Canadian High Arctic Ionospheric Network Research Articles

The Curvature of TEC as a Proxy for Ionospheric Amplitude Scintillation

AbstractFluctuations in the ionospheric electron density cause distortions in the Global Navigation Satellite Systems (GNSS) signals recorded on the ground. The examination of these distortions reveal some of the physical conditions under which the electron density fluctuations develop as well as their physical characteristics. Several studies have investigated the correlation between the rate of change of the total electron content and amplitude and phase scintillation indices and , respectively. These studies stipulate that could be used as a proxy for scintillation indices. The link between the scintillation indices and the variations in is investigated both theoretically and empirically. Our study shows that the second derivative (the Laplacian) of the provides a better diagnosis of the nature of the interaction of trans‐ionospheric radio signals with ionospheric irregularities. In the refractive case, the second derivative of fluctuations vanishes. In the diffractive limit, we show that the amplitude scintillation index and the standard deviation of the second derivative of are linearly dependent. The theoretical results are empirically validated with measurements of GNSS radio signals propagating through the auroral ionospheric region and recorded by ground receivers of the Canadian High Arctic Ionospheric Network (CHAIN). The present study suggests that the use of as a proxy for scintillation occurring in the polar and auroral regions must be taken with caution.

Two‐Component Phase Scintillation Spectra in the Auroral Region: Observations and Model

AbstractThe random amplitude and phase fluctuations observed in trans‐ionospheric radio signals are caused by the presence of electron density irregularities in the ionosphere. Ground‐based measurements of radio wave signals provide information about the medium through which these signals propagate. The Canadian High Arctic Ionospheric Network (CHAIN) Global Position System (GPS) receivers record radio signals emitted by the GPS satellites, enabling the study of their spectral characteristics. This study presents examples of phase spectra with two power‐law components. These components exhibit steeper spectral slopes at higher frequencies and shallower ones at lower frequencies. To be more specific, we conducted a spectral characterization of sixty one (61) events recorded by the CHAIN Churchill GPS receiver, which is located in the auroral oval. When fluctuations above the background level are only observed in the phase, the spectra tend to be systematically steeper. Conversely, the power increase in higher frequency fluctuations accompanying amplitude scintillation tends to result in shallower spectra. A basic yet powerful model of radio wave propagation through a turbulent ionosphere, characterized by a power law electron density spectrum, can help to explain the two power laws observed in the scintillation events presented in this study by identifying the role played by small‐scale ionospheric irregularities in diffraction.

Spectral Characteristics of Phase Fluctuations at High Latitude

AbstractIt has long been established that ionospheric electron density irregularities cause random rapid amplitude and phase fluctuations in trans‐ionospheric radio signals. Various types of ground‐based measurements, including radar and Global Navigation Satellite System (GNSS) receivers, have been utilized to gain insights into the plasma mechanisms that could lead to the development of these ionospheric irregularities. The spectral characteristics of radio wave signals emitted by GNSSs and detected by the Canadian High Arctic Ionospheric Network Global Positioning System (GPS) receivers are analyzed to try and identify the spectral signatures of the ionospheric plasma irregularities. In the polar region, we have confirmed that phase fluctuations in the GPS signal are not always accompanied by amplitude fluctuations. For the first time, a systematic comparison is conducted on the spectral properties of phase‐fluctuation events in the absence and presence of amplitude scintillations, respectively. More specifically, a spectral characterization is performed on 41 events recorded by three receivers positioned within the auroral oval. When fluctuations above the background level are solely observed in the signal's phase, the spectrum of phase variations exhibits a consistent steepness. Conversely, the presence of amplitude scintillation is accompanied by an increase in power at higher frequencies, resulting in shallower spectra. This analysis provides yet another physical element suggesting that the rapid fluctuations observed in the signal's amplitude may be caused by Fresnel‐scale irregularities arising from a gradient‐drift‐like instability while the phase variations seem to be consistent with a refractive mechanism caused by large‐scale ionospheric structures.

