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Articles de revues sur le sujet « Vortice polare »

Auteur : Grafiati

Publié le 9 mars 2023

Mis à jour le 10 mars 2023

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1

Cavallo, Steven M., and Gregory J. Hakim. "Composite Structure of Tropopause Polar Cyclones." Monthly Weather Review 138, no. 10 (2010): 3840–57. http://dx.doi.org/10.1175/2010mwr3371.1.

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Abstract Tropopause polar vortices are coherent circulation features based on the tropopause in polar regions. They are a common feature of the Arctic, with typical radii less than 1500 km and lifetimes that may exceed 1 month. The Arctic is a particularly favorable region for these features due to isolation from the horizontal wind shear associated with the midlatitude jet stream, which may destroy the vortical circulation. Intensification of cyclonic tropopause polar vortices is examined here using an Ertel potential vorticity framework to test the hypothesis that there is an average tendency for diabatic effects to intensify the vortices due to enhanced upper-tropospheric radiative cooling within the vortices. Data for the analysis are derived from numerical simulations of a large sample of observed cyclonic vortices over the Canadian Arctic. Results show that there is on average a net tendency to create potential vorticity in the vortex, and hence intensify cyclones, and that the tendency is radiatively driven. While the effects of latent heating are considerable, they are smaller in magnitude, and all other diabatic processes have a negligible effect on vortex intensity.

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Guendelman, Ilai, Darryn W. Waugh, and Yohai Kaspi. "Dynamical Regimes of Polar Vortices on Terrestrial Planets with a Seasonal Cycle." Planetary Science Journal 3, no. 4 (2022): 94. http://dx.doi.org/10.3847/psj/ac54b6.

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Abstract Polar vortices are common planetary-scale flows that encircle the pole in the middle or high latitudes and are observed in most of the solar system’s planetary atmospheres. The polar vortices on Earth, Mars, and Titan are dynamically related to the mean meridional circulation and exhibit a significant seasonal cycle. However, the polar vortex’s characteristics vary between the three planets. To understand the mechanisms that influence the polar vortex’s dynamics and dependence on planetary parameters, we use an idealized general circulation model with a seasonal cycle in which we vary the obliquity, rotation rate, and orbital period. We find that there are distinct regimes for the polar vortex seasonal cycle across the parameter space. Some regimes have similarities to the observed polar vortices, including a weakening of the polar vortex during midwinter at slow rotation rates, similar to Titan’s polar vortex. Other regimes found within the parameter space have no counterpart in the solar system. In addition, we show that for a significant fraction of the parameter space, the vortex’s potential vorticity latitudinal structure is annular, similar to the observed structure of the polar vortices on Mars and Titan. We also find a suppression of storm activity during midwinter that resembles the suppression observed on Mars and Earth, which occurs in simulations where the jet velocity is particularly strong. This wide variety of polar vortex dynamical regimes that shares similarities with observed polar vortices, suggests that among exoplanets there can be a wide variability of polar vortices.

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Guendelman, Ilai, Darryn W. Waugh, and Yohai Kaspi. "Dynamical Regimes of Polar Vortices on Terrestrial Planets with a Seasonal Cycle." Planetary Science Journal 3, no. 4 (2022): 94. http://dx.doi.org/10.3847/psj/ac54b6.

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Abstract Polar vortices are common planetary-scale flows that encircle the pole in the middle or high latitudes and are observed in most of the solar system’s planetary atmospheres. The polar vortices on Earth, Mars, and Titan are dynamically related to the mean meridional circulation and exhibit a significant seasonal cycle. However, the polar vortex’s characteristics vary between the three planets. To understand the mechanisms that influence the polar vortex’s dynamics and dependence on planetary parameters, we use an idealized general circulation model with a seasonal cycle in which we vary the obliquity, rotation rate, and orbital period. We find that there are distinct regimes for the polar vortex seasonal cycle across the parameter space. Some regimes have similarities to the observed polar vortices, including a weakening of the polar vortex during midwinter at slow rotation rates, similar to Titan’s polar vortex. Other regimes found within the parameter space have no counterpart in the solar system. In addition, we show that for a significant fraction of the parameter space, the vortex’s potential vorticity latitudinal structure is annular, similar to the observed structure of the polar vortices on Mars and Titan. We also find a suppression of storm activity during midwinter that resembles the suppression observed on Mars and Earth, which occurs in simulations where the jet velocity is particularly strong. This wide variety of polar vortex dynamical regimes that shares similarities with observed polar vortices, suggests that among exoplanets there can be a wide variability of polar vortices.

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Waugh, Darryn W., Adam H. Sobel, and Lorenzo M. Polvani. "What Is the Polar Vortex and How Does It Influence Weather?" Bulletin of the American Meteorological Society 98, no. 1 (2017): 37–44. http://dx.doi.org/10.1175/bams-d-15-00212.1.

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Abstract The term polar vortex has become part of the everyday vocabulary, but there is some confusion in the media, general public, and science community regarding what polar vortices are and how they are related to various weather events. Here, we clarify what is meant by polar vortices in the atmospheric science literature. It is important to recognize the existence of two separate planetary-scale circumpolar vortices: one in the stratosphere and the other in the troposphere. These vortices have different structures, seasonality, dynamics, and impacts on extreme weather. The tropospheric vortex is much larger than its stratospheric counterpart and exists year-round, whereas the stratospheric polar vortex forms in fall but disappears in the spring of each year. Both vortices can, in some circumstances, play a role in extreme weather events at the surface, such as cold-air outbreaks, but these events are not the consequence of either the existence or gross properties of these two vortices. Rather, cold-air outbreaks are most directly related to transient, localized displacements of the edge of the tropospheric polar vortex that may, in some circumstances, be related to the stratospheric polar vortex, but there is no known one-to-one connection between these phenomena.

