Results for "S. Poedts"

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Nonlinear three wave interaction in pair plasmasJul 27 2010It is shown that nonlinear three-wave interaction, described by vector-product type nonlinearities, in pair plasmas implies much more restrictive conditions for a double energy transfer, as compared to electron-ion plasmas.
A new paradigm for solar coronal heatingApr 29 2009The solar coronal heating problem refers to the question why the temperature of the Sun's corona is more than two orders of magnitude higher than that of its surface. Almost 70 years after the discovery, this puzzle is still one of the major challenges ... More
Global convective cell formation in pair-ion plasmasMay 30 2008The global electrostatic mode in pair-ion plasmas is discussed for cylindric geometry and for a radially inhomogeneous equilibrium density. In the case of a Gaussian radial density profile, exact analytical eigen solutions are found in terms of the Kummer ... More
Features of ion acoustic waves in collisional plasmasFeb 12 2010The effects of friction on the ion acoustic (IA) wave in fully and partially ionized plasmas are studied. In a quasi-neutral electron-ion plasma the friction between the two species cancels out exactly and the wave propagates without any damping. If the ... More
Comment on 'Alfven Instability in a Compressible Flow' [Phys. Rev. Lett. 101, 245001 (2008)]Apr 28 2009In a recent paper [Y. Taroyan, Phys. Rev. Lett 101, 245001 (2008) it is claimed that a new MHD instability of the Alfven wave has been found: incompressible Alfven modes propagating in a compressible spatially varying flow were apparently exponentially ... More
Comment on "Drift instabilities in the solar corona within the multi-fluid description" [Astron. Astrophys. {\bf 481}, 853 (2008)]Nov 14 2008Mecheri and Marsch concluded that drift currents caused by density gradients can serve as an energy source for a plasma instability, in particular for the excitation of ion-cyclotron waves in the solar corona. It is pointed out that these authors overlooked ... More
Note on the role of friction-induced momentum conservation in the collisional drift wave instabilityMay 16 2008The collisional drift wave instability is reexamined taking into account the ion response in the direction parallel to the magnetic field lines, which appears due to friction with electrons and which can not be omitted in view of the momentum conservation. ... More
Perpendicular electron collisions in drift and acoustic wave instabilitiesDec 31 2008Perpendicular electron dynamics and the associated collisions are discussed in relation to the collisional drift wave instability. In addition, the limit of small parallel wave numbers of this instability is studied and it is shown to yield a reduced ... More
Electric fields in solar magnetic structures due to gradient driven instabilities: heating and acceleration of particlesSep 03 2009The electrostatic instabilities driven by the gradients of the density, temperature and magnetic field, are discussed in their application to solar magnetic structures. Strongly growing modes are found for some typical plasma parameters. These instabilities ... More
Drift waves in the corona: heating and acceleration of ions at frequencies far below the gyro frequencyJul 27 2010In the solar corona, several mechanisms of the drift wave instability can make the mode growing up to amplitudes at which particle acceleration and stochastic heating by the drift wave take place. The stochastic heating, well known from laboratory plasma ... More
The universally growing mode in the solar atmosphere: coronal heating by drift wavesJun 11 2009The heating of the plasma in the solar atmosphere is discussed within both frameworks of fluid and kinetic drift wave theory. We show that the basic ingredient necessary for the heating is the presence of density gradients in the direction perpendicular ... More
Growing drift-cyclotron modes in the hot solar atmosphereMay 31 2008Well-known analytical results dealing with ion cyclotron and drift waves and which follow from the kinetic theory are used and the dispersion equation, which describes coupled two modes, is solved numerically. The numerical results obtained by using the ... More
Kinetic instability of drift-Alfven waves in solar corona and stochastic heatingJul 28 2010The solar atmosphere is structured and inhomogeneous both horizontally and vertically. The omnipresence of coronal magnetic loops implies gradients of the equilibrium plasma quantities like the density, magnetic field and temperature. These gradients ... More
