Rankin Inlet Research Articles

Climate change and sea ice: Shipping in Hudson Bay, Hudson Strait, and Foxe Basin (1980–2016)

The seasonally ice-covered waters of Hudson Bay, James Bay, Foxe Basin, and Hudson Strait (“the study area”) are bordered by 39 communities with a total population of roughly 50,000 people, most of whom are Inuit or Cree. Sea ice is a cornerstone of the environment and culture of the study area but is also the main barrier to shipping traffic, which has been growing in the area. This paper presents a review of sea ice and shipping in the study area and an analysis of shipping accessibility as represented by the timing of breakup, freeze-up, and the open water season in its offshore and local waters. Offshore ice timing was analyzed using passive microwave-based data for 1980–2014; local ice timing near Rankin Inlet, Churchill, Kuujjuarapik/Whapmagoostui, and Salluit was examined using Canadian Ice Service ice charts for 1996–2016. Open water was defined using sea ice concentration thresholds of ≤15% (offshore) or <20% (local) in an attempt to represent accessible conditions for open water shipping vessels. The results for both offshore and local waters display considerable spatial variability. For offshore waters, breakup currently occurs between 17 May and 19 August and freeze-up occurs between 22 October and 30 December, with overall trends (1980–2014) of +0.58 days year–1 towards an earlier breakup, +0.47 days year–1 towards a later freeze-up, and +0.97 days year–1 towards a longer open water season. Also, significant relationships amongst breakup and freeze-up were observed. For local waters, the 1996–2016 average open water season at the four communities varied between 112.7 days (Churchill) and 154.7 days (Kuujjuarapik/Whapmagoostui). Ultimately, shipping accessibility to Rankin Inlet, Churchill, and Salluit appears to be limited by their local ice timing, while accessibility to Kuujjuarapik/Whapmagoostui appears to be limited by ice timing in northeastern Hudson Bay.

Radar observations of density gradients, electric fields, and plasma irregularities near polar cap patches in the context of the gradient‐drift instability

AbstractWe present observations of plasma density gradients, electric fields, and small‐scale plasma irregularities near a polar cap patch made by the Super Dual Auroral Radar Network radar at Rankin Inlet (RKN) and the northern face of Resolute Bay Incoherent Scatter Radar (RISR‐N). RKN echo power and occurrence are analyzed in the context of gradient‐drift instability (GDI) theory, with a particular focus on the previously uninvestigated 2‐D dependencies on wave propagation, electric field, and gradient vectors, with the latter two quantities evaluated directly from RISR‐N measurements. It is shown that higher gradient and electric field components along the wave vector generally lead to the higher observed echo occurrence, which is consistent with the expected higher GDI growth rate, but the relationship with echo power is far less straightforward. The RKN echo power increases monotonically as the predicted linear growth rate approaches zero from negative values but does not continue this trend into positive growth rate values, in contrast with GDI predictions. The observed greater consistency of echo occurrence with GDI predictions suggests that GDI operating in the linear regime can control basic plasma structuring, but measured echo strength may be affected by other processes and factors, such as multistep or nonlinear processes or a shear‐driven instability.

On the consistency of the SuperDARN radar velocity and E × B plasma drift

AbstractJoint observations of the Rankin Inlet (RKN) and Inuvik Super Dual Auroral Radar Network (SuperDARN) HF radars and Resolute Bay incoherent scatter radar (RISR) are used to assess consistency in their plasma flow velocity measurements. The analysis covers more than 500 h of successful concurrent measurements. We demonstrate that, overall, the radars show close velocities, although there were minor differences including SuperDARN velocity underestimation, in line with previous publications, and the persistent occurrence of measurements with a SuperDARN velocity magnitude above the RISR velocity magnitude. We argue that, for one event, the velocity overestimation occurs owing to echo detection from a laterally refracted RKN beam while, generally, the effect should be fairly wide‐spread in SuperDARN data because of microstructures with enhanced electron density in the scattering volume that might have either weak irregularities or increased local electric fields. We estimate that the correction of RKN velocity data by considering the effect of the index of refraction improves RKN‐RISR velocity agreement but only for 63% of points. This implies that care should be exercised when attempting to correct raw SuperDARN velocity data by the index of refraction.

