Rossby vortices as sources of global magnetic structures on the Sun

A numerical simulation of the process of generation of the magnetic field by Rossby vortices, whose horizontal scale is comparable to the solar radius, has been carried out. Long-lived vortices form global magnetic structures that drift together with vortices. Differential rotation in latitude leads to a longer lifetime of cyclones and corresponding magnetic structures. The cyclone and the magnetic structure travel in longitude with the velocity close to a corresponding differential rotation velocity and drift slowly poleward. The interaction of cyclones located in close latitudes makes one of them move to higher latitudes and the poloidal component of the magnetic field to intensify during the interaction.The formation of large-scale vortices was simulated, when the initial condition was specified by a grid of small-scale vortices with a random amplitude distribution. Merging of vortices of the same sign leads to the formation of large-scale vortices whose size is determined by the geometry of the problem and by the differential rotation profile.     

Relaxation of quantum vortices in type II superconductors and in neutron stars

The nonstationary dynamics of vortices in conventional type II superconductors and in neutron stars is examined in the Newtonian approximation. A relaxation equation is obtained for vortices approaching an equilibrium distribution after a change in an external magnetic field. The relaxation times are estimated for vortices in low-temperature superconductors and for proton vortices in the superconducting core of a neutron star. It is shown that the proton vortex system created by entrainment currents is rigidly coupled to the neutron vortices. Translated from Astrofizika, Vol. 52, No. 2, pp. 291–300 (May 2009).     

Long‐term evolution of the magnetic field generated by an ensemble of Rossby vortices

The evolution of the large‐scale component of the magnetic field generated by an ensemble of Rossby vortices is numerically simulated. The distribution of the Rossby vortices excited at the beginning of each Carrington rotation is determined from the analysis of Kitt Peak synoptic maps. Our model also considers 11‐year hydrodynamic and 22‐year magnetic field oscillations. In the vicinity of the Rossby vortices, the toroidal magnetic field is significantly amplified and the sign of the angle between the rope of the field lines and the equator is in accordance with observations for “normal” sunspots. We also suggest the possibility of the interpretation by our model of “abnormal” sunspot phenomena. We find that an inverse cascade, namely, the merging of Rossby vortices, gives rise to the formation of large‐scale hydrodynamic structures with a life‐time on the order of a solar cycle period. We conclude from this that the formation of such structures can thus explain the appearance of long‐lived, large‐scale component in the distribution of the magnetic field.     

Covariant formulation of the dynamical equations of quantum vortices in type II superconductors

We have derived the closed system of covariant equations which describe the motion of quantum vortices regarded as a two-2dimensional polarized liquid. We have obtained the covariant expressions of the forces acting on the vortices; from the equilibrium condition of these forces we have deduced the equation satisfied by the velocity field of the fluid. It is shown that this velocity field depends on the friction coefficient, the density of vortices and the superconducting current. From this closed system of equations we derived the relaxation equation when a variable magnetic field is applied. Published in Astrofizika, Vol. 50, No. 3, pp. 381–391 (August 2007).     

Simulations of high-latitude spots on Jupiter: Constraints on vortex strength and the deep wind

We combine high-resolution observations of the dynamical behavior of small vortices (diameters ?5000 km) located at latitude 60°N on Jupiter with forward modeling, using the EPIC atmospheric model, to address two open questions: the dependence of the zonal winds with depth, and the strength of vortices that are too small to apply cloud tracking to their internal structure. The observed drift rates of the vortices can only be reproduced in the model when the zonal winds increase slightly with depth below the cloud tops, with a vertical shear that is less than was measured at 7°N at the southern rim of a 5-μm hotspot by the Galileo Probe Doppler Wind Experiment (DWE). This supports the idea that Jupiter's vertical shear may vary significantly with latitude. Our simulations suggest that the morphology of the mergers between vortices mainly depends on their maximum tangential velocities, the best results occurring when the tangential velocity is close to the velocity difference of the alternating jets constraining the zone in which the vortices are embedded. We use this correlation, together with the high-resolution data available for the White Ovals, to derive an empirical relationship between the maximum tangential velocity of a jovian vortex and its size, normalized by the strength and size of the encompassing shear zone. The Great Red Spot stands out as a significant anomaly to this relationship, but interestingly it is becoming less so with time.     