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Dawber, Matthew. "Balancing polar vortices and stripes." Nature Materials 16, no. 10 (2017): 971–72. http://dx.doi.org/10.1038/nmat4962.

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Roscoe, H. K. "Measuring air from polar vortices." Nature 350, no. 6315 (1991): 197–98. http://dx.doi.org/10.1038/350197c0.

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Shultis, J., D. W. Waugh, A. D. Toigo, C. E. Newman, N. A. Teanby, and J. Sharkey. "Winter Weakening of Titan's Stratospheric Polar Vortices." Planetary Science Journal 3, no. 4 (2022): 73. http://dx.doi.org/10.3847/psj/ac5ea1.

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Abstract Polar vortices are a prominent feature in Titan's stratosphere. The Cassini mission has provided a detailed view of the breakdown of the northern polar vortex and formation of the southern vortex, but the mission did not observe the full annual cycle of the evolution of the vortices. Here we use a TitanWRF general circulation model simulation of an entire Titan year to examine the full annual cycle of the polar vortices. The simulation reveals a winter weakening of the vortices, with a clear minimum in polar potential vorticity and midlatitude zonal winds between winter solstice and spring equinox. The simulation also produces the observed postfall equinox cooling followed by rapid warming in the upper stratosphere. This warming is due to strong descent and adiabatic heating, which also leads to the formation of an annular potential vorticity structure. The seasonal evolution of the polar vortices is very similar in the two hemispheres, with only small quantitative differences that are much smaller than the seasonal variations, which can be related to Titan's orbital eccentricity. This suggests that any differences between observations of the northern hemisphere vortex in late northern winter and the southern hemisphere vortex in early winter are likely due to the different observation times with respect to solstice, rather than fundamental differences in the polar vortices.

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BUSH, JOHN W. M., and ANDREW W. WOODS. "Vortex generation by line plumes in a rotating stratified fluid." Journal of Fluid Mechanics 388 (June 10, 1999): 289–313. http://dx.doi.org/10.1017/s0022112099004759.

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We present the results of an experimental investigation of the generation of coherent vortical structures by buoyant line plumes in rotating fluids. Both uniform and stratified ambients are considered. By combining the scalings describing turbulent plumes and geostrophically balanced vortices, we develop a simple model which predicts the scale of the coherent vortical structures in excellent accord with laboratory experiments.We examine the motion induced by a constant buoyancy flux per unit length B, released for a finite time ts, from a source of length L into a fluid rotating with angular speed Ω = f/2. When the plume discharges into a uniformly stratified environment characterized by a constant Brunt–Väisälä frequency, N>f, the fluid rises to its level of neutral buoyancy unaffected by the system rotation before intruding as a gravity current. Rotation has a strong impact on the subsequent dynamics: shear develops across the spreading neutral cloud which eventually goes unstable, breaking into a chain of anticyclonic lenticular vortices. The number of vortices n emerging from the instability of the neutral cloud, n = (0.65±0.1)Lf1/2/ (t1/2sB1/3), is independent of the ambient stratification, which serves only to prescribe the intrusion height and aspect ratio of the resulting vortex structures. The experiments indicate that the Prandtl ratio characterizing the geostrophic vortices is given by P = Nh/(fR) = 0.47±0.12; where h and R are, respectively, the half-height and radius of the vortices. The lenticular vortices may merge soon after formation, but are generally stable and persist until they are spun-down by viscous effects.When the fluid is homogeneous, the plume fluid rises until it impinges on a free surface. The nature of the flow depends critically on the relative magnitudes of the layer depth H and the rotational lengthscale Lf = B1/3/f. For H>10Lf, the ascent phase of the plume is influenced by the system rotation and the line plume breaks into a series of unstable anticylonic columns of characteristic radius (5.3±1.0)B1/3/f which typically interact and lose their coherence before surfacing. When H<10Lf, the system rotation does not influence the plume ascent, but does control the spreading of the gravity current at the free surface. In a manner analogous to that observed in the stratified ambient, shear develops across the surface current, which eventually becomes unstable and generates a series of anticyclonic surface eddies with characteristic radius (1.6±0.2)B1/3t1/3s /f2/3. These surface eddies are significantly more stable than their columnar counterparts, but less so than the lenticular eddies arising in the uniformly stratified ambient.The relevance of the study to the formation of coherent vortical structures by leads in the polar ocean and hydrothermal venting is discussed.

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Garcia, Ferran, Frank R. N. Chambers, and Anna L. Watts. "Deep model simulation of polar vortices in gas giant atmospheres." Monthly Notices of the Royal Astronomical Society 499, no. 4 (2020): 4698–715. http://dx.doi.org/10.1093/mnras/staa2962.

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ABSTRACT The Cassini and Juno probes have revealed large coherent cyclonic vortices in the polar regions of Saturn and Jupiter, a dramatic contrast from the east–west banded jet structure seen at lower latitudes. Debate has centred on whether the jets are shallow, or extend to greater depths in the planetary envelope. Recent experiments and observations have demonstrated the relevance of deep convection models to a successful explanation of jet structure, and cyclonic coherent vortices away from the polar regions have been simulated recently including an additional stratified shallow layer. Here we present new convective models able to produce long-lived polar vortices. Using simulation parameters relevant for giant planet atmospheres we find flow regimes of geostrophic turbulence (GT) in agreement with rotating convection theory. The formation of large-scale coherent structures occurs via 3D upscale energy transfers. Our simulations generate polar characteristics qualitatively similar to those seen by Juno and Cassini: They match the structure of cyclonic vortices seen on Jupiter; or can account for the existence of a strong polar vortex extending downwards to lower latitudes with a marked spiral morphology, and the hexagonal pattern seen on Saturn. Our findings indicate that these vortices can be generated deep in the planetary interior. A transition differentiating these two polar flows regimes is described, interpreted in terms of force balances and compared with shallow atmospheric models characterizing polar vortex dynamics in giant planets. In addition, heat transport properties are investigated, confirming recent scaling laws obtained with reduced models of GT.