Rapid Nestling Mortality in Arctic Peregrine Falcons due to the Biting Effects of Black Flies

This note describes nestling mortality in Arctic Peregrine Falcons (Falco peregrinus tundrius) due to the biting effects of blood-feeding black flies (Diptera: Simuliidae). At a nest site near Rankin Inlet, Nunavut, Canada (62˚49′ N, 92˚05′ W), a brood of four nestlings died on 20 July 2013 from the direct effects of severe bites attributed to black flies. Within three hours of the onset of blood-feeding, black flies had caused widespread, uniformly distributed hemorrhagic coalescent lesions over the head and body of all nestlings. Approximately seven hours after the first flies appeared, the female falcon removed the carcasses of the dead nestlings from the nest. Nestlings at eight additional sites also suffered the effects of biting black flies in 2013, resulting in the deaths of 13 of 35 nestlings. A less pronounced outbreak also occurred in 2012 and resulted in the deaths of seven nestlings at four sites. No nestling mortality due to black flies has been documented in any other year from 1982 through 2015. To our knowledge, these observations document the northernmost lethal attack by ornithophilic black flies in North America.

Age and geological setting of the Rankin Inlet greenstone belt and its relationship to the gold endowment of the Meliadine gold district, Nunavut, Canada

Archean greenstone belts host a significant proportion of the world's gold, typically in deposits that formed late during greenstone belt formation and cratonization. However, this is not always the case and, in the multiply reworked western Churchill Province (wCP), orogenic lode gold deposition post-dates greenstone belt formation by nearly one billion years. The spatial link between Proterozoic gold and Archean greenstone belts in the wCP is thus particularly striking although its significance is still not fully understood. The Meliadine gold district (2.8Moz contained Au in reserves, plus an indicated and inferred resources of 5.8Moz Au) represents an important example of this deposit style and is hosted within the Rankin Inlet greenstone belt (RIGB), which occupies a critical, but controversial position along the largely inferred boundary between the Hearne craton and the Chesterfield block.RIGB felsic volcanic rocks (ca. 2.66Ga) are structurally intercalated, and broadly coeval, with mafic volcanic and volcaniclastic rocks (2.66–2.64Ga), turbidite (≤2.66–2.64Ga), argillite, auriferous banded iron formation successions and syn-volcanic granodioritic to tonalitic intrusions (2.67–2.64Ga). Neoarchean basaltic to andesitic volcanic rocks possess calc-alkaline to primitive arc-like tholeiitic magmatic affinities along with lesser MORB-like basaltic compositions. Geochemically evolved lavas yield depleted 144Nd/143Nd ratios (ɛNd2.66Ga=−1.1 to +1.6) that reflect variable interaction with an evolved and hitherto undocumented Meso- to Neoarchean basement underlying the RIGB, whereas transitional, arc-like primitive tholeiitic and MORB-like basaltic samples overlap with the Nd isotopic composition of depleted mantle at ca. 2.66Ga (ɛNd2.66Ga=+1.6 to +2.7). These Neoarchean volcano-sedimentary panels represent the main auriferous rock package within the Meliadine gold district and are intercalated with deformed Paleoproterozoic conglomerate (≤2.50 and ≤2.155Ga). The latter are, in turn, unconformably overlain by a geochemically distinct pillowed-basalt sequence and a unique carbonate-siliciclastic package that presumably represent the remnants of Paleoproterozoic basins and are not known to host gold. The geological setting of gold deposits thus likely reflects this favourable Neoarchean lithostratigraphy in addition to metamorphism and fluid focusing along the reactivated faults during the collision of the Hearne and combined Chesterfield block-Rae craton at 1.90–1.85Ga.

Unraveling the Western Churchill Province Paleoproterozoic Gold Metallotect: Constraints from Re-Os Arsenopyrite and U-Pb Xenotime Geochronology and LA-ICP-MS Arsenopyrite Trace Element Chemistry at the BIF-Hosted Meliadine Gold District, Nunavut, Canada