Solar nanoflares and other smaller energy release events as growing drift wavesSep 09 2009Rapid energy releases (RERs) in the solar corona extend over many orders of magnitude, the largest (flares) releasing an energy of $10^{25} $J or more. Other events, with a typical energy that is a billion times less, are called nanoflares. A basic difference ... More
On the effect of the inhomogeneous subsurface flows on the high degree solar p-modesApr 14 2005The observed power spectrum of high-degree solar p-modes (l>200) shows discrepancies with the power spectrum predicted by the stochastic excitement and damping theory. In an attempt to explain these discrepancies, the present paper is concerned with the ... More
Weak and strong regimes of incompressible magnetohydrodynamic turbulenceJul 06 2009It is shown that in the framework of the weak turbulence theory, the autocorrelation and cascade timescales are always of the same order of magnitude. This means that, contrary to the general belief, any model of turbulence which implies a large number ... More
Cumulative whistler instability in fast solar winds: Constraints of electron temperature anisotropyApr 12 2019Context. Solar outflows are a considerable source of free energy which accumulates in multiple forms like beaming (or drifting) components and/or temperature anisotropies. However, kinetic anisotropies of plasma particles do not grow indefinitely and ... More
On quantum plasma: a plea for a common senseJul 15 2012The quantum plasma theory has flourished in the past few years without much regard to the physical validity of the formulation or its connection to any real physical system. It is argued here that there is a very limited physical ground for the application ... More
Electrostatic ion perturbations in kinematically complex shear flowsApr 16 2015The scope of the present paper is to determine how ion electrostatic wave perturbations in plasma flows are influenced by the presence of a kinematically complex velocity shear. For this purpose we consider a model based on the following set of physical ... More
A modified orbital motion limited (OML) theoryOct 28 2011The validity of the orbital motion limited (OML) theory is reviewed with reference to the floating potential acquired by a spherical object immersed in a plasma. A new and perhaps more realistic approach for obtaining the floating potential is introduced ... More
Self Heating of Corona by Electrostatic Fields Driven by Sheared FlowsJan 03 2012A mechanism of self-heating of solar corona is pointed out. It is shown that the free energy available in the form of sheared flows gives rise to unstable electrostatic waves which accelerate the particles and heat them. The electrostatic perturbations ... More
On over-reflection and generation of Gravito-Alfven waves in solar-type starsApr 30 2007The dynamics of linear perturbations is studied in magnetized plasma shear flows with a constant shearing rate and with gravity-induced stratification. The general set of linearized equations is derived and the two-dimensional case is considered in detail. ... More
Is the Weibel instability enhanced by the suprathermal populations, or not?Apr 15 2010The kinetic instabilities of the Weibel-type are presently invoked in a large variety of astrophysical scenarios because anisotropic plasma structures are ubiquitous in space. The Weibel instability is driven by a temperature anisotropy which is commonly ... More
Response to Comment of Shukla and Akbari-MoghanjoughiAug 13 2012Aug 15 2012Shukla and Akbari-Moghanjoughi have {\it corrected} their Comment (see their version 1 on `arXiv:1207.7029v1) to EPL on our work [1] after receiving our Response from the Editors of EPL. We have a pleasant duty at hand to present our second Response to ... More
Kinetic instability of ion acoustic mode in permeating plasmasJun 19 2009In plasmas with electron drift (current) relative to static ions, the ion acoustic wave is subject to the kinetic instability which takes place if the directed electron speed exceeds the ion acoustic speed. The instability threshold becomes different ... More
Shaping the solar wind temperature anisotropy by the interplay of electron and proton instabilitiesDec 03 2016A variety of nonthermal characteristics like kinetic, e.g., temperature, anisotropies and suprathermal populations (enhancing the high energy tails of the velocity distributions) are revealed by the in-situ observations in the solar wind indicating quasistationary ... More
