On the Relationship Between the Rate of Change of Total Electron Content Index (ROTI), Irregularity Strength (C_kL), and the Scintillation Index (S₄)

Abstract

We present a new quantitative theory for the rate of change of total electron content index (ROTI) by noting its straightforward relationship to the phase structure function of ionospheric turbulence. The theory provides the dependence of ROTI on the sampling interval, satellite motion, propagation geometry, and the spectral shape, strength, anisotropy, and drift of the irregularities. We also present useful approximations to the full theory that elucidate the principal dependencies. We show, for example, that ROTI varies with the effective scan velocity (V eff ) to the power ν − 1/2, where 2ν + 1 is the spectral index of the 3-D irregularities. This dependence on V eff persists in the ratio of ROTI to the intensity scintillation index (S 4 ), which thus depends on the particular viewing geometry for each satellite. While irregularity strength cancels when forming this ratio, the dependence on Fresnel scale remains. We validate the theory by comparing predictions of irregularity strength (C k L) and S 4 from 1-Hz ROTI measurements with calculations derived from 20-Hz intensity samples collected at Ascension Island. The theory explains the observations well, except when the scan is directed nearly along the field-aligned irregularities (within 20°of meridional). For cross-field scans the standard deviations of the error in predicting S 4 from 1-Hz ROTI were 0.05, 0.11, and 0.14 for weak, moderate, and strong scintillation, respectively. These encouraging results suggest the possibility of using dense networks of inexpensive total electron content monitors to provide quantitative diagnostics of ionospheric scintillation and the irregularities that cause them. Plain Language SummaryWe present a new theoretical model to relate a widely used statistical measure of fluctuations in total electron content to statistical measures of ionospheric irregularities and the scintillations they produce. This model includes several effects not previously accounted for quantitatively, including the sampling interval, satellite motion, propagation geometry, and the spectral shape, strength, anisotropy, and drift of magnetic field-aligned ionospheric irregularities. We validate the theory using measurements collected at Ascension Island, an equatorial station, during solar maximum conditions.

Leveraging Geodetic GPS Receivers for Ionospheric Scintillation Science

“…Correlation between SNR 4 and TEC does exists from cases of measured amplitude scintillation. The latter observation is also expected as several studies demonstrated correlation and casual relationship between ROTI and S 4 (Carrano et al, 2019;Liu & Radicella, 2019;Yang & Liu, 2016). Correlation deviation in this formalism is thought to be due to viewing geometry and irregularity drift velocity (Carrano et al, 2019;Liu & Radicella, 2019).…”

Auroral E‐Region as a Source Region for Ionospheric Scintillation

“…The high-rate measurements are not available, however, for all GPS receiver stations, and often various scintillation proxies are used that only require measurements of the total electron content (TEC) at a lower resolution, for example, at 1 Hz. One such proxy is based on the rate of TEC change index (ROTI), and although the relationship between ROTI and traditional scintillation metrics is yet to be established conclusively, some previous studies found significant correlations, particularly with S 4 at low latitudes (Carrano et al, 2019) and with σ ϕ at high latitudes (Prikryl et al, 2013). Despite wider availability…”

Analysis of the Relationship between Scintillation Parameters, Multipath and ROTI

“…Therefore, Acharya and Majumdar [33] gives the conclusion about strong evidence of a relationship between ROTI and S4, which in general agrees with the analysis from this study. In addition, Carrano et al [31] also demonstrated the theoretical relationship between ROTI and S4 and has demonstrated that this relationship is highly dependent on the sampling rate. They also provide reasons why this relationship varies between different dates and in different regions.…”

“…The relationship between ROTI and scintillation has been investigated [9,11,[31][32][33]. The scatter plot and the time series plot are common methods used in recent studies to demonstrate the linear relationship between ROTI, S4 and σ ϕ [9,11,31,32]. Additionally, the relationship between ROTI and scintillation has been shown to be affected by changes in elevation angle [11].…”

“…Investigations [9,[31][32][33] focus on S4, where σ ϕ was not investigated. Therefore, the investigation on σ ϕ is less thorough than that on S4 based on the past research [9,[31][32][33]. Though σ ϕ was investigated by Yang and Liu [11], a comparison of how both scintillation indices are related to ROTI was not undertaken.…”