The gold endowment of the western Churchill Province is conventionally attributed to reworking and attendant metamorphism during the Trans-Hudson Orogeny (1.9–1.8 Ga). The Meliadine gold district is regarded as a type example of this inferred Paleoproterozoic gold metallotect and also represents one of Canada’s largest emerging orogenic greenstone- and banded iron formation (BIF)-hosted gold districts (2.8 Moz contained Au in reserves and total resource of 5.8 Moz Au). The largest gold deposits are cospatial with the Pyke fault and associated quartz (± ankerite) veining, which cuts Neoarchean (ca. 2.66 Ga) plutonic and supracrustal rocks comprising the Rankin Inlet greenstone belt. Meliadine gold occurs as inclusions within idioblastic arsenopyrite crystals, at sulfide crystal boundaries, and/or as sulfide fracture fills in hydrothermally altered, sulfidized, and veined BIF. Clusters of gold, Bi-Mo telluride, chalcopyrite, and galena inclusions characterize high-grade ore zones and are spatially associated with sieve-textured arsenopyrite domains. These microtextural relationships suggest that incipient sulfide recrystallization liberated gold, which, along with other precious and base metals, was redistributed during late, fluid-assisted and deformation/metamorphic-driven remobilization. Late precious and base metal enrichment is also demonstrated by in situ laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) arsenopyrite mapping. Hydrothermal xenotime crystals occur with gold in low-strain microtextural sites and yield U-Pb ages at ca. 1.86 Ga, suggesting that remobilization was concomitant with Trans Hudson orogenesis. New Re-Os arsenopyrite model ages range from 2.3 to 1.8 Ga and document a hitherto unrecognized, pre-1.86 Ga hydrothermal activity. The range of Re-Os model ages tends to support partial open-system behavior and/or mixing of disparate arsenopyrite generations that are evident from microtextural observations and in situ LA-ICP-MS element mapping. Replicate analyses of the two most rhenium rich arsenopyrite samples yield reproducible Re-Os model ages at ca. 2.27 and 1.90 Ga. These rhenium-rich samples are also gold poor and likely yield ages that predate gold remobilization and subsequent enrichment along arsenopyrite crystal boundaries and fractures. We suggest that pre-1.86 Ga hydrothermal activity was likely critical to the gold endowment of the district, but is obscured by reworking during the later stages of the Trans-Hudson Orogeny at 1.86 Ga. If correct, these new ages imply that the Paleoproterozoic gold metallotect, which is recorded across the western Churchill Province, in fact comprises multiple, temporally distinct gold events. Differentiating between disparate Paleoproterozoic gold events represents a critical step for effective mineral exploration in the western Churchill Province and at other reworked Archean terranes.

Electron density and electric field over Resolute Bay andFregion ionospheric echo detection with the Rankin Inlet and Inuvik SuperDARN radars

Joint observations of the Rankin Inlet and Inuvik Super Dual Auroral Radar Network HF radars and Resolute Bay (RB) Canadian Advanced Digital Ionosonde are used to assess the electron density at the F region peak and the electric field magnitude as factors affecting echo detection over RB. We demonstrate that the radars show similar diurnal and seasonal variations in ionospheric echo occurrence. During nighttime and at radar frequencies of ~12 MHz, optimum densities for both radars are shown to be ∼ 1.4 × 105 cm− 3, ~1.8 × 105 cm− 3, and ~2.0 × 105 cm− 3 for winter, equinox, and summer, respectively. During daytime, optimum densities are larger by (0.2 − 0.3) × 105 cm− 3. Observations at lower radar frequencies of ~10 MHz show smaller required densities during nighttime, by ~0.3 × 105 cm− 3. Optimum electric fields for the moments of echo detection over RB are found to be 5–25 mV/m with no clear threshold effect and any seasonal dependence. The presented data suggest that for echo detection, favorable propagation conditions along the entire path of radio waves toward the scattering volume are important.

Seasonal and diurnal variations of PolarDARN F region echo occurrence in the polar cap and their causes

AbstractF region echo occurrence rates for the Polar Dual Auroral Radar Network (PolarDARN) HF radars at Inuvik (INV), Rankin Inlet (RKN), and Clyde River (CLY) are compared for observations in 2013. The CLY radar shows somewhat smaller echo occurrence rates consistent with its more poleward geographic and geomagnetic location. For all three radars, the winter occurrence rates are roughly twice that of the corresponding summer rates. For observations in the midnight sector, strong equinoctial maxima are evident. In terms of season and local time, echo occurrence patterns are found to be roughly the same for all radars: seasonally, clear maxima are found near noon during both winter and summer, while, diurnally, enhancements are found during equinoctial dusk. A comparison of data from roughly the same scattering area shows that having strong electron density in the scattering volume is not sufficient for getting an HF echo: propagation conditions along the propagation path are also important. Diurnal variations in the F region electron density and electric field (both measured by Canadian Advanced Digital Ionosonde) are compared to those of RKN echo occurrence rates for observations over Resolute Bay (RB) located at a geomagnetic latitude of 83°N. These results show a reasonable correlation between occurrence and electron density for both winter and summer periods and correlation between occurrence and electric field during summer periods.

