Polar Edge Research Articles

Ionospheric features of dayside polar cusp precipitation under the northward IMF

The geophysical processes in the dayside polar cusp on December 22, 2003 under the northern orientation of the interplanetary magnetic field (IMF), relatively high speed and low density of the solar wind by using the ground-based optical observations on Spitsbergen and DMSP F16 spacecraft observations were examined. A comparison of spacecraft and ground-based observations shows that soft electron precipitation in the cusp region determine the region of the auroral luminosity in the (OI) 630.0 nm emission. The peculiarity of the event under consideration is the observation of a bright rayed auroral arc bordering the dayside cusp from its polar edge. The results of observations of the low-altitude DMSP F16 spacecraft during its pass over the rayed arc were analyzed. Explanations of the observed phenomena are proposed based on the analysis of changes in the spectra of precipitating electrons and the formation of an electron beam by a field-aligned electric field.

Crosstalk analysis of multilayer graphene nanoribbon interconnects in GHz regime: Unraveling scattering induced effects

This paper analyzes the impact of high-frequency phenomena on the operational characteristics of intercalation-doped horizontal top-contact multilayer graphene nanoribbon (D-HTC-MLGNR) interconnects. The purpose is to explore their viability for utilization in high-frequency circuit design. A methodology incorporating the scattering-limited realistic mean free path and a finite thickness-dependent skin effect model is proposed for extracting the frequency-dependent impedance of MLGNR interconnects. By employing the proposed methodology, the frequency-dependent characteristics of scattering-limited impedance parameters and crosstalk effects in d-HTC-MLGNR interconnects are examined and compared with undoped MLGNR (viz. HTC and vertical top-contact) and copper (Cu) counterparts (smooth and rough). The findings indicate that Cu variants outperform scattering-limited MLGNR variants placed on SiO2 substrate in terms of crosstalk effects. However, Li-doped HTC-MLGNR without surface polar phonons (SPPs) and edge roughness (ER) placed on SiC and BN substrates demonstrates superior crosstalk-induced performance than Cu counterparts. Furthermore, in the absence of SPPs and ER, Li-D HTC-MLGNR placed on SiC has a minimum average percentage increase in overshoot peak amplitude, overshoot width, and delay of 6.6%, 0.18%, and 15.6%, respectively, for the entire frequency range, implying minimum impact of frequency variations and skin effect.

Gravity Wave–Induced Instability of the Stratospheric Polar Vortex Edge

Abstract We report on a previously undocumented process capable of mixing the Northern Hemisphere (NH) winter Ertel potential vorticity (EPV)—instabilities introduced along the stratospheric polar vortex edge by breaking gravity waves (GWs). As horizontal resolution has increased, global-scale atmospheric models and data assimilation systems (DASs) are now able to capture some aspects of GW generation, propagation, and dissipation, as well as mesoscale EPV disturbances. This work examines resolved GWs, their breaking, and their interaction with the stratospheric polar vortex as seen in the NASA Global Modeling and Assimilation Office DAS during the 2021–22 NH winter. This analysis shows that tropospheric-generated GWs, breaking in the stratosphere over a substantial area, created a significant disruption of the polar vortex EPV, in turn triggering baroclinic instabilities near the edge of the polar vortex. The instabilities take the form of mesoscale vortices propagating on the edge of the stratospheric polar vortex. This work reveals two new features in the EPV analysis: high and low fluctuations at the smallest model scale created by resolved GW breaking and high values associated with mesoscale vortices along the edge of the polar vortex. Significance Statement The Northern Hemisphere (NH) winter stratospheric polar vortex is typically disturbed by global-scale waves that displace, distort, and weaken the vortex; however, as the resolution of global models has increased, the role played by smaller-scale waves in disturbing the stratospheric vortex can now be evaluated. As one example, the NH winter of 2022 had unusually weak global-scale waves along with strong smaller-scale waves generated by flow over mountains, providing an ideal case for evaluating the effects brought about by the smaller-scale waves. Our examination of the 2022 NH winter reveals that the waves generated by flow over mountains, located under the stratospheric vortex, propagated up to the middle stratosphere where they broke down, interfering significantly with the vortex flow. This distortion of the vortex flow created an unstable region that led to the formation of “mesoscale vortices,” relatively small eddies on the edge of the polar vortex, that then propagated coherently around the stratospheric vortex. The importance of these small-scale wave-generated, mesoscale vortices may lie in their potential to mix trace gases across the stratospheric vortex boundary.