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Li, Qian, Vladimir A. Stoica, Marek Paściak, et al. "Subterahertz collective dynamics of polar vortices." Nature 592, no. 7854 (2021): 376–80. http://dx.doi.org/10.1038/s41586-021-03342-4.

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Waugh, Darry N. W. "Elliptical diagnostics of stratospheric polar vortices." Quarterly Journal of the Royal Meteorological Society 123, no. 542 (1997): 1725–48. http://dx.doi.org/10.1002/qj.49712354213.

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12

Waugh, D. W., A. D. Toigo, S. D. Guzewich, S. J. Greybush, R. J. Wilson, and L. Montabone. "Martian polar vortices: Comparison of reanalyses." Journal of Geophysical Research: Planets 121, no. 9 (2016): 1770–85. http://dx.doi.org/10.1002/2016je005093.

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Toigo, A. D., D. W. Waugh, and S. D. Guzewich. "What causes Mars' annular polar vortices?" Geophysical Research Letters 44, no. 1 (2017): 71–78. http://dx.doi.org/10.1002/2016gl071857.

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O’Neill, Morgan E., Kerry A. Emanuel, and Glenn R. Flierl. "Weak Jets and Strong Cyclones: Shallow-Water Modeling of Giant Planet Polar Caps." Journal of the Atmospheric Sciences 73, no. 4 (2016): 1841–55. http://dx.doi.org/10.1175/jas-d-15-0314.1.

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Abstract Giant planet tropospheres lack a solid, frictional bottom boundary. The troposphere instead smoothly transitions to a denser fluid interior below. However, Saturn exhibits a hot, symmetric cyclone centered directly on each pole, bearing many similarities to terrestrial hurricanes. Transient cyclonic features are observed at Neptune’s South Pole as well. The wind-induced surface heat exchange mechanism for tropical cyclones on Earth requires energy flux from a surface, so another mechanism must be responsible for the polar accumulation of cyclonic vorticity on giant planets. Here it is argued that the vortical hot tower mechanism, claimed by Montgomery et al. and others to be essential for tropical cyclone formation, is the key ingredient responsible for Saturn’s polar vortices. A 2.5-layer polar shallow-water model, introduced by O’Neill et al., is employed and described in detail. The authors first explore freely evolving behavior and then forced-dissipative behavior. It is demonstrated that local, intense vertical mass fluxes, representing baroclinic moist convective thunderstorms, can become vertically aligned and accumulate cyclonic vorticity at the pole. A scaling is found for the energy density of the model as a function of control parameters. Here it is shown that, for a fixed planetary radius and deformation radius, total energy density is the primary predictor of whether a strong polar vortex forms. Further, multiple very weak jets are formed in simulations that are not conducive to polar cyclones.

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Bray, Matthew T., and Steven M. Cavallo. "Characteristics of long-track tropopause polar vortices." Weather and Climate Dynamics 3, no. 1 (2022): 251–78. http://dx.doi.org/10.5194/wcd-3-251-2022.

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Abstract. Tropopause polar vortices (TPVs) are closed circulations centered on the tropopause that form and predominately reside in high latitudes. Due to their attendant flow, TPVs have been shown to influence surface weather features, and thus, a greater understanding of the dynamics of these features may improve our ability to forecast impactful weather events. In this study, we focus on the subset of TPVs that have lifetimes of longer than 2 weeks (the 95th percentile of all TPV cases between 1979 and 2018); these long-lived vortices offer a unique opportunity to study the conditions under which TPVs strengthen and analyze patterns of vortex formation and movement. Using ERA-Interim data, along with TPV tracks derived from the same reanalysis, we investigate the formation, motion, and development of these long-lived vortices. We find that these TPVs are significantly stronger, occur more often in the summer, and tend to remain more poleward than an average TPV. Similarly, these TPVs are shown to form at higher latitudes than average. Long-lived TPVs form predominately by splitting from existing vortices, but a notable minority seem to generate via dynamic processes in the absence of pre-existing TPVs. These non-likely split genesis events are found to occur in select geographic regions, driven by Rossby wave growth and breaking. Seasonal variations emerge in the life cycles of long-lived vortices; notably, winter TPVs progress more equatorward and generally grow to stronger amplitudes. These long-lived TPVs also appear as likely as any TPV to exit the Arctic and move into the mid-latitudes, doing so via two primary pathways: through Canada or Siberia.

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Boatto, Stefanella, and Carles Simó. "A vortex ring on a sphere: the case of total vorticity equal to zero." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, no. 2158 (2019): 20190019. http://dx.doi.org/10.1098/rsta.2019.0019.