Nightside High‐Latitude Phase and Amplitude Scintillation During a Substorm Using 1‐Second Scintillation Indices

AbstractWe examined evolution of Global Positioning System (GPS) scintillation during a substorm in the nightside high latitude ionosphere, using 1‐s phase and amplitude scintillation indices from the Canadian High Arctic Ionospheric Network (CHAIN) network. The traditional 1‐min scintillation indices showed that the phase scintillation was dominant, while the amplitude scintillation was weak. However, the 1‐s amplitude scintillation occurred more often in association with major auroral structures (polar cap arc, growth phase arc, onset arc, poleward expanding arc, poleward boundary intensification, and diffuse aurora) that were detected by the THEMIS all‐sky imagers (ASIs). The 1‐min index missed much of the amplitude fluctuations because they only lasted ∼10 s near a local peak or at the gradients of the auroral structures. The 1‐s phase scintillation was concurrent with the amplitude scintillation but was much weaker than the 1‐min phase scintillation. The frequency spectral analysis showed that the spectral power above ∼1 Hz was diffractive and below ∼1 Hz was refractive. We suggest that the amplitude scintillation in the high‐latitude ionosphere is much more common than previously considered, and that a short time window of the order of 1 s should be used to detect the scintillation. The 1‐min phase scintillation index is largely influenced by refractive effects due to total electron content (TEC) variations, and the spectral power below ∼1 Hz should be removed to identify diffractive scintillation.

Multi-instrument observations of polar cap patches and traveling ionospheric disturbances generated by solar wind Alfvén waves coupling to the dayside magnetosphere

Abstract. During minor to moderate geomagnetic storms, caused by corotating interaction regions (CIRs) at the leading edge of high-speed streams (HSSs), solar wind Alfvén waves modulated the magnetic reconnection at the dayside magnetopause. The Resolute Bay Incoherent Scatter Radars (RISR-C and RISR-N), measuring plasma parameters in the cusp and polar cap, observed ionospheric signatures of flux transfer events (FTEs) that resulted in the formation of polar cap patches. The patches were observed as they moved over the RISR, and the Canadian High-Arctic Ionospheric Network (CHAIN) ionosondes and GPS receivers. The coupling process modulated the ionospheric convection and the intensity of ionospheric currents, including the auroral electrojets. The horizontal equivalent ionospheric currents (EICs) are estimated from ground-based magnetometer data using an inversion technique. Pulses of ionospheric currents that are a source of Joule heating in the lower thermosphere launched atmospheric gravity waves, causing traveling ionospheric disturbances (TIDs) that propagated equatorward. The TIDs were observed in the SuperDual Auroral Radar Network (SuperDARN) high-frequency (HF) radar ground scatter and the detrended total electron content (TEC) measured by globally distributed Global Navigation Satellite System (GNSS) receivers.

Dependencies of GPS Scintillation Indices on the Ionospheric Plasma Drift and Rate of Change of TEC Around the Dawn Sector of the Polar Ionosphere

AbstractThe dependencies of global positioning system (GPS) scintillation indices on ionospheric plasma flow and the rate of change of total electron content (TEC) around the dawn sector for the first time of the polar ionosphere are investigated. The phase scintillation index (σφ) derived from GPS measurements of the Canadian High Arctic Ionospheric Network (CHAIN) shows linear dependencies on both the plasma drift speed measured by the SuperDARN radar and on the rate of change of TEC estimated from the GPS receivers of CHAIN. However, the amplitude scintillation index (S4) does not show any dependence on the plasma flow or the rate of change of TEC. These results further support Wang et al. (2018), https://doi.org/10.1002/2017JA024805 at the noon sector. The dependence of the phase scintillation index on the plasma flow further evidences that the standard phase scintillation index is dominated by refractive variations due to the use of a fixed cut‐off frequency of 0.1 Hz while detrending the phase observable. The dependence of the phase scintillation index on the rate of change of TEC consolidates the dominance of refractive variations inside.