Firehose constraints for the solar wind suprathermal electronsApr 19 2016The indefinite increase of temperature predicted by the solar wind expansion in the direction parallel to the interplanetary magnetic field is already notorious for not being confirmed by the observations. In hot and dilute plasmas from space particle-particle ... More
Quasilinear approach of the cumulative whistler instability in fast solar winds: Constraints of electron temperature anisotropyApr 12 2019May 27 2019Context. Solar outflows are a considerable source of free energy which accumulates in multiple forms like beaming (or drifting) components and/or temperature anisotropies. However, kinetic anisotropies of plasma particles do not grow indefinitely and ... More
Effects of suprathermal electrons on the proton temperature anisotropy in space plasmas: Electromagnetic ion-cyclotron instabilityFeb 12 2016May 11 2016In collision-poor plasmas from space, e.g., the solar wind and planetary magnetospheres, the kinetic anisotropy of the plasma particles is expected to be regulated by the kinetic instabilities. Driven by an excess of ion (proton) temperature perpendicular ... More
Observational Characteristics of CMEs without Low Coronal SignaturesSep 04 2014Solar eruptions are usually associated with a variety of phenomena occurring in the low corona before, during, and after onset of eruption. Though easily visible in coronagraph observations, so-called stealth coronal mass ejections (CMEs) do not obviously ... More
Collisional energy transfer in two-component plasmasAug 18 2008The friction in plasmas consisting of two species with different temperatures is discussed together with the consequent energy transfer. It is shown that the friction between the two species has no effect on the ion acoustic mode in a quasi-neutral plasma. ... More
Amplification of compressional MHD waves in systems with forced entropy oscillationsSep 06 2007The propagation of compressional MHD waves is studied for an externally driven system. It is assumed that the combined action of the external sources and sinks of the entropy results in the harmonic oscillation of the entropy (and temperature) in the ... More
On electrostatic modes in multi-ion and pair-ion collisional plasmasMay 16 2008The physics of plasmas containing positive and negative ions is discussed with special attention to the recently produced pair-ion plasma containing ions of equal mass and opposite charge. The effects of the density gradient in the direction perpendicular ... More
Ion thermal effects in oscillating multi-ion plasma sheath theoryNov 03 2008The effects of ion temperature are discussed in a two-ion electron plasma and for a model applicable to the oscillating sheath theory that has recently been much in the focus of researchers. The differences between the fluid and kinetic models have been ... More
Modelling three-dimensional transport of solar energetic protons in a corotating interaction region generated with EUHFORIAJan 28 2019We introduce a new solar energetic particle (SEP) transport code that aims at studying the effects of different solar wind configurations on SEP events. We focus on the influence of varying solar wind velocities on the energy changes of SEPs, and study ... More
The Interplay of the Solar Wind Core and Suprathermal Electrons: A Quasilinear Approach for Firehose InstabilityJan 31 2019In the solar wind an equipartition of kinetic energy densities can be easily established between thermal and suprathermal electrons and the instability conditions are markedly altered by the interplay of these two populations. The new thresholds derived ... More
Acoustic oscillations in the field-free, gravitationally stratified Acoustic oscillations in the field-free, gravitationally stratified cavities under solar bipolar magnetic canopiesMay 14 2009The main goal is to study the dynamics of the gravitationally stratified, field-free cavities in the solar atmosphere, located under small-scale, cylindrical magnetic canopies, in response to explosive events in the lower-lying regions (due to granulation, ... More
Is the solar corona nonmodally self-heated?Oct 11 2004Recently it was pointed out that nonmodally (transiently and/or adiabatically) pre-amplified waves in shear flows, undergoing subsequent viscous damping, can ultimately heat the ambient flow. The key ingredient of this process is the ability of waves ... More
The Electron Firehose and Ordinary-Mode Instabilities in Space PlasmasJul 02 2013The selfgenerated wave fluctuations are particularly interesting in the solar wind and magnetospheric plasmas, where Coulomb collisions are rare and cannot explain the observed states of quasi-equilibrium. Linear theory predicts that the firehose and ... More