Orbital Hall Effect Accompanying Quantum Hall Effect: Landau Levels Cause Orbital Polarized Edge Currents.

The quantum Hall effect emerges when two-dimensional samples are subjected to strong magnetic fields at low temperatures: Topologically protected edge states cause a quantized Hall conductivity in multiples of e^{2}/h. Here we show that the quantum Hall effect is accompanied by an orbital Hall effect. Our quantum mechanical calculations fit well the semiclassical interpretation in terms of "skipping orbits." The chiral edge states of a quantum Hall system are orbital polarized akin to a hypothetical orbital version of the quantum anomalous Hall effect in magnetic systems. The orbital Hall resistivity scales quadratically with the magnetic field, making it the dominant effect at high fields.

Engineering ideal helical topological networks in stanene via Zn decoration

The xene family of topological insulators plays a key role in many proposals for topological electronic, spintronic, and valleytronic devices. These proposals rely on applying local perturbations, including electric fields and proximity magnetism, to induce topological phase transitions in xenes. However, these techniques lack control over the geometry of interfaces between topological regions, a critical aspect of engineering topological devices. We propose adatom decoration as a method for engineering atomically precise topological edge modes in xenes. Our first-principles calculations show that decorating stanene with Zn adatoms exclusively on one of two sublattices induces a topological phase transition from the quantum spin Hall (QSH) to quantum valley Hall (QVH) phase and confirm the existence of spin-valley polarized edge modes propagating at QSH/QVH interfaces. We conclude by discussing technological applications of these edge modes that are enabled by the atomic precision afforded by recent advances in adatom manipulation technology.

Object-oriented multi-scale segmentation and multi-feature fusion-based method for identifying typical fruit trees in arid regions using Sentinel-1/2 satellite images

Fruit tree identification that is quick and precise lays the groundwork for scientifically evaluating orchard yields and dynamically monitoring planting areas. This study aims to evaluate the applicability of time series Sentinel-1/2 satellite data for fruit tree classification and to provide a new method for accurately extracting fruit tree species. Therefore, the study area selected is the Tarim Basin, the most important fruit-growing region in northwest China. The main focus is on identifying several major fruit tree species in this region. Time series Sentinel-1/2 satellite images acquired from the Google Earth Engine (GEE) platform are used for the study. A multi-scale segmentation approach is applied, and six categories of features including spectral, phenological, texture, polarization, vegetation index, and red edge index features are constructed. A total of forth-four features are extracted and optimized using the Vi feature importance index to determine the best time phase. Based on this, an object-oriented (OO) segmentation combined with the Random Forest (RF) method is used to identify fruit tree species. To find the best method for fruit tree identification, the results are compared with three other widely used traditional machine learning algorithms: Support Vector Machine (SVM), Gradient Boosting Decision Tree (GBDT), and Classification and Regression Tree (CART). The results show that: (1) the object-oriented segmentation method helps to improve the accuracy of fruit tree identification features, and September satellite images provide the best time window for fruit tree identification, with spectral, phenological, and texture features contributing the most to fruit tree species identification. (2) The RF model has higher accuracy in identifying fruit tree species than other machine learning models, with an overall accuracy (OA) and a kappa coefficient (KC) of 94.60% and 93.74% respectively, indicating that the combination of object-oriented segmentation and RF algorithm has great value and potential for fruit tree identification and classification. This method can be applied to large-scale fruit tree remote sensing classification and provides an effective technical means for monitoring fruit tree planting areas using medium-to-high-resolution remote sensing images.

Cold Air Outbreaks in Winter over the Continental United States and Its Possible Linkage with Arctic Sea Ice Loss

The mechanism for the paradox of global warming and successive cold winters in mid-latitudes remains controversial. In this study, the connection between Arctic sea ice (ASI) loss and frequent cold air outbreaks in eastern Continental United States (CONUS) is explored. Two distinct periods of high and low ASI (hereafter high- and low-ice phases) are identified for comparative study. It is demonstrated that cold air outbreaks occur more frequently during the low-ice phase compared to that during the high-ice phase. The polar vortex is weakened and shifted southward during the low-ice phase. Correspondingly, the spatial pattern of 500 hPa geopotential height (GPH), which represents the mid-tropospheric circulation, shows a clear negative Arctic Oscillation-like pattern in the low-ice phase. Specifically, positive GPH anomalies in the Arctic region with two centers, respectively located over Greenland and the Barents Sea, significantly weaken the low-pressure system centered around the Baffin Island, and enhance Ural blocking in the low-ice phase. Meanwhile, the high ridge extending from Alaska to the west coast of North America further intensifies, while the low trough over eastern CONUS deepens. As a result, the atmospheric circulation in North America becomes more conductive to frigid Arctic air outbreaks. It is concluded that the ASI loss contributes to more cold air outbreaks in winter in eastern CONUS through the polar vortex weakening with southward displacement of the polar vortex edge, which lead to the weakening of the meridional potential vorticity gradient between the Arctic and mid-latitude and thus are conducive to the strengthening and long-term maintenance of the blocking high.