Impact of Geomagnetic Storms on Ionosphere Variability and Precise Point Positioning Application in High Latitudes of the Northern Hemisphere

Based on the ionospheric scintillation data of the Canadian High Arctic Ionospheric Network (CHAIN), the variation characteristics of ionospheric Total Electric Content (TEC), phase scintillation and Rate of TEC Index (ROTI) were analyzed during the 26 August 2018 geomagnetic storm period. Results show that the TEC anomalies reach 20 TECU on global scale and 6 TECU over Canadian regions, respectively. The occurrence of phase scintillations is about 12.6% during the selected stormy day, which is only around 1% during geomagnetic quiet period. The occurrence of ROTI exhibits high correlation with that of phase scintillations during stormy geomagnetic conditions. The impact of ionospheric scintillations on positioning performance was analyzed by means of GPS Precise Point Positioning (PPP). It is proved that the 3D positioning root mean square errors are within 0.4 m for all test stations during the quiet geomagnetic condition. When it comes to the high geomagnetic condition, the magnitude of positioning errors significantly increase, which reaches 0.9 and 1.7 m in horizontal and vertical directions, respectively.

Temporal and spatial variations of GPS TEC and phase during auroral substorms and breakups

Temporal and spatial changes of GPS total electron content (TEC) and phase variation, called phase scintillation, during auroral substorms and breakups are investigated in the context of horizontal equivalent ionospheric currents and estimated vertical current amplitudes derived from ground magnetometer network using the spherical elementary current method. GPS phase scintillation is computed for sampling rate of 50 Hz by specialized GPS scintillation receivers from the Canadian High Arctic Ionospheric Network (CHAIN). A proxy phase scintillation index is obtained from dual frequency measurements of geodetic-quality GPS receivers sampling at 1 Hz, which include globally distributed receivers of RT-IGS network that are monitored by the Canadian Geodetic Survey in near-real-time. Based on analysis of four cases, it is shown that GPS phase scintillation maps to regions of strong westward electrojet and to the poleward edge of the eastward electrojet. For substorm onsets, auroral breakups and substorm intensifications, the ionospheric pierce points with moderate to strong phase scintillation associated with TEC enhancements map to regions of intense westward electrojet interfacing with the eastward electrojet near the boundaries between downward Region 1 and upward Region 1/Region 2 currents in the Harang discontinuity region, where intense auroral emission was observed for some of the cases studied. Energetic particle precipitation in this dynamic region results in steep electron density gradients and drifting irregularities that are the cause of GPS phase variation.

Solar Cycle Variations of GPS Amplitude Scintillation for the Polar Region

AbstractGlobal Positioning System (GPS) L1 amplitude data, obtained using the Canadian High Arctic Ionospheric Network (CHAIN) during the period 2008–2018, is used to study the seasonal and solar cycle dependence of high‐latitude amplitude scintillation. The occurrence of amplitude scintillation is predominantly confined to the 10–18 magnetic local time (MLT) and 72–87° Altitude‐Adjusted Corrected Geomagnetic (AACGM) sector and is a winter and equinoctial phenomenon. The occurrence of amplitude scintillation shows a clear seasonal and solar cycle dependence with a maximum value of ∼11% during the high solar activity early winter periods, and a secondary maximum in equinoctial months, and almost no occurrence during summer months. This pattern in occurrence suggests that amplitude scintillation is a phenomenon that is closely associated with the presence of patches and particle precipitation events.

The Limits of Empirical Electron Density Modeling: Examining the Capacity of E‐CHAIM and the IRI for Modeling Intermediate (1‐ to 30‐Day) Timescales at High Latitudes