On the increasing oscillation period of flows at the tailward retreating flux pileup region during dipolarization

AbstractOn 23 March 2009 between 6:00 and 6:40 UT, three Time History of Events and Macroscale Interactions during Substorms probes (P3, P4, and P5) were at about −11.5 Earth radii (RE) and two (P1 and P2) were at −14 RE downtail. The inner probes (P3–P5) started to observe oscillatory flow braking with plasma sheet dipolarization due to flux pileup at about 6:04 UT. After 6:16 UT the flux pileup region (FPR) expanded tailward as the outer probes (P1 and P2) moved closer to the neutral sheet and began to observe oscillatory braking also. During the FPR tailward expansion, the flow oscillation period increased from about 3.5 min at P3–P5 to about 6.2 min at P1 and P2. Meanwhile, as observed by the all‐sky camera at Rankin Inlet, auroral activity gradually moved northward indicating that the characteristics of oscillatory flows at the tailward retreating FPR may be crucial for understanding the magnetosphere‐ionosphere coupling.

“That’s where our future came from”: Mining, landscape, and memory in Rankin Inlet, Nunavut

Based on ethnographic and oral history research, this article investigates community experiences of historical and contemporary mineral development in the Arctic through an analysis of the cultural landscape of Rankin Inlet, Nunavut. The town was established in the 1950s around the North Rankin Nickel Mine—Arctic Canada’s first industrial mining operation. The mine’s rapid closure in 1962 dealt a devastating blow to the local economy, with about half the community staying in Rankin Inlet and struggling to make a living. In spite of the long period since closure, the mine’s influence is still present in the town’s built environment and cultural landscapes. Our research seeks to reveal the symbolic attachments both Inuit and long-term Qallunaat residents have formed with the post-industrial landscape. We argue that Rankin Inlet, as a community, is coming to terms with and (re)staking its claims to its industrial past, as part of contemporary efforts to manage the costs and benefits of new mineral development in the region.

State, company, and community relations at the Polaris mine (Nunavut)

Inuit employment in the mining industry has received very little attention from historians, although mining has been in the Arctic since the 1950s. Using the Polaris mine (1982-2002) on Little Cornwallis Island, Nunavut, as a case study, this article focuses on the Canadian government’s shift away from supporting mining developments in the late 1970s to early 1980s, on Inuit employment in the mining industry, and on the difficulties of Inuit from Resolute Bay in obtaining employment at Polaris. Previous to Polaris, the federal government saw Arctic mines, particularly Rankin Inlet (1951-1962) and Nanisivik (1976-2002), as a path to modernisation for the Inuit. However, as these earlier Arctic mines failed in this particular goal, the State became disillusioned and weary of providing financial support by the time Cominco began planning the Polaris mine in 1973. The federal government did not require Cominco to sign a formal agreement for Inuit employment, leaving the company responsible to develop its own hiring agenda. Unfortunately for the people of Resolute Bay, the company agenda did not include hiring locals as a priority, and bypassed and marginalised Resolute Bay Inuit who were keen on working at the mine. As mining has been the largest industry in the Canadian northern economy and is currently growing and beginning new development projects, it is important to understand the historical dynamics between mining companies, the State, and local communities.

Wistful thinking: Making Inuit labour and the Nanisivik mine near Ikpiarjuk (Arctic Bay), northern Baffin Island

This article interrogates discourse about Inuit in relation to employment issues and the Inuit response to “what was good for them” at the intersection of colonial and postcolonial thought in the 1970s. Attempts to integrate Inuit with a modern industrial economy occurred after Inuit had moved, or been moved, from land-based hunting and trapping camps to new settlements developing in the eastern Arctic. We examine the planning stage (1970-1976) of the Nanisivik mine at Strathcona Sound on the northern tip of Baffin Island that operated from 1976 until 2002. Building on the work of James O’Connor in the early 1970s and concepts of legitimisation and accumulation functions of the State, and using the archival records of the Department of Indian Affairs and Northern Development and the Department of Energy, Mines, and Resources, we explore the extent to which Inuit were constructed as “labour in need of employment.” In examining debate between officials of these departments, we seek to find out to what extent other needs went unmet, based on experience with the Rankin Inlet Nickel Mine (1957-1962). Inuit resistance to this definition and the relationship between Inuit as hunters and Inuit as wage earners are explored with reference to contemporary mining development in Nunavut.