Polarization imaging and edge detection with image-processing metasurfaces

Optical metasurfaces have been recently explored as ultrathin analog image differentiators. By tailoring the momentum transfer function, they can perform efficient Fourier filtering—and thus potentially any linear mathematical operation—on an input image, replacing bulky 4f systems. While this approach has been investigated in different platforms, and a few techniques have been explored to achieve the required angular response, little effort has been devoted so far to tailor and control also the polarization response of an image-processing metasurface. Here, we show that edge-detection metasurfaces can be designed with tailored polarization responses, while simultaneously preserving an isotropic response. In particular, we demonstrate numerically and experimentally single-layer silicon metasurfaces yielding efficient Laplacian operation on a 2D image with either large polarization asymmetry, or nearly polarization-independent response. In the former case, we show that a strongly asymmetric polarization response can be used to unlock more sophisticated on-the-fly image processing functionalities, such as dynamically tunable direction-dependent edge detection. In parallel, metasurfaces with dual-polarized response are shown to enable efficient operation for unpolarized or arbitrarily polarized images, ensuring high efficiency. For both devices, we demonstrate edge detection within relatively large numerical apertures and with excellent isotropy and intensity throughput. Our study paves the way for the broad use of optical metasurfaces for sophisticated, massively parallel analog image processing with zero energy requirements.

Ultra-long dendroscales of the high latitudes in North America and the high latitudes in Eurasia

Based on 7,000-year tree-ring chronologies for the Pinus aristata from the tree line of White Mountains and Great Basin of North America (Ferguson’s scale), and Larix sibirica from the polar forest edge on Yamal Peninsula (Northern Eurasia, Khantemirov’s scale) reconstructed the Holocene section from its climatic optimum to the present day. Mathematically precise global rhythm, which repeat three times on charts of dendrochronological scales with a frequency in 2,600 years, are revealed. The relationship of the stem growth with flctuations in level of the World Ocean, Caspian Sea and Arctic sea ice, as well as the development of global droughts, has been determined.Regularities of the climate change, synchronously recorded in ultra-long dendroscales of two continents of the Northern Hemisphere by astronomically accurate rhythm in 2,600 years, most reliably reflct the Earth’s climate in recent millennia and provide the only key to its prediction in future.

Differential depression of calcium lignosulfonate on chalcopyrite and molybdenite flotation with collector kerosene

Molybdenite is the main mineral for molybdenum extraction, which coexists with chalcopyrite in porphyry copper deposits. However, the separation of molybdenite from chalcopyrite by flotation uses large amounts of toxic depressants, causing financial, health and environmental concerns. In this study, an environmentally friendly depressant, calcium lignosulfonate, with a low price was explored to depress chalcopyrite in the presence of kerosene, a collector widely used to float molybdenite. Adsorption isotherms of calcium lignosulfonate on chalcopyrite and molybdenite surfaces and contact angles of chalcopyrite, molybdenite’s basal planes and edge planes in the absence and presence of calcium lignosulfonate and kerosene were determined to understand the adsorptions of calcium lignosulfonate on heterogeneous chalcopyrite and molybdenite surfaces and the subsequent interactions with kerosene. It was found that calcium lignosulfonate effectively depressed chalcopyrite flotation, but had little depression effect on molybdenite because the adsorption density of calcium lignosulfonate on chalcopyrite was significantly higher than that on molybdenite. Calcium lignosulfonate molecules were uniformly adsorbed on chalcopyrite and molybdenite despite the heterogeneous surfaces. In fact, calcium lignosulfonate adsorbed on polar metal ion sites of chalcopyrite surfaces, blocking the adsorption of kerosene from adsorbing on hydrophobic sulphur-rich phases. Analogously, calcium lignosulfonate adsorbed on polar edge planes of molybdenite with little interference with the adsorption of kerosene on hydrophobic basal planes.