AbstractThe Empirical Canadian High Arctic Ionospheric Model (E‐CHAIM) is a new empirical 3‐D electron density model intended as an alternative to the use of conventional standards, such as the International Reference Ionosphere (IRI), at high latitudes (above 50°N). In this study, we have manually scaled a year of data from two Canadian High Arctic Ionospheric Network (CHAIN) ionosondes. Using this high‐quality data, we examine the behavior of the polar cap ionosphere under disturbed geomagnetic conditions and assess the capacity of E‐CHAIM to model polar cap F2‐peak electron density variability on “weather‐like,” intermediate timescales (1–30 days). This is a particularly challenging environment for monthly median empirical models due to the regular occurrence of variations about the monthly mean of up to 2 MHz. We demonstrate in this study that E‐CHAIM's storm model is capable of explaining 4 to 25% of polar cap foF2 variance at 1‐ to 30‐day timescales and 5 to 50% of the amplitude of that variability, while the IRI's Storm‐Time Ionospheric Correction Model (STORM) only explains 0.2 to 9% of the variance at these timescales and no more than 5% of their amplitude. While the IRI's STORM model provided no measurable improvement over the monthly median, E‐CHAIM's storm parameterization was able to improve overall root‐mean‐square errors by 0.05 to 0.1 MHz over its quiet time model. The overall improvement through the use of storm foF2 parameterizations is found to be limited, but measurable, particularly during storm periods, where an average improvement in root‐mean‐square error of 20% is observed.

GPS TEC variations in the polar cap ionosphere: Solar wind and IMF dependence

AbstractThis statistical study examines the solar wind dependence of total electron content (TEC) variations arising from mesoscale (tens to hundreds of kilometers) structuring of the polar cap ionosphere. Six years of TEC measurements were collected from five high‐data rate Global Positioning System (GPS) receivers of the Canadian High Arctic Ionospheric Network (CHAIN), from which high‐resolution magnetic local time‐latitude maps of TEC variation occurrence rate and amplitude were created. Ionosonde radars were used to identify TEC variations arising from ionization of the E and F region ionospheres. Statistical TEC maps were examined as a function of solar wind and interplanetary magnetic field (IMF) measurements. Statistical results showed that occurrence rate of TEC variations was highest in localized dayside regions, with exact local time and latitude of peak occurrence depending primarily on the dayside coupling rate of the solar wind and magnetosphere, as well as IMF orientation and magnitude in the Y‐Z plane. Occurrence of TEC variations throughout the polar cap increased with solar wind‐magnetosphere coupling rate and IMF magnitude. The solar wind dependence of occurrence rate largely reflected the location and rate of dayside magnetic reconnection and subsequent particle precipitation and polar cap convection. Amplitudes of TEC variations were largest around noon and increased throughout the polar cap with increased solar wind‐magnetosphere coupling rate. These statistical results improve upon the existing observational picture of the polar ionosphere and will potentially facilitate development of models and techniques for mitigating impacts of the polar ionosphere on navigation signals and communication links.

Large‐amplitude GPS TEC variations associated with Pc5–6 magnetic field variations observed on the ground and at geosynchronous orbit

AbstractLarge‐amplitude variations in GPS total electron content (TEC) at Pc5–6 (<6.67 mHz) frequencies have been observed, using a high data rate Global Positioning System (GPS) receiver of the Canadian High Arctic Ionospheric Network. TEC variations with peak‐to‐peak amplitudes of 2–7 TEC units (1 TECU = 1016 el m−2) were observed over a 2.5 h period in the postnoon sector on 9 September 2011, during a period of high auroral activity within a moderate geomagnetic storm. TEC observations were from the Sanikiluaq, Nunavut (56.54°N, 280.77°E) GPS receiver located in the auroral region. Over this same time period, compressional Pc5–6 magnetic field variations were observed by the geosynchronous GOES 13 magnetometer and the ground‐based Sanikiluaq magnetometer. GOES 13 has a northern magnetic footprint in close proximity to Sanikiluaq. Cross‐correlation analysis indicates that magnetic field and TEC variations were possibly linked. No natural hazards or nuclear explosions capable of exciting TEC perturbations were reported on this day. Using a triangulation technique involving TEC measurements of multiple GPS satellites, the propagation velocity of TEC variations in the ionosphere was also calculated. This calculation revealed two distinct events: lower frequency (~0.9 mHz) TEC variations that propagated westward, consistent with the westward propagation of compressional Pc5 waves observed by GOES 13 and 15 satellites, and higher‐frequency (~3.3 mHz) TEC variations that propagated southward. This is the first report of variations in ionospheric TEC linked to satellite observations of Pc5–6 ULF waves.