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The stability of a ring of vortices has attracted the interest of researchers for over a century. Recent beautiful observations of polygonal configurations of vortices present in the atmospheres of Jupiter and Saturn, and of polygonal jets in the Earth's atmosphere, have revived the interest in the subject. In the observed cases, the vortex ring is in the presence of a central vortex. We present analytical and numerical results about the linear, spectral and Lyapunov stability of a ring in the presence of polar vortices. Motivated by both atmospheric observations we considered the special case of total vorticity equal to zero. Such a case has also the very nice property of being universal , i.e. not depending on a choice of gauge. We considered the two cases of fixed and non-fixed polar vortices. A ring in the northern (respectively, southern) hemisphere is stabilized by the presence of a northern (respectively, southern) polar vortex of suitable strength, in agreement with what is observed numerically and atmospherically. This article is part of the theme issue ‘Topological and geometrical aspects of mass and vortex dynamics’.

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Liu, Liying, Zelin An, Ruzhi Wang, et al. "Atomic-scale polar vortices in Na0.5Bi0.5TiO3 grains." Ceramics International 48, no. 8 (2022): 11830–35. http://dx.doi.org/10.1016/j.ceramint.2022.01.053.

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Waugh, Darryn W., William J. Randel, Steven Pawson, Paul A. Newman, and Eric R. Nash. "Persistence of the lower stratospheric polar vortices." Journal of Geophysical Research: Atmospheres 104, no. D22 (1999): 27191–201. http://dx.doi.org/10.1029/1999jd900795.

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Yadav, A. K., C. T. Nelson, S. L. Hsu, et al. "Observation of polar vortices in oxide superlattices." Nature 530, no. 7589 (2016): 198–201. http://dx.doi.org/10.1038/nature16463.

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Ramesh, R. "Observation of Polar Vortices in Oxide Superlattices." Microscopy and Microanalysis 22, S3 (2016): 1246–47. http://dx.doi.org/10.1017/s1431927616007078.

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Gimeno, Luis, Laura de la Torre, Raquel Nieto, David Gallego, Pedro Ribera, and Ricardo García-Herrera. "A new diagnostic of stratospheric polar vortices." Journal of Atmospheric and Solar-Terrestrial Physics 69, no. 15 (2007): 1797–812. http://dx.doi.org/10.1016/j.jastp.2007.07.013.

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Brueshaber, Shawn R., Kunio M. Sayanagi, and Timothy E. Dowling. "Dynamical regimes of giant planet polar vortices." Icarus 323 (May 2019): 46–61. http://dx.doi.org/10.1016/j.icarus.2019.02.001.

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Goncharov, V., and V. Pavlov. "Cyclostrophic vortices in polar regions of rotating planets." Nonlinear Processes in Geophysics 8, no. 4/5 (2001): 301–11. http://dx.doi.org/10.5194/npg-8-301-2001.

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Abstract. Multi-petal, rotating vortices can form in two-dimensional flows consisting of an inviscid incompressible fluid under certain conditions. Such vortices are principally nonlinear thermo-hydrodynamical structures. The proper rotation of these structures which leads to time-dependent variations of the associated temperature field can be enregistred by a stationary observer. The problem is analyzed in the framework of the contour dynamics method (CDM). An analytical solution of the reduced equation for a contour curvature is found. We give a classification of the solutions and compare the obtained results with observational data.

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Constantin, Adrian, Darren G. Crowdy, Vikas S. Krishnamurthy, and Miles H. Wheeler. "Stuart-type polar vortices on a rotating sphere." Discrete & Continuous Dynamical Systems - A 41, no. 1 (2021): 201–15. http://dx.doi.org/10.3934/dcds.2020263.

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Dritschel, David G. "Ring Configurations of Point Vortices in Polar Atmospheres." Regular and Chaotic Dynamics 26, no. 5 (2021): 467–81. http://dx.doi.org/10.1134/s1560354721050026.

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Harvey, V. Lynn, Cora E. Randall, Erich Becker, et al. "Evaluation of the Mesospheric Polar Vortices in WACCM." Journal of Geophysical Research: Atmospheres 124, no. 20 (2019): 10626–45. http://dx.doi.org/10.1029/2019jd030727.

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Watanabe, Shun-ichi I., and Hiroshi Niino. "Genesis and Development Mechanisms of a Polar Mesocyclone over the Japan Sea." Monthly Weather Review 142, no. 6 (2014): 2248–70. http://dx.doi.org/10.1175/mwr-d-13-00226.1.

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Abstract A polar mesocyclone (PMC) observed over the Japan Sea on 30 December 2010 was studied using a nonhydrostatic mesoscale numerical model with a horizontal resolution of 2 km. The numerical simulation successfully reproduced the observed life cycle of the PMC. The results of the numerical simulation suggest that the life cycle of the PMC may be divided into three stages: an early development stage, in which a number of small vortices appear in a shear zone; a late development stage, which is characterized by the merger of vortices and the formation of a few larger vortices; and a mature stage, in which only a single PMC is present. During the early development stage, vortices are generated in the shear zones of strong updrafts in discrete cumulus convection cells. In contrast, during the late development stage, the vortices develop as a result of barotropic instability in the shear zone. A cloud-free eye and spiral cloud bands accompany the mature stage of a simulated PMC. A warm core structure also forms at the center of the PMC on account of adiabatic warming associated with downdrafts. The structures in the PMC during the mature stage resemble those of a tropical cyclone. Sensitivity experiments, in which sensible and latent heat fluxes from the sea surface and condensational heating were switched on/off, demonstrate that condensational heating is critical to the development of the PMC at all stages, and that sensible and latent heat fluxes play secondary roles.

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Scott, R. K., and D. G. Dritschel. "Vortex–Vortex Interactions in the Winter Stratosphere." Journal of the Atmospheric Sciences 63, no. 2 (2006): 726–40. http://dx.doi.org/10.1175/jas3632.1.