1.8 billion years of fluid–crust interaction: A zircon oxygen isotope record for the lower crust, western Churchill Province, Canadian Shield

The western Churchill Province of the Canadian Shield experienced a prolonged and complex formation history (ca. 4.04 to 1.70Ga), with evidence for multiple episodes of orogenesis and regional magmatic activity. Here we report on the oxygen isotopic compositions of garnet and zircon recovered from lower crustal xenoliths, which have U–Pb ages between ca. 3.5 and 1.7Ga. Overall, zircon from four metabasite xenoliths from the Rankin Inlet sample suite have δ18O values ranging from +5.5 to +8.6‰. Zircon from three metatonalite/anorthosite xenoliths and five metabasite xenoliths from the Repulse Bay sample suite have δ18O values of +5.6 to +8.3‰. High δ18O values (>+6.0‰) for the oldest igneous zircon cores (ca. 3.5Ga and 3.0–2.6Ga) indicate that their metatonalite/anorthosite protolith magmas were generated from, or had assimilated, supracrustal rocks that interacted previously with surface-derived fluids. Igneous zircon cores (ca. 2.9–2.6Ga) from one metabasite xenolith have δ18O values of +5.6 to +6.4‰, which suggests a formation from a mantle-derived basaltic/gabbroic magma. Metamorphic zircon cores (ca. 2.0–1.9Ga) from one metabasite xenolith commonly have δ18O values between +6.0 and +6.3‰, which is indicative of a basalt/gabbro protolith and localized reworking of the lower crust caused by regional-scale plate convergence. The wide range of δ18O values (+5.5 to +8.3‰) for ca. 1.75–1.70Ga metamorphic zircon rims (identified in all xenoliths) indicates regional transient heating and reworking of mantle- and supracrustal-derived crust, induced by magmatic underplating along the crust–mantle boundary.

Statistical relationships between enhanced polar cap flows and PBIs

AbstractPoleward boundary intensifications (PBIs) are auroral intensifications along the poleward boundary of the auroral oval and occur during all levels of geomagnetic activity. However, little is known about the triggering of PBIs. Recent case studies have indicated the existence of longitudinally localized flow channels in the polar cap near, and directed toward, the nightside open‐closed field line boundary just before PBIs. Motivated by these studies, we analyze 115 events of coordinated observations by the Time History of Events and Macroscale Interactions during Substorms all‐sky imager and Super Dual Auroral Radar Network HF radar at Rankin Inlet to determine if this polar cap flow‐PBI relationship is commonly observed. We start with isolated and intense PBIs and examine the probability of them being associated with equatorward directed polar cap flows. Our results show the association to be frequent (90%), with one‐to‐one correlations occurring in ~50% of events. Considering the limitations of the radar observations, this result indicates that PBIs are commonly correlated with polar cap flow channels directed toward, and then traversing, the open‐closed field line boundary. The flows statistically occur ~1–2 min before the PBI initiations, and the duration and width of the flows are comparable to those of the PBIs. We also perform a reverse study by starting with isolated polar cap flows and obtain similar results. The remarkably high occurrence of association between enhanced polar cap flows and PBIs indicates that enhanced mesoscale flows within the open field line region that traverse the open‐closed field line boundary are an important driver of PBI formation.

Age and evolution of the lower crust beneath the western Churchill Province: U–Pb zircon geochronology of kimberlite-hosted granulite xenoliths, Nunavut, Canada