Climatology of GPS phase scintillation at northern high latitudes for the period from 2008 to 2013

Abstract. Global positioning system scintillation and total electron content (TEC) data have been collected by ten specialized GPS Ionospheric Scintillation and TEC Monitors (GISTMs) of the Canadian High Arctic Ionospheric Network (CHAIN). The phase scintillation index σΦ is obtained from the phase of the L1 signal sampled at 50 Hz. Maps of phase scintillation occurrence as a function of the altitude-adjusted corrected geomagnetic (AACGM) latitude and magnetic local time (MLT) are computed for the period from 2008 to 2013. Enhanced phase scintillation is collocated with regions that are known as ionospheric signatures of the coupling between the solar wind and magnetosphere. The phase scintillation mainly occurs on the dayside in the cusp where ionospheric irregularities convect at high speed, in the nightside auroral oval where energetic particle precipitation causes field-aligned irregularities with steep electron density gradients and in the polar cap where electron density patches that are formed from a tongue of ionization. Dependences of scintillation occurrence on season, solar and geomagnetic activity, and the interplanetary magnetic field (IMF) orientation are investigated. The auroral phase scintillation shows semiannual variation with equinoctial maxima known to be associated with auroras, while in the cusp and polar cap the scintillation occurrence is highest in the autumn and winter months and lowest in summer. With rising solar and geomagnetic activity from the solar minimum to solar maximum, yearly maps of mean phase scintillation occurrence show gradual increase and expansion of enhanced scintillation regions both poleward and equatorward from the statistical auroral oval. The dependence of scintillation occurrence on the IMF orientation is dominated by increased scintillation in the cusp, expanded auroral oval and at subauroral latitudes for strongly southward IMF. In the polar cap, the IMF BY polarity controls dawn–dusk asymmetries in scintillation occurrence collocated with a tongue of ionization for southward IMF and with sun-aligned arcs for northward IMF. In investigating the shape of scintillation-causing irregularities, the distributions of scintillation occurrence as a function of "off-meridian" and "off-shell" angles that are computed for the receiver–satellite ray at the ionospheric pierce point are found to suggest predominantly field-aligned irregularities in the auroral oval and L-shell-aligned irregularities in the cusp.

A top to bottom evaluation of IRI 2007 within the polar cap

AbstractMonthly median values of ionospheric peak height (hmF2) and density (NmF2), derived from ionosonde measurements at four Canadian High Arctic Ionospheric Network (CHAIN) stations situated within the polar cap and Auroral Oval, are used to evaluate the performance of the International Reference Ionosphere (IRI) 2007 empirical ionospheric model during the recent solar minimum between 2008 and 2010. This analysis demonstrates notable differences between IRI and ionosonde NmF2 diurnal and seasonal behavior over the entire period studied, where good agreement is found during summer periods but otherwise errors in excess of 50% were prevalent, particularly during equinox periods. hmF2 is found to be marginally overestimated during winter and equinox nighttime, while also being underestimated during summer and equinox daytime by in excess of 25%. These errors are shown to be related to significant mismodeling of the M(3000)F2 propagation factor. The ionospheric bottomside thickness parameter (B0) is also evaluated using ionosonde measurements. It is found that both of the IRI's internal B0 models significantly misrepresent both seasonal and diurnal variations in bottomside thickness when compared to ionosonde observations, where errors at times exceed 40%. A comparison is also presented between IRI and Resolute (74.75N, 265.00E) Advanced Modular Incoherent Scatter Radar (AMISR)‐derived topside thickness. It is found in this comparison that the IRI is capable of modeling ionospheric topside thickness exceptionally well during winter and summer periods but fails to represent significant diurnal variability during the equinoxes and seasonal variations.