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Abstract This paper examines the interaction of oppositely signed vortices in the compressible (non-Boussinesq) quasigeostrophic system, with a view to understanding vortex interactions in the polar winter stratosphere. A series of simplifying approximations leads to a two-vortex system whose dynamical properties are determined principally by two parameters: the ratio of the circulation of the vortices and the vertical separation of their centroids. For each point in this two-dimensional parameter space a family of equilibrium solutions exists, further parameterized by the horizontal separation of the vortex centroids, which are stable for horizontal separations greater than a critical value. The stable equilibria are characterized by vortex deformations that generally involve stronger deformations of the larger and/or lower of the two vortices. For smaller horizontal separations, the equilibria are unstable and a strongly nonlinear, time-dependent interaction takes place, typically involving the shedding of material from the larger vortex while the smaller vortex remains coherent. Qualitatively, the interactions resemble previous observations of certain stratospheric sudden warmings that involved the interaction of a growing anticyclonic circulation with the cyclonic polar vortex.

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Susarla, Sandhya, Shanglin Hsu, Piush Behera, et al. "Probing Three-dimensional Chiral Domain Walls in Polar Vortices." Microscopy and Microanalysis 28, S1 (2022): 1770–71. http://dx.doi.org/10.1017/s1431927622007000.

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Yadav, A. K., C. T. Nelson, S. L. Hsu, et al. "Erratum: Corrigendum: Observation of polar vortices in oxide superlattices." Nature 534, no. 7605 (2016): 138. http://dx.doi.org/10.1038/nature17420.

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Cavallo, Steven M., and Gregory J. Hakim. "Radiative Impact on Tropopause Polar Vortices over the Arctic." Monthly Weather Review 140, no. 5 (2012): 1683–702. http://dx.doi.org/10.1175/mwr-d-11-00182.1.

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Abstract Tropopause polar vortices (TPVs) are commonly observed, coherent circulation features of the Arctic with typical radii as large as approximately 800 km. Intensification of cyclonic TPVs has been shown to be dominated by infrared radiation. Here the hypothesis is tested that while radiation alone may not be essential for TPV genesis, radiation has a substantial impact on the long-term population characteristics of cyclonic TPVs. A numerical model is used to derive two 10-yr climatologies of TPVs for both winter and summer: a control climatology with radiative forcing and an experimental climatology with radiative forcing withheld. Results from the control climatology are first compared to those from the NCEP–NCAR reanalysis project (NNRP), which indicates sensitivity to both horizontal grid resolution and the use of polar filtering in the NNRP. Smaller horizontal grid resolution of 60 km in the current study yields sample-mean cyclonic TPV radii that are smaller by a factor of ~2 compared to NNRP, and vortex track densities in the vicinity of the North Pole are considerably larger compared to NNRP. The experimental climatologies show that winter (summer) vortex maximum amplitude is reduced by 22.3% (38.0%), with a net tendency to weaken without radiation. Moreover, while the number and lifetime of cyclonic TPVs change little in winter without radiation, the number decreases 12% and the mean lifetime decreases 19% during summer without radiation. These results suggest that dynamical processes are primarily responsible for the genesis of the vortices, and that radiation controls their maximum intensity and duration during summer, when the destructive effect of ambient shear is weaker.

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Garfinkel, Chaim I., Dennis L. Hartmann, and Fabrizio Sassi. "Tropospheric Precursors of Anomalous Northern Hemisphere Stratospheric Polar Vortices." Journal of Climate 23, no. 12 (2010): 3282–99. http://dx.doi.org/10.1175/2010jcli3010.1.

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Abstract Regional extratropical tropospheric variability in the North Pacific and eastern Europe is well correlated with variability in the Northern Hemisphere wintertime stratospheric polar vortex in both the ECMWF reanalysis record and in the Whole Atmosphere Community Climate Model. To explain this correlation, the link between stratospheric vertical Eliassen–Palm flux variability and tropospheric variability is analyzed. Simple reasoning shows that variability in the North Pacific and eastern Europe can deepen or flatten the wintertime tropospheric stationary waves, and in particular its wavenumber-1 and -2 components, thus providing a physical explanation for the correlation between these regions and vortex weakening. These two pathways begin to weaken the upper stratospheric vortex nearly immediately, with a peak influence apparent after a lag of some 20 days. The influence then appears to propagate downward in time, as expected from wave–mean flow interaction theory. These patterns are influenced by ENSO and October Eurasian snow cover. Perturbations in the vortex induced by the two regions add linearly. These two patterns and the quasi-biennial oscillation (QBO) are linearly related to 40% of polar vortex variability during winter in the reanalysis record.

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Guzewich, Scott D., A. D. Toigo, and D. W. Waugh. "The effect of dust on the martian polar vortices." Icarus 278 (November 2016): 100–118. http://dx.doi.org/10.1016/j.icarus.2016.06.009.

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Watanabe, Shun-ichi I., Hiroshi Niino, and Wataru Yanase. "Climatology of Polar Mesocyclones over the Sea of Japan Using a New Objective Tracking Method." Monthly Weather Review 144, no. 7 (2016): 2503–15. http://dx.doi.org/10.1175/mwr-d-15-0349.1.

