L‐band scintillation activity and space‐time structure of low‐latitude UHF scintillations

Bhattacharyya, A.; Groves, K. M.; Basu, S.; Kuenzler, H.; Valladares, C. E.; Sheehan, R.

doi:10.1029/2002rs002711

Cited by 36 publications

(51 citation statements)

References 21 publications

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“…Briggs and Parkin (1963) proposed that the spectra of the electron density fluctuations along with the associated autocorrelation function obeyed generalized Gaussian statistics. However, Rufenach (1972) showed that a power law electron density fluctuation spectrum was more appropriate.…”

Section: Resultsmentioning

confidence: 99%

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Analysis of ionospheric scintillation spectra and TEC in the Chinese low latitude region

Ning

Yuan

2007

Earth Planet Sp

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GPS L-band scintillations and total electron content (TEC) were recorded at Sanya (18.33 • N, 109.52• E) during the period July 2004-July 2005. Automatic recorded raw digital scintillation data are analyzed to obtain the spectral characteristics of irregularities producing ionospheric scintillations and to estimate the correlation between amplitude scintillation and power spectral density. Concurrent measurements of TEC are used to analyze ROTI, defined as the standard deviation of the rate of change of TEC. The statistical results of S4 indices and power spectral indices indicate that the power spectral indices increase with S4 indices for weak scintillation (0.1 ≤ S4 < 0.3), but for moderate and strong scintillation, spectral indices tend to be saturated. In the analyzed data set, the ratio of ROTI/S4 is found to vary between 0.3 and 6, and the variation in estimated zonal drift velocities during geomagnetic quiet days (K p < 3) shows that the motion of the irregularities is highly variable in the initial phase of irregularity development. After about 22:00 LT, the estimated drift velocities tend to follow the same pattern.

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Section: Resultsmentioning

confidence: 99%

“…The S4 index is defined as the standard deviation of the received signal power normalized to the average signal power (Briggs and Parkin, 1963). It is calculated for each 1-min period based on a 50-Hz sampling rate (3000 data samples).…”

Section: Observations and Analytical Processmentioning

confidence: 99%

Analysis of ionospheric scintillation spectra and TEC in the Chinese low latitude region

Ning

Yuan

2007

Earth Planet Sp

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“…Every selected event represents a spectrum over 20 s or a latitudinal range of 150 km. Before determining the slope we correct for the filter effect at the high frequency end, using the function given in Equation (1). Figure 6 presents for one equator crossing in the top part a latitude profile of the ISA.…”

Section: Properties Of Signal Spectralmentioning

confidence: 99%

“…Another way to study the different scale features is provided by ground receivers monitoring the scintillation of VHF, UHF or L-band radio signals from satellites [e.g., 1,7,8]. The inherent limitation of that method is of course the confinement of observations to small regions in the ionosphere around the receivers.…”

Section: Introductionmentioning

confidence: 99%

Systematic study of intermediate-scale structures of equatorial plasma irregularities in the ionosphere based on CHAMP observations

Lühr¹,

Xiong²,

Park³

et al. 2014

Front. Physics

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Equatorial spread-F ionospheric plasma irregularities on the night-side, commonly called equatorial plasma bubbles (EPB), include electron density variations over a wide range of spatial scales. Here we focus on intermediate-scale structures ranging from 100 m to 10 km, which play an important role in the evolution of EPBs. High-resolution CHAMP magnetic field measurements sampled along north-south track at 50 Hz are interpreted in terms of diamagnetic effect for illustrating the details of electron density variations. We provide the first comprehensive study on intermediate-scale density structures associated with EPBs, covering a whole solar cycle from 2000 to 2010. The large number of detected events, almost 9000, allows us to draw a detailed picture of the plasma fine structure. The occurrence of intermediate-scale events is strongly favored by high solar flux. During times of F10.7 <100 sfu practically no events were observed. The longitudinal distribution of our events with respect to season or local time agrees well with that of the EPBs, qualifying the fine structure as a common feature, but the occurrence rates are smaller by a factor of 4 during the period 2000-2005. Largest amplitude electron density variations appear at the poleward boundaries of plasma bubbles. Above the dip-equator recorded amplitudes are small and fall commonly below our resolution. Events can generally be found at local times between 19 and 24 LT, with a peak lasting from 20 to 22 LT. The signal spectrum can be approximated by a power law. Over the frequency range 1-25 Hz we observe spectral indices between −1.4 and −2.6 with peak occurrence rates around −1.9. There is a weak dependence observed of the spectral index on local time. Toward later hours the spectrum becomes shallower. Similarly for the latitude dependence, there is a preference of shallower spectra for latitudes poleward of the ionization anomaly crest. Our data suggest that the generation of small plasma structures is part of the early stage EPB development, during times when the vertical plasma drift surpasses a certain threshold.

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“…Recently, a method has been devised for determining the spatial scales present in the ground scintillation pattern from scintillation data recorded by two spaced receivers (Bhattacharyya et al, 2003). In Sect.…”

Section: Depends On Ambient Ionospheric Conditions Present Inmentioning

confidence: 99%

Solar flux dependence of coherence scales in scintillation patterns produced by ESF irregularities

et al. 2005

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Abstract. The coherence scale length, defined as the 50% decorrelation scale length along the magnetic east-west direction, in the ground scintillation pattern obtained at a dip equatorial location, due to scattering of VHF radio waves by equatorial spread F (ESF) irregularities, is calculated, using amplitude scintillation data recorded by two spaced receivers. The average east-west drift of the ground scintillation pattern, during the pre-and post-midnight periods, also calculated from the same observations, shows an almost linear increase with 10.7-cm solar flux. In the present paper the variability of the drift is automatically taken into account in the calculation of the coherence scale length of the ground scintillation pattern. For weak scintillations, the coherence scale depends on the Fresnel scale, which varies with the height of the irregularity layer, and also on the spectral index of the irregularity power spectrum. It is found that for weak scintillations, the coherence scales are much better organized according to the 10.7-cm solar flux, during the pre-midnight period, than during the post-midnight period, with a general trend of coherence scale length increasing with 10.7-cm solar flux except for cases with F 10.7-cm solar flux <100. This indicates that, during the initial phase of ESF irregularity development, the irregularity spectrum does not have much variability while further evolution of the spatial structure in ESF irregularities is controlled by factors other than the solar flux.

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L‐band scintillation activity and space‐time structure of low‐latitude UHF scintillations

Cited by 36 publications

References 21 publications

Analysis of ionospheric scintillation spectra and TEC in the Chinese low latitude region

Analysis of ionospheric scintillation spectra and TEC in the Chinese low latitude region

Systematic study of intermediate-scale structures of equatorial plasma irregularities in the ionosphere based on CHAMP observations

Solar flux dependence of coherence scales in scintillation patterns produced by ESF irregularities

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