High-latitude GPS phase scintillation and cycle slips during high-speed solar wind streams and interplanetary coronal mass ejections: a superposed epoch analysis

Results of a superposed epoch (SPE) analysis of occurrence of phase scintillation and cycle slips at high latitudes keyed by arrival times of high-speed solar wind streams (HSS) and interplanetary coronal mass ejections (ICME) for years 2008 to 2012 are presented. Phase scintillation index σ Φ is obtained in real time from L1 signal recorded at the rate of 50 Hz by specialized global positioning system (GPS) ionospheric scintillation and total electron content (TEC) monitors (GISTMs) deployed as a part of the Canadian High Arctic Ionospheric Network (CHAIN). The phase scintillation, mapped as a function of magnetic latitude and magnetic local time, occurs predominantly on the dayside in the cusp and in the nightside auroral oval. The scintillation occurrence peaks on days of HSS or ICME impacts at the Earth's magnetosphere and tapers off a few days later, which is similar to day-to-day variability of geomagnetic activity and riometer absorption at high latitudes. ICMEs that are identified as magnetic clouds are significantly more geoeffective than HSSs and ICMEs with no or weak magnetic cloud characteristics. On their arrival day, magnetic clouds result in higher occurrence, and thus probability, of scintillation in the nightside auroral zone. The SPE analysis results are used to obtain cumulative probability distribution functions for the phase scintillation occurrence that can be employed in probabilistic forecast of phase scintillation at high latitudes.

Probabilistic forecasting of ionospheric scintillation and GNSS receiver signal tracking performance at high latitudes

<p>At high latitudes, phase scintillation occurs predominantly on the dayside in the ionospheric footprint of the magnetospheric cusp, and in the nightside auroral oval. A new technique of probabilistic forecasting of phase scintillation occurrence relative to the arrival time of high-speed solar wind from coronal holes and interplanetary coronal mass ejections has recently been proposed [Prikryl et al. 2012]. Cumulative probability distribution functions for the phase-scintillation occurrence that are obtained can be specified for low (below-median) and high (above-median) values of various solar wind plasma parameters. Recent advances in modeling of high-speed solar wind and coronal mass ejections, combined with the probabilistic forecasting of scintillation, will lead to improved operational space weather forecasting applications. Scintillation forecasting and mitigation techniques need to be developed to avoid potential costly failures of technology-based Global Navigation Satellite Systems in the near future, in particular during the upcoming solar maximum. The Global Navigation Satellite Systems receiver-tracking performance during severe scintillation conditions can be assessed by the analysis of receiver phase-locked-loop jitter. Tracking jitter maps [Sreeja et al. 2011] offers a potentially useful tool to provide users with expected tracking conditions, if based on scintillation predictions as proposed above. Scintillation indices are obtained from L1 GPS data collected with the Canadian High Arctic Ionospheric Network. Combined with high rate amplitude and phase data, they can be used as input to receiver tracking models to develop scintillation mitigation techniques.</p>

An interhemispheric comparison of GPS phase scintillation with auroral emission observed at the South Pole and from the DMSP satellite

<p>The global positioning system (GPS) phase scintillation caused by high-latitude ionospheric irregularities during an intense high-speed stream (HSS) of the solar wind from April 29 to May 5, 2011, was observed using arrays of GPS ionospheric scintillation and total electron content monitors in the Arctic and Antarctica. The one-minute phase-scintillation index derived from the data sampled at 50 Hz was complemented by a proxy index (delta phase rate) obtained from 1-Hz GPS data. The scintillation occurrence coincided with the aurora borealis and aurora australis observed by an all-sky imager at the South Pole, and by special sensor ultraviolet scanning imagers on board satellites of the Defense Meteorological Satellites Program. The South Pole (SP) station is approximately conjugate with two Canadian High Arctic Ionospheric Network stations on Baffin Island, Canada, which provided the opportunity to study magnetic conjugacy of scintillation with support of riometers and magnetometers. The GPS ionospheric pierce points were mapped at their actual or conjugate locations, along with the auroral emission over the South Pole, assuming an altitude of 120 km. As the aurora brightened and/or drifted across the field of view of the all-sky imager, sequences of scintillation events were observed that indicated conjugate auroras as a locator of simultaneous or delayed bipolar scintillation events. In spite of the greater scintillation intensity in the auroral oval, where phase scintillation sometimes exceeded 1 radian during the auroral break-up and substorms, the percentage occurrence of moderate scintillation was highest in the cusp. Interhemispheric comparisons of bipolar scintillation maps show that the scintillation occurrence is significantly higher in the southern cusp and polar cap.</p>