Dynamic synergistic effects of large-scale three-dimensional circulation anomalies on the record-breaking cold wave in February 2021 in North America

In contrast to previous studies that mainly focused on the influence of the polar vortex in the horizontal circulation on the local cold air, this study uses the three-pattern decomposition of global atmospheric circulation (3P-DGAC) to reveal the dynamic synergistic effects of horizontal circulation, local meridional circulation, and local zonal circulation on cold waves, by examining the record-breaking extreme cold wave (ECW) in February 2021 across North America. In terms of horizontal circulation, this ECW is preceded by the strengthening of blocking highs over the North Pacific and North Atlantic that force the tropospheric polar vortex edge toward North America, resulting in the development of the North American trough. The strongly northwesterly wind caused by the North American trough strengthens the local meridional circulation over North America, transporting cold Arctic air to the mid-low latitudes. Meanwhile, the local meridional circulation over North America strengthens the ascending motion and subsequently promotes the development of local zonal circulation over the North Atlantic. In turn, the developed local zonal circulation reinforces the blocking highs over the two oceans, slowing the movement of the trough and ridge systems eastward and leading to a long duration for this ECW. The composite analysis further conforms that the vertical sinking motion corresponding to blocking highs over the two oceans is mainly contributed by the local zonal circulation, and the strong local zonal circulation over the North Atlantic could lengthen the duration of the cold wave by strengthening the blocking highs. This study suggests that 3P-DGAC is an effective tool for investigating the three-dimensional structural characteristics of anomalous circulations in ECWs.

Spin-valley polarized edge states in quasi-one-dimensional asymmetric kagome lattice

The spin-valley-related electronic properties of quasi-one-dimensional kagome lattices with intrinsic spin-orbit coupling are studied, based on the tight-binding formalism. Three types of kagome-lattice nanoribbons along the x-direction with various geometric boundaries are proposed, including two symmetric nanoribbons and one asymmetric one. It is found that two nonequivalent Dirac cones and helical edge states exist in all the three types of kagome-lattice nanoribbons at 1/3 filling. Among them in the asymmetric nanoribbon, the spin and valley are found to be locked to each other due to inversion symmetry breaking, resulting in spin-valley polarized edge states. Band structure and probability density of wave function show that the spin-up/-down edge states locate at the K/K′ valley, with opposite propagation direction at the upper and lower boundaries. Spin-resolved real-space local current confirms the spin-valley polarized helical edge state in the asymmetric nanoribbon. The device application of the asymmetric kagome-lattice nanoribbon is worth further investigation.

A Frontal Dust Storm in the Northern Hemisphere at Solar Longitude 97—An Unusual Observation by the Emirates Mars Mission

AbstractThe Emirates Mars Mission (EMM) science phase began in Martian Year 36, solar longitude 49, which is outside of the classical Mars dust storm season. EMM observed a distinct dust cloud at northern mid‐to‐high latitudes on 10 September 2021 (Martian Year 36, solar longitude 97). The dust cloud is an arc‐shaped dust storm, typically observed at the northern polar cap edge. This type of non‐season dust storm is a well‐known phenomenon, but this particular case is interesting because the dust cloud has frontal structure. A large atmospheric front is unusual in this location and season. Moreover, EMM's unique observational coverage adds value to this observation. EMM provided a sequence of four camera images, which are separated by just 2–3 hr. The dust cloud showed very little motion over 7–8 hr, that is, it is quasi‐stationary. We discuss relevant dynamical processes, supported by a consistency check with the Mars Climate Database.

Alternative mammalian strategies leading towards gastrulation: losing polar trophoblast (Rauber's layer) or gaining an epiblast cavity.

Using embryological data from 14 mammalian orders, the hypothesis is presented that in placental mammals, epiblast cavitation and polar trophoblast loss are alternative developmental solutions to shield the central epiblast from extraembryonic signalling. It is argued that such reciprocal signalling between the edge of the epiblast and the adjoining polar trophoblast or edge of the mural trophoblast or with the amniotic ectoderm is necessary for the induction of gastrulation. This article is part of the theme issue 'Extraembryonic tissues: exploring concepts, definitions and functions across the animal kingdom'.