Relaxation of the Angular Velocity of the Vela Pulsar Following Its First Eight Glitches

The theory of the relaxation of pulsar angular velocity is compared with observational data for the first eight glitches of the Vela pulsar. Solutions of the inverse problem in relaxation theory are obtained in the regions of exponential and linear relaxation in the core of the neutron star. From these solutions, a distribution of vortices is found that results in the observed relaxation of the pulsar's angular velocity. It is shown that the pinning of neutron vortices plays the primary role in the region of exponential relaxation, while in the region of linear relaxation one must allow for the variation of the angular velocity of the superfluid component.     

Large Eddy Simulation of typical dust devil-like vortices in highly convective Martian boundary layers at the Phoenix lander site

Physical characteristics of naturally formed convective vortices in the Phoenix Mars lander environment have been investigated on a relatively hot summer Martian arctic day. For this, the NCAR LES has been adapted and developed to conduct three micro-scale simulations of the Martian Convective Boundary Layer (CBL), in situations with and without geostrophic wind, and atmospheric radiative flux divergence. Time series analysis of the vortices’ properties is discussed. The study confirms the decrease of vortex populations in windy conditions and also illustrates that intense but small vortices are expected to be observed in higher geostrophic wind situations. This may lead to more dust migration rather than dust devil formation on windy days. The background (geostrophic) wind causes the vortices to become less cyclostrophically balanced.     

Pancake cyclones and anti-cyclones in the ionosphere

The formation of pancake cyclones and anticyclones in the E-region of the Earth's ionosphere is considered. It is shown that the vortices can be maintained by the neutral winds or by chemical reactions including the energy release caused by the triple collisions of atomic oxygen with neutrals. It is found that the variations of the magnetic fields induced by the vortices are not localized and decrease slowly far from the vortex core. They can be easily detected by ground based magnetometers or by facilities on board the low-orbiting satellites.     

Numerical simulations of the magnetic field distribution in a solar complex of activity

Powerful solar complexes of activity are supposed to result from the excitation of Rossby vortices within a thin layer beneath the convection zone. Numerical simulations demonstrate that Rossby vortices generate large-scale arc-like magnetic structures. It is shown that the most powerful complex of activity observed in June-July 1982 was likely to be a result of the excitation of a Rossby anticyclone rather than a cyclone.     

A case study of Kelvin-Helmholtz vortices on both flanks of the Earth's magnetotail

Kelvin-Helmholtz instability (KHI) is a fundamental fluid dynamical process that develops in a velocity shear layer. It is excited on the tail-flanks of the Earth's magnetosphere where the flowing magnetosheath plasma and the stagnant magnetospheric plasma sit adjacent to each other. This instability is thought to induce vortical structures and play an important role in plasma transport there. While KHI vortices have been detected, the earlier observations were performed only on one flank at a time and questions related to dawn-dusk asymmetry were not addressed. Here, we report a case where KHI vortices grow more or less simultaneously and symmetrically on both flanks, despite all the factors that may have broken the symmetry. Yet, energy distributions of ions in and around the vortices show a remarkable dawn-dusk asymmetry. Our results thus suggest that although the initiation and development of the KHI depend primarily on the macroscopic properties of the flow, the observed enhancement of ion energy transport around the dawn side vortices may be linked to microphysical processes including wave-particle interactions. Possible coupling between macro- and micro-scales, if it is at work, suggests a role for KHI not only within the Earth's magnetosphere (e.g., magnetopause and geomagnetic tail) but also in other regions where shear flows of magnetized plasma play important roles.     

On structure formation in the universe

The formation of structures in the universe is one of the most challenging problems of cosmology. In this paper, an attempt to explain the formation of galaxies through the generation of vortices (with dissipation) in an uniformly expanding perfect fluid is made. The equation governing the mean square vorticity for a turbulent (isotropic and homogeneous) fluid is derived. It is shown that the mechanism of stretching vortices could enhance the mean square vorticity as a function of time. However, ultimately expansion and dissipation dominate and the solution for the mean square vorticity reaches the prediction by linear theory.     