GPS phase scintillation and proxy index at high latitudes during a moderate geomagnetic storm

Abstract. The amplitude and phase scintillation indices are customarily obtained by specialised GPS Ionospheric Scintillation and TEC Monitors (GISTMs) from L1 signal recorded at the rate of 50 Hz. The scintillation indices S4 and σΦ are stored in real time from an array of high-rate scintillation receivers of the Canadian High Arctic Ionospheric Network (CHAIN). Ionospheric phase scintillation was observed at high latitudes during a moderate geomagnetic storm (Dst = −61 nT) that was caused by a moderate solar wind plasma stream compounded with the impact of two coronal mass ejections. The most intense phase scintillation (σΦ ~ 1 rad) occurred in the cusp and the polar cap where it was co-located with a strong ionospheric convection, an extended tongue of ionisation and dense polar cap patches that were observed with ionosondes and HF radars. At sub-auroral latitudes, a sub-auroral polarisation stream that was observed by mid-latitude radars was associated with weak scintillation (defined arbitrarily as σΦ < 0.5 rad). In the auroral zone, moderate scintillation coincided with auroral breakups observed by an all-sky imager, a riometer and a magnetometer in Yellowknife. To overcome the limited geographic coverage by GISTMs other GNSS data sampled at 1 Hz can be used to obtain scintillation proxy indices. In this study, a phase scintillation proxy index (delta phase rate, DPR) is obtained from 1-Hz data from CHAIN and other GPS receivers. The 50-Hz and 1-Hz phase scintillation indices are correlated. The percentage occurrences of σΦ > 0.1 rad and DPR > 2 mm s−1, both mapped as a function of magnetic latitude and magnetic local time, are very similar.

Toward the probabilistic forecasting of high‐latitude GPS phase scintillation

The phase scintillation index was obtained from L1 GPS data collected with the Canadian High Arctic Ionospheric Network (CHAIN) during years of extended solar minimum 2008–2010. Phase scintillation occurs predominantly on the dayside in the cusp and in the nightside auroral oval. We set forth a probabilistic forecast method of phase scintillation in the cusp based on the arrival time of either solar wind corotating interaction regions (CIRs) or interplanetary coronal mass ejections (ICMEs). CIRs on the leading edge of high‐speed streams (HSS) from coronal holes are known to cause recurrent geomagnetic and ionospheric disturbances that can be forecast one or several solar rotations in advance. Superposed epoch analysis of phase scintillation occurrence showed a sharp increase in scintillation occurrence just after the arrival of high‐speed solar wind and a peak associated with weak to moderate CMEs during the solar minimum. Cumulative probability distribution functions for the phase scintillation occurrence in the cusp are obtained from statistical data for days before and after CIR and ICME arrivals. The probability curves are also specified for low and high (below and above median) values of various solar wind plasma parameters. The initial results are used to demonstrate a forecasting technique on two example periods of CIRs and ICMEs.

High-latitude GPS TEC changes associated with a sudden magnetospheric compression

[1] Using ionospheric total electron content (TEC) measured by Global Positioning System (GPS) receivers of the Canadian High Arctic Ionospheric Network (CHAIN) we provide clear evidence for a systematic and propagating temporary TEC enhancement produced by compression of the magnetosphere due to a sudden increase in solar wind dynamic pressure. The magnetospheric compression is evident in THEMIS/GOES satellite data. Application of a GPS triangulation technique revealed that the TEC changes propagated with a speed of 3–6 km/s in the antisunward direction near noon and ∼8 km/s in the sunward direction in the pre-noon lower latitude sector. Characteristics of these TEC changes along with riometer absorption measurements seems to indicate that the TEC change is due to electron density enhancement in the F region and is possibly due to particle precipitation associated with sudden magnetospheric compression.