Scintillation

About: Scintillation is a research topic. Over the lifetime, 14022 publications have been published within this topic receiving 187694 citations.

Measurement and modeling of scintillation intensity to estimate turbulence parameters in an Earth-space path

Abstract: The theoretical and experimental aspects of the analysis of amplitude scintillations as a possible practical remote-sensing tool of atmospheric turbulence parameters with special emphasis on earth-space paths are explored. Theoretical studies and experimentation reveal that the scintillation variance when complemented with spectral analysis and suitable modeling of the path leads to realistic values of the parameters. A layered turbulent structure has been studied in particular, the strategy of data analysis is given in detail, and the limitations due to the cross-path wind profile are discussed.

Relationship between scintillation and rain attenuation at 19.77 GHz

Abstract: This paper reports a statistical relationship between 1-s averaged rain attenuation (A, in decibels) and standard deviation (σ, in decibels) of simultaneous tropospheric scintillation in 1-s intervals, derived from high-resolution (50 samples/s) experimental 19.77 GHz attenuation time series recorded at Spino d'Adda (45.4°N) in a 30.6° slant path to satellite Olympus during an observation time of approximately 1 year. During rain the relationship between scintillation and rain attenuation, suitably separated, can be fit by the power law σ = 0.0391A5/12 formula derivable from a turbulent-thin layer model.

Irregularity structures in the cusp/cleft and polar cap regions

Abstract: A case study of the temporal behavior of ionospheric scintillations and their frequency spectra in the cusp/cleft and polar cap regions is presented. These measurements were made at Sondrestrom and Thule, Greenland, using the 243-MHz transmissions from quasi-stationary satellites during a coupling energetic and dynamics of atmospheric regions (CEDAR) high-latitude plasma structure (HLPS)/solar terrestrial energy program (STEP) global aspects of plasma structures (GAPS) campaign. During this campaign, the incoherent scatter radar (ISR) observations were also performed at Sondrestrom, which defined the dynamic ionospheric environment in the cusp/cleft region. The availability of the radar results has enhanced this case study. It is found that scintillations at Sondrestrom are abruptly enhanced about an hour before magnetic noon when the propagation path to the satellite entered the cusp/cleft region. Subsequently, a series of enhanced and reduced scintillation activity was detected. The enhanced scintillation structures were found to be asymmetric, with sharp leading edges and diffuse trailing edges. Spaced-antenna scintillation measurements at Sondrestrom detected considerable velocity shear, and the frequency spectra showed flat low-frequency portions, implying the presence of turbulent plasma flows. A comparison with the ISR observations indicates that the temporal variation of scintillation was caused by the poleward convection of alternate regions with high- and low-ionization density, the density depletions being caused by channels of high zonal flows associated with velocity shear. The level of scintillation observed in the low-density regions imply the presence of small-scale irregularities with considerable irregularity amplitude. In contrast to the above behavior, the polar cap scintillations exhibit deep minima between the transit of successive “patches” of ionization, and their frequency spectra imply the absence of turbulent plasma flows. It is postulated that in the cusp/cleft and polar cap regions, the gradient-drift instability mechanism generates the observed small-scale irregularities associated with discrete density enhancements, whereas a shear-driven instability, such as the nonlinear collisional Kelvin-Helmholtz (K-H) instability mechanism, may generate the irregularities in the intervening low-density regions.

Characteristics of deep gps signal fading due to ionospheric scintillation for aviation receiver design

Abstract: [1] Deep and frequent fading of Global Positioning System (GPS) signals caused by ionospheric scintillation is a major concern for aircraft navigation using GPS in the equatorial region during solar maximum. Aviation receivers use both code and carrier measurements to calculate position solutions. Deep signal fading can break a receiver's carrier tracking lock to a satellite channel. The lost channel cannot be used for position calculation until the receiver reacquires the channel and reestablishes tracking. A solar maximum data set analyzed in this paper demonstrates frequent deep signal fading of almost all satellites in view. This could significantly reduce the number of simultaneous tracked satellites and consequently decrease navigation availability. Forty-five minutes of strong scintillation, which was the worst scintillation period of a 9 day campaign at Ascension Island in 2001, are analyzed in this paper. The importance of short reacquisition time of the receiver is described. In order to design an aviation receiver with short reacquisition time under frequent deep signal fading, the characteristics of signal fading should be well understood. Fading duration and the time between deep fades are two important characteristics for GPS navigation. This paper presents a fading duration model based on real scintillation data. The time between deep fades observed in this data shows very frequent deep fades which can significantly reduce benefit of carrier smoothing filters of aviation receivers.