Zircon from granulite-facies xenoliths can preserve unique geodynamic records of deep and mostly inaccessible levels of the continental crust within Archean cratons. We present the first such records from beneath two Archean crustal blocks that were affected by multiple episodes of regional-scale Proterozoic metamorphism, and are located within the western Churchill Province, Nunavut, Canada. Zircon U–Pb geochronology and trace element analysis were carried out on samples that originated in the deep crust at the time of kimberlite eruption, as confirmed with Raman spectroscopy. Zircon was recovered from four metabasites (grt–cpx–plg) from the Rankin Inlet area of the Chesterfield block, and five metabasites (grt–cpx–plg±hbl±opx) and three metatonalite/anorthosites (plg–cpx–plg±hbl±opx) from the Repulse Bay area of the Rae craton. SEM-CL imaging reveals several types of growth zoning diagnostic of igneous and metamorphic zircon crystallization. The latter are related to local high-temperature recrystallization and micro-fracturing, and are spatially associated with zones of apparent Pb-loss and/or intracrystalline Pb-variability. Evidence for the formation of Paleoarchean/Mesoarchean to Neoarchean crust is preserved in oscillatory zoned, igneous cores having 207Pb/206Pb ages of ca. 3.5Ga and ca. 3.0–2.6Ga. Two periods of Paleoproterozoic metamorphism and zircon growth followed, with the oldest episode at ca. 2.0–1.9Ga in the Chesterfield block. Metamorphic zircon rims from all twelve xenoliths have an age range of ca. 1.75 to 1.70Ga. The trace element compositions of the metamorphic rims differ from those of older igneous and metamorphic cores, with the rims characterized by lower ΣHREE contents and low (Lu/Gd)N, suggesting that garnet crystallization occurred syn- to pre-rim growth at ca. 1.75Ga. The Archean and Paleoproterozoic ages correspond broadly to the upper crustal histories of the western Churchill Province; however, the prevalence of ca. 1.75–1.70Ga metamorphic rims indicates regional-scale metamorphic reworking of the lower crust across the region, during a period of intracratonic extension and associated magmatism. Regional magmatic underplating and/or remobilization of the lithosphere at ca. 1.75–1.70Ga, to an extent not widely appreciated, represents a terminal stage in western Churchill cratonization, including stabilization of reworked Archean crust relative to underlying diamondiferous mantle.

Landscape heterogeneity drives intra-population niche variation and reproduction in an arctic top predator.

While intra-population variability in resource use is ubiquitous, little is known of how this measure of niche diversity varies in space and its role in population dynamics. Here we examined how heterogeneous breeding environments can structure intra-population niche variation in both resource use and reproductive output. We investigated intra-population niche variation in the Arctic tundra ecosystem, studying peregrine falcon (Falco peregrinus tundrius, White) breeding within a terrestrial-marine gradient near Rankin Inlet, Nunavut, Canada. Using stable isotope analysis, we found that intra-population niches varied at the individual level; we examined within-nest and among-nest variation, though only the latter varied along the terrestrial-marine gradient (i.e., increased among-nest variability among birds nesting within the marine environment, indicating higher degree of specialization). Terrestrial prey species (small herbivores and insectivores) were consumed by virtually all falcons. Falcons nesting within the marine environment made use of marine prey (sea birds), but depended heavily on terrestrial prey (up to 90% of the diet). Using 28-years of peregrine falcon nesting data, we found a positive relationship between the proportion of terrestrial habitat surrounding nest sites and annual nestling production, but no relationship with the likelihood of successfully rearing at least one nestling reaching 25 days old. Annually, successful inland breeders raised 0.47 more young on average compared to offshore breeders, which yields potential fitness consequences for this long-living species. The analyses of niche and reproductive success suggest a potential breeding cost for accessing distant terrestrial prey, perhaps due to additional traveling costs, for those individuals with marine nest site locations. Our study indicates how landscape heterogeneity can generate proximate (niche variation) and ultimate (reproduction) consequences on a population of generalist predator. We also show that within-individual and among-individual variation are not mutually exclusive, but can simultaneously arise and structure intra-population niche variation.

Comparison of SuperDARN irregularity drift measurements and F-region ion velocities from the resolute bay ISR