Modeling space plasma dynamics with anisotropic Kappa distributionsApr 02 2012Space plasmas are collisionpoor and kinetic effects prevail leading to wave fluctuations, which transfer the energy to small scales: wave-particle interactions replace collisions and enhance dispersive effects heating particles and producing suprathermal ... More
'Swing Absorption' of fast magnetosonic waves in inhomogeneous mediaAug 05 2004Oct 07 2004The recently suggested swing interaction between fast magnetosonic and Alfven waves (Zaqarashvili and Roberts 2002) is generalized to inhomogeneous media. We show that the fast magnetosonic waves propagating across an applied non-uniform magnetic field ... More
Electrostatic plasma instabilities driven by neutral gas flows in the solar chromosphereDec 19 2013We investigate electrostatic plasma instabilities of Farley-Buneman (FB) type driven by quasi-stationary neutral gas flows in the solar chromosphere. The role of these instabilities in the chromosphere is clarified. We find that the destabilizing ion ... More
Farley-Buneman Instability in the Solar ChromosphereFeb 25 2009The Farley-Buneman instability is studied in the partially ionized plasma of the solar chromosphere taking into account the finite magnetization of the ions and Coulomb collisions. We obtain the threshold value for the relative velocity between ions and ... More
Energy flux of Alfven waves in weakly ionized plasmaMay 29 2008The overshooting convective motions in the solar photosphere are frequently proposed as the source for the excitation of Alfv\'en waves. However, the photosphere is a) very weakly ionized, and, b) the dynamics of the plasma particles in this region is ... More
Constraints for the aperiodic O-mode streaming instabilityNov 06 2014Dec 21 2014In plasmas where the thermal energy density exceeds the magnetic energy density ($\beta_\parallel > 1$), the aperiodic ordinary mode (O-mode) instability is driven by an excess of parallel temperature $A = T_\perp /T_\parallel < 1$ (where $\parallel$ ... More
Magnetic clouds in the solar wind: A numerical assessment study of analytical modelsSep 17 2011Magnetic clouds (MCs) are "magnetized plasma clouds" moving in the solar wind. MCs transport magnetic flux and helicity away from the Sun. These structures are not stationary but feature temporal evolution as they propagate in the solar wind. Simplified ... More
The mechanism of Swing Absorption of fast magnetosonic waves in inhomogeneous mediaOct 11 2004The recently suggested swing interaction between fast magnetosonic and Alfv\'en waves (2002) is generalized to inhomogeneous media. We show that the fast magnetosonic waves propagating across an applied non-uniform magnetic field can parametrically amplify ... More
Observation-based modelling of magnetised Coronal Mass Ejections with EUHFORIAApr 15 2019Coronal Mass Ejections (CMEs) are the primary source of strong space weather disturbances at Earth. Their geoeffectiveness is largely determined by their dynamic pressure and internal magnetic fields, for which reliable predictions at Earth are not possible ... More
The Electron Temperature and Anisotropy in the Solar Wind. I. Comparison of the Core and Halo PopulationsFeb 26 2016Estimating the temperature of the solar wind particles and their anisotropies is particularly important for understanding the origin of these deviations from thermal equilibrium as well as their effects. In the absence of energetic events the velocity ... More
Overstability of acoustic waves in strongly magnetized anisotropic MHD shear flowsJul 25 2014Dec 08 2015We present a linear stability analysis of the perturbation modes in anisotropic MHD flows with velocity shear and strong magnetic field. Collisionless or weakly collisional plasma is described within the 16-momentum MHD fluid closure model, that takes ... More
Dissipation of parallel and oblique Alfvén-cyclotron waves: implications for minor ion heating in the solar windJun 17 2015We perform 2.5D hybrid simulations with massless fluid electrons and kinetic particle-in-cell ions to study the temporal evolution of ion temperatures, temperature anisotropies and velocity distribution functions in relation to the dissipation and turbulent ... More
Variation of proton flux profiles with the observer's latitude in simulated gradual SEP eventsOct 17 2013We study the variation of the shape of the proton intensity-time profiles in simulated gradual Solar Energetic Particle (SEP) events with the relative observer's position in space with respect to the main direction of propagation of an interplanetary ... More
