Problems in data treatment for ionospheric scintillation measurements

Forte, Biagio; Radicella, S. M.

doi:10.1029/2001rs002508

Cited by 117 publications

(135 citation statements)

References 10 publications

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“…However, the amplitude scintillation S 4 index remained low, a result that has been reported previously (e.g., Ngwira et al, 2010). Low S 4 index is sometimes attributed to imprecise detrending methods, which in turn may lead to overestimation of phase scintillation indices compared to amplitude scintillation indices resulting in phasewithout-amplitude scintillation (Forte and Radicella, 2002;Forte, 2005Forte, , 2007Mushini et al, 2010). Figure 3a and b shows TEC, the phase scintillation index σ φ and the ground magnetic field X-component in Taloyoak, where the magnetic local midnight and noon were at 06:37 and 19:04 UT, respectively.…”

Section: Instruments and Datamentioning

confidence: 61%

Climatology of GPS phase scintillation and HF radar backscatter for the high-latitude ionosphere under solar minimum conditions

et al. 2011

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Abstract. Maps of GPS phase scintillation at high latitudes have been constructed after the first two years of operation of the Canadian High Arctic Ionospheric Network (CHAIN) during the 2008-2009 solar minimum. CHAIN consists of ten dual-frequency receivers, configured to measure amplitude and phase scintillation from L1 GPS signals and ionospheric total electron content (TEC) from L1 and L2 GPS signals. Those ionospheric data have been mapped as a function of magnetic local time and geomagnetic latitude assuming ionospheric pierce points (IPPs) at 350 km. The mean TEC depletions are identified with the statistical high-latitude and mid-latitude troughs. Phase scintillation occurs predominantly in the nightside auroral oval and the ionospheric footprint of the cusp. The strongest phase scintillation is associated with auroral arc brightening and substorms or with perturbed cusp ionosphere. Auroral phase scintillation tends to be intermittent, localized and of short duration, while the dayside scintillation observed for individual satellites can stay continuously above a given threshold for several minutes and such scintillation patches persist over a large area of the cusp/cleft region sampled by different satellites for several hours. The seasonal variation of the phase scintillation occurrence also differs between the nightside auroral oval and the cusp. The auroral phase scintillation shows an expected semiannual oscillation with equinoctial maxima known to be associated with aurorae, while the cusp scintillation is dominated by an annual cycle maximizing in autumn-winter. These differences point to different irregularity production mechanisms: energetic electron precipitation into dynamic auroral arcs versus cusp ionospheric convection dynamics. Observations suggest anisotropy of scintillationcausing irregularities with stronger L-shell alignment of irregularities in the cusp while a significant component of Correspondence to: P. Prikryl (paul.prikryl@crc.gc.ca) field-aligned irregularities is found in the nightside auroral oval. Scintillation-causing irregularities can coexist with small-scale field-aligned irregularities resulting in HF radar backscatter. The statistical cusp and auroral oval are characterized by the occurrence of HF radar ionospheric backscatter and mean ground magnetic perturbations due to ionospheric currents.

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Section: Instruments and Datamentioning

confidence: 61%

Climatology of GPS phase scintillation and HF radar backscatter for the high-latitude ionosphere under solar minimum conditions

et al. 2011

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“…Whereas, phase scintillation is measured trough the s f parameter (Yeh & Chao-Han, 1982), which is the standard deviation of the high frequency fluctuation of the carrier phase. These fast fluctuations can be due to the diffractive effect on the carrier phase, but also to the fast movement of ionospheric irregularities, which are typical of the auroral (or polar) regions and can achieve velocities larger than 1 km/s (Forte & Radicella, 2002). In order to measure such standard deviation a previous detrending is needed which is done usually by applying a Butterworth filtering to the signal, but this filtering requires special receivers, Ionospheric Scintillation Monitoring Receivers (ISMRs), which are high level receivers that usually work with a sampling rate of 50 Hz.…”

Section: Introductionmentioning

confidence: 99%

Feasibility of precise navigation in high and low latitude regions under scintillation conditions