Gravity Wave Morphology During the 2018 Sudden Stratospheric Warming Simulated by a Whole Neutral Atmosphere General Circulation Model

AbstractAtmospheric gravity waves (GWs) during the February 2018 sudden stratospheric warming (SSW) event are simulated using the T639L340 whole neutral atmosphere general circulation model. Their characteristic morphology around the drastically evolving polar vortex is revealed by three‐dimensional (3D) visualization and ray‐tracing analyses. The 3D morphology of simulated GWs is described for the three key days that represent the pre‐SSW conditions, the mature stage for the vortex splitting, and the late SSW. The combination of strong winds along the polar vortex edge and underneath the tropospheric winds with similar wind directions consist of the deep waveguide for the upward‐propagating GWs, forming GW hot spots in the middle atmosphere. The GW hot spots associated with the development of the SSW are limited to North America and Greenland, and they include the typical upward‐propagating orographic GWs with relatively long vertical wavelengths. Different types of characteristic GW signatures are also recognized around the Canadian sub‐vortex (CV). GWs having short vertical wavelengths form near the surface and obliquely propagate over long distances along the CV winds. The non‐orographic GWs with short vertical wavelengths form in the middle stratosphere through the spontaneous adjustment of flow imbalance around the CV. Those GWs cyclonically ascend into the mesosphere along CV winds.

Cellular patterns and dry convection in textured dust storms at the edge of Mars North Polar Cap

We present a study of textured local dust storms that develop at the northern polar cap boundary on Mars springtime. We have used images obtained with VMC and HRSC cameras onboard Mars Express and MARCI on MRO to analyze dust storms captured from March to July 2019 (Ls = 350° in MY 34–Ls = 54° in MY 35). The textured storms grow in the longitude sector 150°E-210°E centered at latitude ~60°N and exhibit spiral, filamentary and compact shapes that change and evolve rapidly in a daily basis. The storms translate by prevailing east and southeast winds with speeds 15–45 ms−1. In some areas of their interiors they show organized clusters of cells formed typically by 100 elements with sizes ~5–30 km with a length/width ratio ~ 1.2–3 in the wind direction. The cells have elongated downwind tails with lengths 4–8 times the cell size. The cells top altitudes are ~6–11 km above their surroundings. We propose that the spirals grow as baroclinic vortices within a vertically sheared eastward jet present at this epoch in Mars due to the intense meridional temperature gradient at the polar cap edge. We show using a simple one-dimensional model that the cells can be produced by shallow dry convection with dust acting as the heating source to generate the updrafts. These patterns resemble those seen in laboratory experiments and on clouds in Earth's atmosphere and can serve to comparatively elucidate and discern the different mechanisms at work in each case.

Relationship between area and wind speed along the edge of the Antarctic polar vortex

The Antarctic polar vortex forms in autumn, intensifies in the winter-spring period and decays in late spring. Inside the vortex in the lower stratosphere, favorable conditions are created for the annual spring ozone depletion. One of the conditions for the formation of the Antarctic ozone hole is the presence of a dynamic barrier along the vortex edge in the winter-spring period, which contributes to a decrease in temperature inside the vortex (necessary for the existence of polar stratospheric clouds) and prevents the penetration of air masses into the vortex. The dynamic barrier exists when the wind speed along the vortex edge in the lower stratosphere is at least 20 m/s. When the vortex area decreases below 10 million km2 , the dynamic barrier usually weakens, preceded by the vortex breakdown. The purpose of this work is to consider the relationship between the vortex area and the wind speed along the vortex edge using the Antarctic polar vortex as an example. To analyze the dynamics of the Antarctic polar vortex, we used a method based on vortex delineation, which makes it possible to calculate the vortex area and wind speed along the vortex edge using geopotential values determined from the maximum values of temperature gradient and wind speed and, thus, characterizing the polar vortex edges. Seasonal variations in the vortex area are mainly determined by the time of the beginning, peak and end of the polar night. In turn, seasonal changes in wind speed along the edge of the Antarctic vortex are additionally determined by the influence of the temperature of the lower subtropical stratosphere. To eliminate the influence of the seasonal variation, polynomial trends were removed from the time series of the parameters considered. We have shown that the relationship between the vortex area and the wind speed along the vortex edge can be traced for area values of less than 25 million km2 and more than 50 million km2 . At small values of the vortex area (< 25 million km2), during its formation and destruction, a positive correlation appears between the vortex area and the wind speed along the vortex edge. At high values of the vortex area (> 50 million km2), a negative correlation can be traced between the parameters studied.