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Abstract Polar mesocyclones (PMCs) are mesoscale cyclonic vortices that develop poleward of the main polar front. This article reports on a new algorithm for the objective tracking of PMCs, including meso-β-scale vortices, which will facilitate the study of their climatology. The algorithm is based mainly on the vorticity field and consists of three parts: the identification of vortices, the connection of vortices at consecutive time steps, and discrimination between PMCs and synoptic-scale disturbances. The objective tracking method was applied to Mesoscale Analysis (MA) data provided by the Japan Meteorological Agency, which has a horizontal resolution of 5 km. The detected tracks of PMCs were confirmed by subjective analysis of the MA data and satellite images. The method used here to discriminate between PMCs and synoptic-scale disturbances differs from that used in previous studies, which is based on the difference between the sea surface temperature and the temperature at 500 hPa, but gives a consistent result. This objective tracking method was used to obtain the climatology of PMCs over the Sea of Japan, which were classified into three groups according to the regions where they attained their maximum intensity. In each region, the PMCs have different characteristics with respect to their direction of movement, size, and intensity, which are likely to be related to their environment or development mechanism.

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Günther, G., and M. Dameris. "Air mass exchange across the polar vortex edge during a simulated major stratospheric warming." Annales Geophysicae 13, no. 7 (1995): 745–56. http://dx.doi.org/10.1007/s00585-995-0745-0.

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Abstract. The dynamics of the polar vortex in winter and spring play an important role in explaining observed low ozone values. A quantification of physical and chemical processes is necessary to obtain information about natural and anthropogenic causes of fluctuations of ozone. This paper aims to contribute to answering the question of how permeable the polar vortex is. The transport into and out of the vortex ("degree of isolation") remains the subject of considerable debate. Based on the results of a three-dimensional mechanistic model of the middle atmosphere, the possibility of exchange of air masses across the polar vortex edge is investigated. Additionally the horizontal and vertical structure of the polar vortex is examined. The model simulation used for this study is related to the major stratospheric warming observed in February 1989. The model results show fair agreement with observed features of the major warming of 1989. Complex structures of the simulated polar vortex are illustrated by horizontal and vertical cross sections of potential vorticity and inert tracer. A three-dimensional view of the polar vortex enables a description of the vortex as a whole. During the simulation two vortices and an anticyclone, grouped together in a very stable tripolar structure, and a weaker, more amorphous anticyclone are formed. This leads to the generation of small-scale features. The results also indicate that the permeability of the vortex edges is low because the interior of the vortices remain isolated during the simulation.

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FORD, RUPERT, and STEFAN G. LLEWELLYN SMITH. "Scattering of acoustic waves by a vortex." Journal of Fluid Mechanics 386 (May 10, 1999): 305–28. http://dx.doi.org/10.1017/s0022112099004371.

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We investigate the scattering of a plane acoustic wave by an axisymmetric vortex in two dimensions. We consider vortices with localized vorticity, arbitrary circulation and small Mach number. The wavelength of the acoustic waves is assumed to be much longer than the scale of the vortex. This enables us to define two asymptotic regions: an inner, vortical region, and an outer, wave region. The solution is then developed in the two regions using matched asymptotic expansions, with the Mach number as the expansion parameter. The leading-order scattered wave field consists of two components. One component arises from the interaction in the vortical region, and takes the form of a dipolar wave. The other component arises from the interaction in the wave region. For an incident wave with wavenumber k propagating in the positive X-direction, a steepest descents analysis shows that, in the far-field limit, the leading-order scattered field takes the form i(π−θ)eikX+½cosθcot(½θ) (2π/kR)1/2ei(kR−π/4), where θ is the usual polar angle. This expression is not valid in a parabolic region centred on the positive X-axis, where kRθ2=O(1). A different asymptotic solution is appropriate in this region. The two solutions match onto each other to give a leading-order scattering amplitude that is finite and single-valued everywhere, and that vanishes along the X-axis. The next term in the expansion in Mach number has a non-zero far-field response along the X-axis.

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Cavallo, Steven M., and Gregory J. Hakim. "Potential Vorticity Diagnosis of a Tropopause Polar Cyclone." Monthly Weather Review 137, no. 4 (2009): 1358–71. http://dx.doi.org/10.1175/2008mwr2670.1.

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Abstract Long-lived coherent vortices located near the tropopause are often found over polar regions. Although these vortices are a commonly observed feature of the Arctic, and can have lifetimes longer than one month, little is known about the mechanisms that control their evolution. This paper examines mechanisms of intensity change for a cyclonic tropopause polar vortex (TPV) using an Ertel potential vorticity (EPV) diagnostic framework. Results from a climatology of intensifying cyclonic TPVs suggest that the essential dynamics are local to the vortex, rather than a consequence of larger-scale processes. This fact motivates a case study using a numerical model to investigate the role of diabatic mechanisms in the growth and decay of a particular cyclonic vortex. A component-wise breakdown of EPV reveals that cloud-top radiational cooling is the primary diabatic mechanism that intensifies the TPV during the growth phase. Increasing amounts of moisture become entrained into the vortex core at later times near Hudson Bay, allowing the destruction of potential vorticity near the tropopause due to latent heat release to become comparable to the radiational tendency to create potential vorticity.

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Henderson, G. S., J. C. McConnell, S. R. Beagley, and W. F. J. Evans. "Polar ozone depletion: Current status." Canadian Journal of Physics 69, no. 8-9 (1991): 1110–22. http://dx.doi.org/10.1139/p91-170.