Solar Wind Electron Strahls Associated with a High-Latitude CME: \emph{Ulysses} ObservationsMay 22 2014Counterstreaming beams of electrons are ubiquitous in coronal mass ejections (CMEs) - although their existence is not unanimously accepted as a necessary and/or sufficient signature of these events. We continue the investigations of a high-latitude CME ... More
Quasilinear Approach of the Whistler Heat-Flux Instability in the Solar WindMar 19 2019The hot beaming (or strahl) electrons responsible for the main electron heat-flux in the solar wind are believed to be self-regulated by the electromagnetic beaming instabilities, also known as the heat-flux instabilities. Here we report the first quasi-linear ... More
Acceleration of dust particles by vortex ringNov 11 2009It is shown that nonlinear interaction between large amplitude circularly polarized EM wave and dusty plasma leads to a nonstationary ponderomotive force which in turn produces a vortex ring, and magnetic field. Then the ensuing vortex ring in the direction ... More
Acoustic oscillations in a field-free cavity under solar small-scale bipolar magnetic canopyJan 18 2008Observations show the increase of high-frequency wave power near magnetic network cores and active regions in the solar lower atmosphere. This phenomenon can be explained by the interaction of acoustic waves with a magnetic field. We consider small-scale, ... More
Dynamics of a solar prominence tornado observed by SDO/AIA on 2012 November 7-8Aug 27 2015We study the detailed dynamics of a solar prominence tornado using time series of 171, 304, 193 and 211 {\AA} spectral lines obtained by Solar Dynamics Observatory/ Atmospheric Imaging Assembly during 2012 November 7-8. The tornado first appeared at 08:00 ... More
Fine and superfine structure of Decameter-Hectometer type II burst on 2011 June 7Aug 27 2015The characteristics of the type II bursts with herringbone structure observed both by ground based radio telescopes (UTR-2, URAN-2) and spaceborn spectrometers (STEREO A-B) are discussed. The burst was recorded on 7 June, 2011 in the frequency band 3--33~MHz. ... More
Interferometric Observations of the Quiet Sun at 20 and 25 MHz in May 2014Jun 22 2018Results of solar observations at 20 and 25 MHz by the UTR-2 (\textit{Ukrainian T-shaped Radio telescope of the second modification}) radio telescope in the interferometric session from 27 May to 2 June 2014 are presented. In such a case the different ... More
Formation and evolution of coronal rain observed by SDO/AIA on February 22, 2012Apr 14 2015The formation and dynamics of coronal rain are currently not fully understood. Coronal rain is the fall of cool and dense blobs formed by thermal instability in the solar corona towards the solar surface with acceleration smaller than gravitational free ... More
On the evolution of pre-flare patterns of a 3-dimensional model of AR 11429Jan 01 2018We apply a novel pre-flare tracking of sunspot groups towards improving the estimation of flare onset time by focusing on the evolution of the 3D magnetic field construction of AR 11429. The 3D magnetic structure is based on potential field extrapolation ... More
Linking two consecutive nonmerging magnetic clouds with their solar sourcesDec 21 2012On 15 May 2005, a huge interplanetary coronal mass ejection (ICME) was observed near Earth. It triggered one of the most intense geomagnetic storms of solar cycle 23 (Dst peak = -263 nT). This structure has been associated with the two-ribbon flare, filament ... More
Long-period oscillations of active region patterns: least-squares mapping on second-order curvesOct 05 2016Oct 06 2016Active regions (ARs) are the main sources of variety in solar dynamic events. Automated detection and identification tools need to be developed for solar features for a deeper understanding of the solar cycle. Of particular interest here are the dynamical ... More
Magnetic Field Configuration Models and Reconstruction Methods for Interplanetary Coronal Mass EjectionsSep 27 2012This study aims to provide a reference to different magnetic field models and reconstruction methods for interplanetary coronal mass ejections (ICMEs). In order to understand the differences in the outputs of those models and codes, we analyze 59 events ... More
Comparative analysis of solar radio bursts before and during CME propagationMar 28 2019As is well known, CME propagation often results in the fragmentation of the solar atmosphere on smaller regions of density (magnetic field) enhancement (depletion). It is expected that this type of fragmentation may have radio signatures. The general ... More