Rossby Waves in Total Ozone over the Arctic in 2000–2021

The purpose of this work is to study Rossby wave parameters in total ozone over the Arctic in 2000–2021. We consider the averages in the January–March period, when stratospheric trace gases (including ozone) in sudden stratospheric warming events are strongly disturbed by planetary waves. To characterize the wave parameters, we analyzed ozone data at the latitudes of 50°N (the sub-vortex area), 60°N (the polar vortex edge) and 70°N (inner region of the polar vortex). Total ozone column (TOC) measurements over a 22-year time interval were used from the Total Ozone Mapping Spectrometer/Earth Probe and Ozone Mapping Instrument/Aura satellite observations. The TOC zonal distribution and variations in the Fourier spectral components with zonal wave numbers m = 1–5 are presented. The daily and interannual variations in TOC, amplitudes and phases of the spectral wave components, as well as linear trends in the amplitudes of the dominant quasi-stationary wave 1 (QSW1), are discussed. The positive TOC peaks inside the vortex in 2010 and 2018 alternate with negative ones in 2011 and 2020. The extremely low TOC at 70°N in 2020 corresponds to severe depletion of stratospheric ozone over the Arctic in strong vortex conditions due to anomalously low planetary wave activity and a high positive phase of the Arctic Oscillation. Interannual TOC variations in the sub-vortex region at 50°N are accompanied by a negative trend of −4.8 Dobson Units per decade in the QSW1 amplitude, statistically significant at 90% confidence level, while the trend is statistically insignificant in the vortex edge region and inside the vortex due to the increased variability in TOC and QSW1. The processes associated with quasi-circumpolar migration and quasi-stationary oscillation of the wave-1 phase depending on the polar vortex strength in 2020 and 2021 are discussed.

High-Luminance Microsized CH3NH3PbBr3 Single-Crystal-Based Light-Emitting Diodes via a Facile Liquid-Insulator Bridging Route.

Micro-/nanosized organic-inorganic hybrid perovskite single crystals (SCs) with appropriate thickness and high crystallinity are promising candidates for high-performance electroluminescent (EL) devices. However, their small lateral size poses a great challenge for efficient device construction and performance optimization, causing perovskite SC-based light-emitting diodes (PSC-LEDs) to demonstrate poor EL performance. Here, we develop a facile liquid-insulator bridging (LIB) strategy to fabricate high-luminance PSC-LEDs based on single-crystalline CH3NH3PbBr3 microflakes. By introducing a blade-coated poly(methyl methacrylate) (PMMA) insulating layer to effectively overcome the problems of leakage current and possible short circuits between electrodes, we achieve the reliable fabrication of PSC-LEDs. The LIB method also allows us to systematically boost the device performance through crystal growth regulation and device architecture optimization. Consequently, we realize the best CH3NH3PbBr3 microflake-based PSC-LED with an ultrahigh luminance of 136100 cd m-2 and a half-lifetime of 88.2 min at an initial luminance of ∼1100 cd m-2, which is among the highest for organic-inorganic hybrid perovskite LEDs reported to date. Moreover, we observe the strong polarized edge emission of the microflake-based PSC-LEDs with a high degree of polarization up to 0.69. Our work offers a viable approach for the development of high-performance perovskite SC-based EL devices.

Evolution of the intensity and duration of the Southern Hemisphere stratospheric polar vortex edge for the period 1979–2020

Abstract. The intensity and position of the Southern Hemisphere stratospheric polar vortex edge is evaluated as a function of equivalent latitude over the period 1979–2020 on three isentropic levels (475, 550, and 675 K) from ECMWF ERA-Interim reanalysis. The study also includes an analysis of the onset and breakup dates of the polar vortex, which are determined from wind thresholds (e.g., 15.2, 20, and 25 m s−1) along the vortex edge. The vortex edge is stronger in late winter, during September–October–November, with the period of strongest intensity occurring later at the lowermost level. During the same period, we observe a lower variability of the edge position. A long-term increase in the vortex edge intensity and break-up date is observed during 1979–1999, linked to the increase in the ozone hole. A long-term decrease in the vortex onset date related to the 25 m s−1 wind threshold is also observed at 475 K during this period. The solar cycle and to a lower extent the quasi-biennial oscillation (QBO) and El Niño–Southern Oscillation (ENSO) modulate the interannual evolution of the strength of the vortex edge and the vortex breakup dates. A stronger vortex edge and longer vortex duration are observed in solar minimum (minSC) years, with the QBO and ENSO further modulating the solar cycle influence, especially at 475 and 550 K: during west QBO (wQBO) phases, the difference between vortex edge intensity for minSC and maxSC years is smaller than during east QBO (eQBO) phases. The polar vortex edge is stronger and lasts longer for maxSC/wQBO years than for maxSC/eQBO years. ENSO has a weaker impact but the vortex edge is somewhat stronger during cold ENSO phases for both minSC and maxSC years.