal. The observed seasonal climatology of GNSS signal scintillations in equatorial Africa is adequately explained by the alignment of the solar terminator and local geomagnetic declination line. It should be pointed out that the strongest scintillations are most frequently observed during the time when the solar terminator is best aligned with the geomagnetic declination line. At all three stations, the comparison of computational and observational results indicated that the scintillation activity culminated around equinoxes in the years 2014, 2015 and 2016. Comparatively, the western equatorial Africa sector has the most intense, longest-lasting, and highest scintillation occurrence rate in equinoctial seasons in all three years. For the first time, we show that the seasonal variation of the scintillation peaks changes systematically from west to east at equatorial GNSS stations over Africa. A detailed analysis of the solar day–night terminator azimuth at ionospheric heights including the time equation shows that the scintillation intensity has a maximum if the azimuth of the terminator coincides with the declination line of the geomagnetic field. Due to the remarkable change of the declination by about 10° at the considered GNSS stations, the distance between scintillation peaks increases by 46 days when moving westward from the Bahir Dar to the Dakar GNSS station. The observations agree quite well with the computational results, thus confirming Tsunoda’s theory.

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