Zornoza

Sanz

González-Casado

et al. 2018

J. Space Weather Space Clim.

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-Scintillation is one of the most challenging problems in Global Navigation Satellite Systems (GNSS) navigation. This phenomenon appears when the radio signal passes through ionospheric irregularities. These irregularities represent rapid changes on the refraction index and, depending on their size, they can produce also diffractive effects affecting the signal amplitude and, eventually producing cycle slips. In this work, we show that the scintillation effects on the GNSS signal are quite different in low and high latitudes. For low latitude receivers, the main effects, from the point of view of precise navigation, are the increase of the carrier phase noise (measured by s f ) and the fade on the signal intensity (measured by S4) that can produce cycle slips in the GNSS signal. With several examples, we show that the detection of these cycle slips is the most challenging problem for precise navigation, in such a way that, if these cycle slips are detected, precise navigation can be achieved in these regions under scintillation conditions. For high-latitude receivers the situation differs. In this region the size of the irregularities is typically larger than the Fresnel length, so the main effects are related with the fast change on the refractive index associated to the fast movement of the irregularities (which can reach velocities up to several km/s). Consequently, the main effect on the GNSS signals is a fast fluctuation of the carrier phase (large s f ), but with a moderate fade in the amplitude (moderate S4). Therefore, as shown through several examples, fluctuations at high-latitude usually do not produce cycle slips, being the effect quite limited on the ionosphere-free combination and, in general, precise navigation can be achieved also during strong scintillation conditions.

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“…The frequency noise PSD is derived by the phase noise PSD as S Dfscint = f 2 S Duscint (Chiou et al 2007), where f represents the frequency corresponding to the ionospheric irregularity size, which is set equal to 0.19 Hz. This is a suitable value for the equatorial scintillation cases (Forte and Radicella 2002) analyzed herein. The proposed KF tracking schemes adapt their covariance matrix according to the working conditions determined by the level of detected scintillation.…”

Section: Covariance Matrix Tuning Under Scintillationmentioning

confidence: 99%

Tuning a Kalman filter carrier tracking algorithm in the presence of ionospheric scintillation

et al. 2017

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Strong ionospheric electron content gradients may lead to fast and unpredictable fluctuations in the phase and amplitude of the signals from Global Navigation Satellite Systems (GNSS). This phenomenon, known as ionospheric scintillation, is capable of deteriorating the tracking performance of a GNSS receiver, leading to increased phase and Doppler errors, cycle slips and also to complete losses of signal lock. In order to mitigate scintillation effects at receiver level, the robustness of the carrier tracking loop, the receiver weakest link under scintillation, must be enhanced. Kalman filter (KF)-based tracking algorithms are particularly suitable to cope with the variable working conditions imposed by scintillation. However, the effectiveness of this tracking approach strongly depends on the accuracy of the assumed dynamic model, which can quickly become inaccurate under randomly variable situations. This study first shows how inaccurate dynamic models can lead to a KF suboptimum solution or divergence, when both strong phase and amplitude scintillation are present. Then, to overcome this issue, it proposes two self-tuning KF-based carrier tracking algorithms, which self-tune their dynamic models by exploiting the knowledge about scintillation that can be achieved through scintillation monitoring. The algorithms have been assessed with live equatorial data affected by strong scintillation. Results show that the algorithms are able to maintain the signal lock and provide reliable scintillation indices when classical architectures and commercial ionospheric scintillation monitoring receivers fail.

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Problems in data treatment for ionospheric scintillation measurements

Cited by 117 publications

References 10 publications

Climatology of GPS phase scintillation and HF radar backscatter for the high-latitude ionosphere under solar minimum conditions

Climatology of GPS phase scintillation and HF radar backscatter for the high-latitude ionosphere under solar minimum conditions

Feasibility of precise navigation in high and low latitude regions under scintillation conditions

Tuning a Kalman filter carrier tracking algorithm in the presence of ionospheric scintillation

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