EPIC simulations of the merger of Jupiter's White Ovals BE and FA: altitude-dependent behavior

Observations of the merger of Jupiter's White Ovals BE and FA show altitude-dependent behavior that we seek to capture in numerical simulations. In particular, it was observed that the upper portions of the vortices orbited each other before merging, but the lower portions translated into each other without orbiting, a phenomenon we term the pair-orbit vertical dichotomy. To reproduce this dichotomy in the EPIC model, it is sufficient to have (i) a decrease with altitude of the background zonal winds above the cloud level with a scale height of ∼2.4, (ii) a height scale of the winds inside the vortices that is the same or larger, and (iii) a maximum tangential velocity in each vortex of ∼100 m s⁻¹ or larger. Condition (i) is expected from thermal-wind analyses, (ii) is consistent with thermal-wind and Shoemaker-Levy 9 debris-trajectory analyses, and (iii) is consistent with cloud-top wind tracking. The model generally does not reproduce the dichotomy for vortices with smaller vertical extent or weaker circulations. Our simulated mergers correctly reproduce the observed ∼9° separation at which vortices start to orbit in the upper layers before they merge and the ∼70% area ratio of the final vortex BA to the sum of BE and FA.     

Generation of the magnetic fields of pulsars

The influence of the effect of entrainment of superconducting protons by superfluid neutrons on the distribution of neutron vortices in a rotating neutron star is investigated. It is shown that the proton vortex clusters generated by entrainment currents create the magnetic structure of a neutron vortex. The average magnetic field induction in a neutron vortex is calculated. The presence of the magnetic field of a neutron vortex considerably alters the radius of the vortex zone. The width of the vortex-free zone at the surface of the neutron star’s core increases, reaching macroscopic values on the order of several meters. This result considerably changes earlier concepts of the distribution of neutron vortices in a neutron star. Translated from Astrofizika, Vol. 43, No. 3, pp. 377-386, July–September, 2000.     

Role of 3d-dispersive Alfven waves in coronal heating

Coronal heating is one of the unresolved puzzles in solar physics from decades. In the present paper we have investigated the dynamics of vortices to apprehend coronal heating problem. A three dimensional (3d) model has been developed to study propagation of dispersive Alfvén waves (DAWs) in presence of ion acoustic waves which results in excitation of DAW and evolution of vortices. Taking ponderomotive nonlinearity into account, development of these vortices has been studied. There are observations of such vortices in the chromosphere, transition region and also in the lower solar corona. These structures may play an important role in transferring energy from lower solar atmosphere to corona and result in coronal heating. Nonlinear interaction of these waves is studied in view of recent simulation work and observations of giant magnetic tornadoes in solar corona and lower atmosphere of sun by solar dynamical observatory (SDO).     

Shear flow driven counter rotating vortices in an inhomogeneous dusty magnetoplasma

The coupling of Shukla-Varma (SV) and convective cell modes is discussed in the presence of non-Boltzmannian electron response and parallel equilibrium shear flow. In the linear case, a new dispersion relation is derived and analyzed. It is found that the coupled SV and convective cell modes destabilize in the presence of electron shear flow. On the other hand, in the nonlinear regime, it is shown that Shukla-Varma mode driven counter rotating vortices can be formed for the system under consideration. It is found that these vortices move slowly by comparison with the ion acoustic or electron drift-wave driven counter rotating vortices. The relevance of the present investigation with regard to space plasmas is also pointed out.     

An explanation of the persistence of the Great Red Spot of Jupiter

An argument is given basing the persistence of the Great Red Spot of Jupiter on compensation of the natural decay of vorticity by collision with a portion of the vortices shed by the South boundary of the South Tropical Zone. The latter are deviated northward by Coriolis acceleration. The GRS itself is regarded as a Rankine vortex with a central depression revealing the coloration of a layer below.     