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Rapid springtime depletion of column ozone (O3) is observed over the Antarctic during the austral spring. A much weaker springtime depletion is observed in the Arctic region. This depletion results from a complex chemical mechanism that involves the catalytic destruction of stratospheric ozone by chlorine. The chemical mechanism appears to operate between ~12–25 km in the colder regions of the polar winter vortices. During the polar night heterogeneous chemical reactions occur on the surface of polar stratospheric clouds that convert relatively inert reservoir Cl species such as HCl to active Cl species. These clouds form when temperatures drop below about 197 K and are ubiquitous throughout the polar winter region. At polar sunrise the reactive Cl species are photolysed, liberating large quantities of free Cl that subsequently catalytically destroys O3 with a mechanism involving the formation of the Cl2O2 dimer. The magnitude of the spring depletion is much greater in the Antarctic relative to the Arctic owing to the greater stability and longer duration of the southern polar vortex. Breakup of the intense high-latitude vortices in late (Antarctic) or early (Arctic) spring results in infilling of the ozone holes but adversely affects midlatitude ozone levels by diluting them with O3-depleted, ClO-rich high-latitude air. The magnitude of the Antarctic ozone depletion has been increasing since 1979 and its current depletion in October 1990 amounts to 60%. The increase in the size of the depletion is anticorrelated with increasing anthropogenic chlorofluorocarbon (CFCs) release. Adherence to the revised Montréal Protocol should result in a reduction of stratospheric halogen levels with subsequent amelioration of polar ozone depletion but the time constant for the atmosphere to return to pre-CFC levels is ~60–100 years.

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Waugh, Darryn W., and William J. Randel. "Climatology of Arctic and Antarctic Polar Vortices Using Elliptical Diagnostics." Journal of the Atmospheric Sciences 56, no. 11 (1999): 1594–613. http://dx.doi.org/10.1175/1520-0469(1999)056<1594:coaaap>2.0.co;2.

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Waugh, Darryn W. "Subtropical stratospheric mixing linked to disturbances in the polar vortices." Nature 365, no. 6446 (1993): 535–37. http://dx.doi.org/10.1038/365535a0.

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Salmelin, R. H., and M. M. Salomaa. "Ion mobility along superfluid vortices with polar cores ion3He-A." Journal of Physics C: Solid State Physics 20, no. 27 (1987): L689—L695. http://dx.doi.org/10.1088/0022-3719/20/27/003.

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Mitchell, D. M., A. J. Charlton-Perez, L. J. Gray, et al. "The nature of Arctic polar vortices in chemistry-climate models." Quarterly Journal of the Royal Meteorological Society 138, no. 668 (2012): 1681–91. http://dx.doi.org/10.1002/qj.1909.

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Mingalev, Igor V., Natalia M. Astafieva, Konstantin G. Orlov, Victor S. Mingalev, Oleg V. Mingalev, and Valery M. Chechetkin. "A Simulation Study of the Formation of Large-Scale Cyclonic and Anticyclonic Vortices in the Vicinity of the Intertropical Convergence Zone." ISRN Geophysics 2013 (March 20, 2013): 1–12. http://dx.doi.org/10.1155/2013/215362.

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A regional nonhydrostatic mathematical model of the wind system of the lower atmosphere, developed recently in the Polar Geophysical Institute, is utilized to investigate the initial stage of the origin of large-scale vortices at tropical latitudes. The model produces three-dimensional distributions of the atmospheric parameters in the height range from 0 to 15 km over a limited region of the Earth’s surface. Time-dependent modeling is performed for the cases when, at the initial moment, the simulation domain is intersected by the intertropical convergence zone (ITCZ). Calculations are made for various cases in which the initial forms of the intertropical convergence zone are different and contained convexities with distinct shapes, which are consistent with the results of satellite microwave monitoring of the Earth’s atmosphere. The results of modeling indicate that the origin of convexities in the form of the intertropical convergence zone, having distinct configurations, can lead to the formation of different large-scale vortices, in particular, a cyclonic vortex, a pair of cyclonic-anticyclonic vortices, and a pair of cyclonic vortices, during a period not longer than three days. The radii of these large-scale vortices are about 400–600 km. The horizontal wind velocity in these vortices can achieve values of 15–20 m/s in the course of time.

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Manney, Gloria L., and Zachary D. Lawrence. "The major stratospheric final warming in 2016: dispersal of vortex air and termination of Arctic chemical ozone loss." Atmospheric Chemistry and Physics 16, no. 23 (2016): 15371–96. http://dx.doi.org/10.5194/acp-16-15371-2016.

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Abstract. The 2015/16 Northern Hemisphere winter stratosphere appeared to have the greatest potential yet seen for record Arctic ozone loss. Temperatures in the Arctic lower stratosphere were at record lows from December 2015 through early February 2016, with an unprecedented period of temperatures below ice polar stratospheric cloud thresholds. Trace gas measurements from the Aura Microwave Limb Sounder (MLS) show that exceptional denitrification and dehydration, as well as extensive chlorine activation, occurred throughout the polar vortex. Ozone decreases in 2015/16 began earlier and proceeded more rapidly than those in 2010/11, a winter that saw unprecedented Arctic ozone loss. However, on 5–6 March 2016 a major final sudden stratospheric warming ("major final warming", MFW) began. By mid-March, the mid-stratospheric vortex split after being displaced far off the pole. The resulting offspring vortices decayed rapidly preceding the full breakdown of the vortex by early April. In the lower stratosphere, the period of temperatures low enough for chlorine activation ended nearly a month earlier than that in 2011 because of the MFW. Ozone loss rates were thus kept in check because there was less sunlight during the cold period. Although the winter mean volume of air in which chemical ozone loss could occur was as large as that in 2010/11, observed ozone values did not drop to the persistently low values reached in 2011.We use MLS trace gas measurements, as well as mixing and polar vortex diagnostics based on meteorological fields, to show how the timing and intensity of the MFW and its impact on transport and mixing halted chemical ozone loss. Our detailed characterization of the polar vortex breakdown includes investigations of individual offspring vortices and the origins and fate of air within them. Comparisons of mixing diagnostics with lower-stratospheric N2O and middle-stratospheric CO from MLS (long-lived tracers) show rapid vortex erosion and extensive mixing during and immediately after the split in mid-March; however, air in the resulting offspring vortices remained isolated until they disappeared. Although the offspring vortices in the lower stratosphere survived longer than those in the middle stratosphere, the rapid temperature increase and dispersal of chemically processed air caused active chlorine to quickly disappear. Furthermore, ozone-depleted air from the lower-stratospheric vortex core was rapidly mixed with ozone rich air from the vortex edge and midlatitudes during the split. The impact of the 2016 MFW on polar processing was the latest in a series of unexpected events that highlight the diversity of potential consequences of sudden warming events for Arctic ozone loss.

