Spectra of L-band ionospheric scintillation over Nanjing

Abstract

We report the spatiotemporal statistical characteristics of amplitude scintillation over Nanjing. A FFT method for computing scintillation intensity power spectra is briefly described. Using this method, the data with ISATM in Nanjing is analyzed. Spectra characteristic is presented and the irregularities property is discussed preliminarily. The results reveal that the power spectra obtained for Nanjing is consistent with theoretical modeling. At frequencies below the Fresnel frequency, the power density plotted on log-log scale is almost constant whereas above it asymptotes to a straight line. The spectral index ranges from 1.71 to 1.92, which has positive correlation with the S 4 index. Finally, the average drift velocity of irregularities is computed assumably and compared with that obtained for Xinxiang and Haikou. ionospheric scintillation, scintillation power spectra, electronic density irregularity, spectra index Citation:Fang H X, Yang S G, Wang S C. Spectra of L-band ionospheric scintillation over Nanjing. Chin Sci Bull, 2012, 57: 33753380, doi: 10.1007/s11434-012-5365-yThe ionosphere often features irregularities resulting from various unstable turbulence processes. When a radio wave from an extraterrestrial source, such as an artificial satellite, passes through the ionosphere, its wavefront will be distorted by the inhomogeneity present in the ionospheric plasma. As a result, the amplitude and phase of signals fluctuate, and the scintillation can be observed [1]. On propagating to the ground, these amplitude and phase variations cause interference to occur resulting in a diffraction pattern.Severe scintillations negatively affect trans-ionospheric radio communications and can interrupt or degrade GPS receiver operation by causing fading of the in-phase and quadrature signals, making the determination of phase by a tracking loop impossible. Degradation occurs when phase scintillations increase the frequency of cycle slips on the phase, and thus introduce ranging errors which in turn increase the dilution of precision and reduce the accuracy of GPS navigation. Since ionospheric scintillation originates from random electron density irregularities acting as wave scatterers, research on the formation and evolution of irregularities is closely related to scintillation studies [2]. A large number of theoretical investigations and statistical results have shown that the spectral analysis of scintillations from discrete radio sources and artificial satellites provides a new and valuable technique for investigating the continuous spectrum of small scale electron density irregularities in the ionosphere [3]. Information about irregularities in velocity, the equivalent thickness of the scattering layer, and irregularities in electron density can be deduced using conventional diffraction theory [4]. Also, knowledge of these irregularites is important in understanding the physical mechanisms underlying their formation and evolution; this is crucial in scintillation modeling [2]. During the past few decades, theor...

A Search for Sub-Second Radio Variability Predicted to Arise Toward 3c 84 From Intergalactic Dispersion

“…Instead, we attribute the excess power to ionospheric scintillation where the critical angular scale is 2 ′ (given by the Fresnel scale √ λd at the height of the ionosphere d ≈ 400 km). The dot-dashed curve is consistent with power spectra for ionospheric scintillation reported in the literature, for example Fang et al (2012) who present spectra with f F ≈ 0.14 Hz and power law slope ≈ −1.8 from observations of Global Positioning System satellites. Their data were obtained in 2008-2009 during solar minimum.…”

On the occurrence of F region irregularities over Haikou retrieved from COSMIC GPS radio occultation and ground‐based ionospheric scintillation monitor observations

“…The data set shows that the ionospheric scintillation has distinguished seasonal trends: it tends to occur more frequently in spring and autumn, especially in March–April and September–October, which is consistent with the previous reports [ Shi et al ., ; Xiong et al ., ; Zhou et al ., ; Huang et al ., ; Fang et al ., ; Shang et al ., ]. The tendency for ionospheric scintillation toward equinox might be due to that the magnitude of the longitudinal gradient in the integrated E region conductivity is expected to be largest during this time of year when the day‐night terminator aligns with the magnetic field, increasing the eastward electric filed and vertical upward drift as well as linear growth rate of R‐T instability, which favors the generation and evolvement of equatorial plasma bubbles (EPBs) [ Tsunoda , ].…”

“…Based on such observations, some researchers investigated the behavior of ionospheric irregularities and scintillation in the mainland of China. These studies involve the response of ionospheric irregularities to geomagnetic storms [Xu et al, 2007;Hu et al, 2013;Li et al, 2006Li et al, , 2009, the zonal drift velocities of ionospheric irregularities and its spatiotemporal variation Zhang et al, 2010;Xu et al, 2009], the morphological characteristics of ionospheric scintillation [Shang et al, 2006;Fang et al, 2012;Zhou et al, 2009;Zhang et al, 2015], its correlations with spread F, sporadic E layer (E s ), cycle slip and standard deviation of the change rate of TEC [Ning et al, 2012, Wang, 2007, Shi et al, 2014Xiong et al, 2007], and its influence on signal ranging anomaly [Huang et al, 2013].…”