Quantifying shear-induced wave transformations in the solar windMar 20 2007The possibility of velocity shear-induced linear transformations of different magnetohydrodynamic waves in the solar wind is studied both analytically and numerically. A quantitative analysis of the wave transformation processes for all possible plasma-$\beta$ ... More
Self-heating and its possible relationship to chromospheric heating in slowly rotating starsSep 29 2009The efficiency of nonmodal self-heating by acoustic wave perturbations is examined. Considering different kinds of kinematically complex velocity patterns we show that nonmodal instabilities arising in these inhomogeneous flows may lead to significant ... More
Effect of gravitational stratification on the propagation of a CMEOct 25 2013Our aim is to study the role of gravitational stratification on the propagation of CMEs. In particular, we assess how it influences the speed and shape of CMEs and under what conditions the flux rope ejection becomes a CME or when it is quenched. We ran ... More
Self-heating in kinematically complex magnetohydrodynamic flowsNov 17 2012The non-modal self-heating mechanism driven by the velocity shear in kinematically complex magnetohydrodynamic (MHD) plasma flows is considered. The study is based on the full set of MHD equations including dissipative terms. The equations are linearized ... More
Simulating AIA observations of a flux rope ejectionJul 31 2014Extreme ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) are providing new insights into the early phase of CME evolution. Observations now show the ejection of magnetic flux ropes from ... More
Interplanetary spread of solar energetic protons near a high-speed solar wind streamMar 21 2019We study how a high-speed solar wind stream embedded in a slow solar wind influences the spread of solar energetic protons in interplanetary space. To model the energetic protons, we used a recently developed particle transport code that computes particle ... More
The Effect of Limited Sample Sizes on the Accuracy of the Estimated Scaling Parameter for Power-Law-Distributed Solar DataMay 23 2016Many natural processes exhibit power-law behavior. The power-law exponent is linked to the underlying physical process and therefore its precise value is of interest. With respect to the energy content of nanoflares, for example, a power-law exponent ... More
Halo Coronal Mass Ejections during Solar Cycle 24: reconstruction of the global scenario and geoeffectivenessDec 15 2017In this study we present a statistical analysis of 53 fast Earth-directed halo CMEs observed by the SOHO/LASCO instrument during the period Jan. 2009-Sep. 2015, and we use this CME sample to test the capabilities of a Sun-to-Earth prediction scheme for ... More
Slurm: fluid particle-in-cell code for plasma modelingFeb 24 2018Jun 24 2018With the approach of exascale computing era, particle-based models are becoming the focus of research due to their excellent scalability. We present a new code, Slurm, which implements the classic particle-in-cell algorithm for modeling magnetized fluids ... More
Investigation of Dynamics of Self-Similarly Evolving Magnetic CloudsOct 18 2010Magnetic clouds (MCs) are "magnetized plasma clouds" moving in the solar wind. MCs transport magnetic flux and helicity away from the Sun. These structures are not stationary but feature temporal evolution. Commonly, simplified MC models are considered. ... More
Multifluid modeling of magnetosonic wave propagtion in the solar chromosphere -- effects of impact ionization and radiative recombinationNov 25 2016In order to study chromospheric magnetosonic wave propagation including, for the first time, the effects of ion-neutral interactions in the partially ionized solar chromosphere, we have developed a new multi-fluid computational model, accounting for ionization ... More
Multifluid modeling of magnetosonic wave propagation in the solar chromosphere -- effects of impact ionization and radiative recombinationNov 25 2016Dec 01 2016In order to study chromospheric magnetosonic wave propagation including, for the first time, the effects of ion-neutral interactions in the partially ionized solar chromosphere, we have developed a new multi-fluid computational model, accounting for ionization ... More
Solar signatures and eruption mechanism of the 2010 August 14 CMEJan 30 2017On 2010 August 14, a wide-angled coronal mass ejection (CME) was observed. This solar eruption originated from a destabilized filament that connected two active regions and the unwinding of this filament gave the eruption an untwisting motion that drew ... More