A number of studies have addressed the principal assumption used by the SuperDARN network of HF radars that the scatter from F region field-aligned irregularities has a Doppler shift given by the cosine component of the EXB plasma drift. However, the slopes of the best-fit line to the measured points have consistently been low, perhaps implying contamination from irregularities with smaller amplitude drifts. This work is motivated by testing the same assumption on a more optimal experimental setting: using the north face of the Resolute Bay incoherent scatter radar (RISR-N), which provides high resolution magnitude and direction measurements of EXB drift in a region where the ionospheric flow is mostly uniform relative to auroral latitudes, thereby reducing echo mixing due to spatio-temporal structuring. We compared the EXB drift measured by RISR-N to the line-of-sight Doppler velocities measured PolarDARN which is composed of Rankin Inlet and Inuvik HF radars, both having a field of view over Resolute Bay. An aggregate scatter plot of all the echoes observed during a 5-day period in early May 2011 contains two distinct groups of echoes. The first group is hypothesized to be from the E region because the echoes appear above a threshold EXB drift and at small flow angles, which are characteristics of primary Farley–Buneman waves. The Doppler velocity of the second group of echoes increase linearly with the EXB drift and is identified here as F region echoes. A special joint fit showed a slope of 0.85 for the F region echoes. During the observation period, the F region electron density has large variations between 1 and 10×1011, in particular due to the polar cap patches. Considering a representative F region electron density of 5×1011 m−3, which has a refraction index of 0.86 at 12.5MHz (for PolarDARN frequencies) and the fact that the measured velocity is the product of the actual velocity and the refractive index, the expected slope is 0.86, in agreement with our measurement. The fit for E region Doppler velocities shows a saturation speed at 170m/s, while the data were spread between 100 and 300m/s. Although the saturation speed is somewhat lower than the ion acoustic speed, it is acceptable considering earlier work attributing similarly low velocities to large aspect angles at the scattering altitudes.

Assessing Doppler velocities of Rankin Inlet F-region echoes

Doppler velocities observed by the Rankin Inlet (RKN) PolarDARN radar are assessed with a focus on data in thebeams oriented roughly along the magnetic meridian. Hourly scatter plots for every month are built. They are shown to varywidely, with median values showing very clear magnetic local time variation with maximum magnitude during pre-noon andpre-midnight hours. The histograms contain a significant amount of very small velocity data that dominates at farther ranges andduring the daytime. Near noon data show generally antisunward flows but at large ranges/magnetic latitudes and very close tonoon, sunward flows occur for periods of positive IMF B z . The reverse flows are stronger during spring equinox. The velocity magnitudewas found to depend linearly on the IMF B z and interplanetary electric field. Velocities are often found to be smaller thanthose expected from the statistical convection model of Ruohoniemi and Greenwald –1996.

Resolute Bay CADI ionosonde drifts, PolarDARN HF velocities, and cross polar cap potential

In this study, velocities measured by the Rankin Inlet and Inuvik PolarDARN HF radars over Resolute Bay (RB) are compared with measurements from the RB CADI ionosonde to investigate the consistency of the measurements. Two types of comparisons are performed: 1‐D, where each PolarDARN radar line‐of‐sight velocity is plotted against CADI velocity projected onto appropriate radar beam, and 2‐D, where the PolarDARN merged velocity is compared with the full CADI vector. In both cases, velocities were found to statistically agree. For the 1‐D comparison, the velocities were comparable in ∼85% of cases. For the 2‐D comparison, a minor tendency for larger PolarDARN merge velocities (∼60 m/s) was noticed. The second task performed is a comparison of the SuperDARN cross polar cap potential (CPCP) and the CADI‐based CPCP and their dependence on the CADI velocity. Linear dependences were found allowing for inter‐conversion between these parameters. For large plasma drifts, the SuperDARN CPCPs were found to be much smaller than the CADI‐based CPCPs hinting that the separation between the foci of a large‐scale convection pattern is often underestimated in the SuperDARN convection mapping.

Signatures of moving polar cap arcs in the F-region PolarDARN echoes

Abstract. Joint observations of the all-sky camera at Resolute Bay (Nunavut, Canada) and the Polar Dual Auroral Radar Network (PolarDARN) HF radars at Rankin Inlet and Inuvik (Canada) are considered to establish radar signatures of poleward moving polar cap arcs "detaching" from the auroral oval. Common features of the events considered are enhanced power or echo occurrence in the wake of the arcs and enhanced spectral width of these echoes. When the arcs were oriented along some of the radar beams, velocity reversals at the arc location were observed with the directions of the arc-associated flows corresponding to a converging electric field. For the event of 9 December 2007, two arcs were poleward progressing almost along the central beams of the Inuvik radar at the speed close to the E × B drift of the bulk of the F-region plasma as inferred from HF Doppler velocities and from independent measurements by the Resolute Bay ionosonde. In global-scale convection maps inferred from all Super Dual Auroral Radar Network (SuperDARN) radar measurements, the polar cap arcs were often seen close to the reversal line of additional mesoscale convection cells located poleward of the normal cells related to the auroral oval.