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Sun, Yuanwei, Adeel Y. Abid, Congbing Tan, et al. "Subunit cell–level measurement of polarization in an individual polar vortex." Science Advances 5, no. 11 (2019): eaav4355. http://dx.doi.org/10.1126/sciadv.aav4355.

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Recently, several captivating topological structures of electric dipole moments (e.g., vortex, flux closure) have been reported in ferroelectrics with reduced size/dimensions. However, accurate polarization distribution of these topological ferroelectric structures has never been experimentally obtained. We precisely measure the polarization distribution of an individual ferroelectric vortex in PbTiO3/SrTiO3 superlattices at the subunit cell level by using the atomically resolved integrated differential phase contrast imaging in an aberration-corrected scanning transmission electron microscope. We find, in vortices, that out-of-plane polarization is larger than in-plane polarization, and that downward polarization is larger than upward polarization. The polarization magnitude is closely related to tetragonality. Moreover, the contribution of the Pb─O bond to total polarization is highly inhomogeneous in vortices. Our precise measurement at the subunit cell scale provides a sound foundation for mechanistic understanding of the structure and properties of a ferroelectric vortex and lattice-charge coupling phenomena in these topological ferroelectric structures.

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Feng, Wen, and Milena Stanislavova. "On the vortices for the nonlinear Schrödinger equation in higher dimensions." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 376, no. 2117 (2018): 20170189. http://dx.doi.org/10.1098/rsta.2017.0189.

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We consider the nonlinear Schrödinger equation in n space dimensions and study the existence and stability of standing wave solutions of the form and For n =2 k , ( r j , θ j ) are polar coordinates in , j =1,2,…, k ; for n =2 k +1, ( r j , θ j ) are polar coordinates in , ( r k , θ k , z ) are cylindrical coordinates in , j =1,2,…, k −1. We show the existence of functions ϕ w , which are constructed variationally as minimizers of appropriate constrained functionals. These waves are shown to be spectrally stable (with respect to perturbations of the same type), if 1< p <1+4/ n . This article is part of the theme issue ‘Stability of nonlinear waves and patterns and related topics’.

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Fu, Shen-Ming, Jing-Ping Zhang, Jian-Hua Sun, and Tian-Bao Zhao. "Composite Analysis of Long-Lived Mesoscale Vortices over the Middle Reaches of the Yangtze River Valley: Octant Features and Evolution Mechanisms." Journal of Climate 29, no. 2 (2016): 761–81. http://dx.doi.org/10.1175/jcli-d-15-0175.1.

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ABSTRACT A 14-yr climatology is presented of the mesoscale vortices generated in the vicinity of the Dabie Mountains [Dabie vortices (DBVs)] in the Yangtze River valley. Analyzing these vortices using the Climate Forecast System Reanalysis (CFSR), DBVs were found to be a frequent type of summer mesoscale weather system, with a mean monthly frequency of 12.2. DBVs were mainly located in the middle and lower troposphere, and ~92% of them triggered precipitation. Most DBVs were short lived, and only 19.5% persisted for more than 12 h. Latent heat release associated with precipitation is a dominant factor for the DBV’s three-dimensional geometry features, life span, and intensity. The long-lived DBVs, all of which triggered torrential rainfall, were analyzed using a composite analysis under the normalized polar coordinates. Results indicate that these vortices generally moved eastward and northeastward, which corresponded to the vortices’ orientation, divergence, vorticity budget, and kinetic energy budget. The evolution of long-lived DBVs featured significant unevenness: those octants located at the front and on the right side of the vortices’ moving tracks were more favorable for their development and maintenance, while those octants located at the back and on the left side acted conversely. Convergence-related shrinking was the most favorable factor for the vortices’ development and persistence, while the tilting effect was a dominant factor accounting for their attenuation. Long-lived DBVs featured strong baroclinity, and the baroclinic energy conversion acted as the main energy source for the vortices’ evolution. In contrast, the barotropic energy conversion favored the vortices’ development and maintenance at first, and later triggered their dissipation.

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Lu, Guangming, Suzhi Li, Xiangdong Ding, Jun Sun, and Ekhard K. H. Salje. "Tip-induced flexoelectricity, polar vortices, and magnetic moments in ferroelastic materials." Journal of Applied Physics 129, no. 8 (2021): 084104. http://dx.doi.org/10.1063/5.0039509.

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Susarla, Sandhya, Pablo García-Fernández, Colin Ophus, et al. "Atomic Scale Crystal Field Mapping of Polar Vortices in Oxide Superlattices." Microscopy and Microanalysis 28, S1 (2022): 2590–92. http://dx.doi.org/10.1017/s1431927622009850.

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Plumb, R. Alan, Darryn W. Waugh, and Martyn P. Chipperfield. "The effects of mixing on tracer relationships in the polar vortices." Journal of Geophysical Research: Atmospheres 105, no. D8 (2000): 10047–62. http://dx.doi.org/10.1029/1999jd901023.

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