Acceleration and ejection of ring vortices as a mechanism for formation of jet components in AGN

Exact solutions are obtained for the two-dimensional hydrodynamic equations for symmetric configurations of two and four vortices in the presence of an arbitrary flow with a point singularity. These solutions describe the dynamics of a dipole toroidal vortex in accretion and wind flows within the active nuclei of galaxies. It is shown that in a converging (accretion) flow, as they are compressed along their major radius, toroidal vortices are ejected with acceleration along the axis of symmetry of the active nucleus, to form the components of a bilateral jet. For a symmetric flow, the increase in the velocity of the vortices is determined by the monopole component of the flow, and, when there is an asymmetry in the flow, also by the dipole component of the flow, which controls the asymmetry of the ejection.     

Vortices in strongly magnetized nonuniform electron-positron-ion plasmas

The nonlinear mode coupling equations for electrostatic and electromagnetic waves in strongly magnetized nonuniform electron-positron-ion plasmas are derived. It is found that a small fraction of stationary ions (or high-Z charged impurities) can be responsible for the formation of coherent vortices which are forbidden when the ions are absent. Such vortices might significantly affect the transport properties of electron-positron plasmas in external magnetic fields.     

Vertical structure of Jupiter's troposphere from nonlinear simulations of long-lived vortices

Numerical simulations of jovian vortices at tropical and temperate latitudes, under different atmospheric conditions, have been performed using the EPIC code [Dowling, T.E., Fisher, A.S., Gierasch, P.J., Harrington, J., LeBeau, R.P., Santori, C.M., 1998. Icarus 132, 221-238] to simulate the high-resolution observations of motions and of the lifetimes presented in a previous work [Legarreta, J., Sánchez-Lavega, A., 2005. Icarus 174, 178-191] and infer the vertical structure of Jupiter's troposphere. We first find that in order to reproduce the longevity and drift rate of the vortices, the Brunt-Väisälä frequency of the atmosphere in the upper troposphere (pressures P∼1 to 7 bar) should have a lower limit value of 5×¹⁰⁻³ s⁻¹, increasing upward up to 1.25×¹⁰⁻² s⁻¹ at pressures P∼0.5 bar (latitudes between 15° and 45° in both hemispheres). Second, the vortices drift also depend on the vertical structure of the zonal wind speed in the same range of altitudes. Simulations of the slowly drifting Southern hemisphere vortices (GRS, White Ovals and anticyclones at 40° S) require a vertically-constant zonal-wind with depth, but Northern hemisphere vortices (cyclonic “barges” and anticyclones at 19, 41 and 45° N) require decreasing winds at a rate of ∼5 m s⁻¹ per scale height. However vortices drifting at a high speed, close to or in the peak of East or West jets and in both hemispheres, require the wind speed slightly increasing with depth, as is the case for the anticyclones at 20° S and at 34° N. We deduce that the maximum absolute vertical shear of the zonal wind from P∼1 bar up to P∼7 bar in these jets is ∼15 m s⁻¹ per scale height. Intense vortices with tangential velocity at their periphery ∼100 m s⁻¹ tend to decay asymptotically to velocities ∼40 to 60 m s⁻¹ with a characteristic time that depends on the vortex intensity and static stability of the atmosphere. The vortices adjust their tangential velocity to the averaged peak to peak velocity of the opposed eastward and westward jets at their boundary. We show through our simulations that large-scale and long-lived vortices whose maximum tangential velocity is ∼100 m s⁻¹ can survive by absorbing smaller intense vortices.     

Renewed acceleration of the 24° N jet on Jupiter

Jupiter's eastward jet at 24° N, which formerly had the fastest winds on the planet, has maintained a less extreme speed of ∼135 m/s since 1991, carrying a series of long-lived vortices at 125 m/s. In 2002-2003, as the albedo of the adjacent North Temperate Belt increased, the tracks of the vortices accelerated slightly, and they had disappeared by 2005. In 2005, small tracers had a mean speed of 146.4 (±0.9) m/s, significantly faster than the previous mean speed of the jet, suggesting that the jet peak itself has accelerated at cloud-top level, and that the jet is beginning to return to the super-fast state. These changes may resemble the even greater transformations occurring in the equatorial jet of Saturn.