A GPU-enabled implicit Finite Volume solver for the ideal two-fluid plasma model on unstructured gridsSep 07 2018Dec 23 2018This paper describes the main features of a pioneering unsteady solver for simulating ideal two-fluid plasmas on unstructured grids, taking profit of GPGPU (General-purpose computing on graphics processing units). The code, which has been implemented ... More
Rieger-type periodicity during solar cycles 14-24: estimation of dynamo magnetic field strength in the solar interiorMay 13 2016Solar activity undergoes a variation over time scales of several months known as Rieger-type periodicity, which usually occurs near maxima of sunspot cycles. An early analysis showed that the periodicity appears only in some cycles, and is absent in other ... More
Observational evidence of torus instability as trigger mechanism for coronal mass ejections: the 2011 August 4 filament eruptionJan 23 2014Solar filaments are magnetic structures often observed in the solar atmosphere and consist of plasma that is cooler and denser than their surroundings. They are visible for days -- and even weeks -- which suggests that they are often in equilibrium with ... More
Evidence for precursors of the coronal hole jets in solar bright pointsMar 01 2018A set of 23 observations of coronal jet events that occurred in coronal bright points has been analyzed. The focus was on the temporal evolution of the mean brightness before and during coronal jet events. In the absolute majority of the cases either ... More
Statistical properties of coronal hole rotation rates: Are they linked to the solar interior?Jun 14 2017The present paper discusses results of a statistical study of the characteristics of coronal hole (CH) rotation in order to find connections to the internal rotation of the Sun. The goal is to measure CH rotation rates and study their distribution over ... More
Multipoint study of successive coronal mass ejections driving moderate disturbances at 1 AUJun 04 2019We analyse in this work the propagation and geoeffectiveness of four successive coronal mass ejections (CMEs) that erupted from the Sun during 21--23 May 2013 and that were detected in interplanetary space by the Wind and/or STEREO-A spacecraft. All these ... More
Band insulator to Mott insulator transition in a bilayer Hubbard modelMar 27 2007The ground state phase diagram of the half-filled repulsive Hubbard model in a bilayer is investigated using cluster dynamical mean field theory. For weak to intermediate values of Coulomb repulsion $U$, the system undergoes a transition from a Mott insulating ... More
Modelling the VHE flare of 3C 279 using one zone leptonic modelSep 12 2011We model the simultaneous observations of the flat spectrum radio quasar 3C 279 at radio, optical, X-ray and very high energy (VHE) gamma ray energies during 2006 flare using a simple one zone leptonic model. We consider synchrotron emission due to cooling ... More
The Cauchy problem for metric-affine f(R)-gravity in presence of a Klein-Gordon scalar fieldMar 22 2010We study the initial value formulation of metric-affine f(R)-gravity in presence of a Klein-Gordon scalar field acting as source of the field equations. Sufficient conditions for the well-posedness of the Cauchy problem are formulated. This result completes ... More
Low metallicity AGB models: H profile in the 13C-pocket and the effect on the s-processMay 17 2010The 13C(a, n)16O reaction is the major neutron source in low mass asymptotic giant branch (AGB) stars, where the main and the strong s process components are synthesised. After a third dredge-up (TDU) episode, 13C burns radiatively in a thin pocket which ... More
Technological Strategy of Using Global Positioning System: An AnalysisJan 23 2010The Global Positioning System (GPS) is a U.S. space-based radionavigation system that provides reliable positioning, navigation, and timing services to civilian users on a continuous worldwide basis -- freely available to all. GPS provides specially coded ... More
Resonating valence bond wave function for the two dimensional fractional spin liquidAug 13 2003Feb 19 2004The unconventional low-lying spin excitations, recently observed in neutron scattering experiments on ${\rm Cs_2 Cu Cl_4}$, are explained with a spin liquid wave function. The dispersion relation as well as the wave vector of the incommensurate spin correlations ... More
On $T$-sequences and characterized subgroupsFeb 04 2009Mar 08 2009Let $X$ be a compact metrizable abelian group and $\mathbf{u}=\{u_n\}$ be a sequence in its dual $X^{\wedge}$. Set $s_{\mathbf{u}} (X)= \{x: (u_n,x)\to 1\}$ and $\mathbb{T}_0^H = \{(z_n)\in \mathbb{T}^{\infty} : z_n\to 1 \}$. Let $G$ be a subgroup of ... More
On the Ascoli property for locally convex spaces and topological groupsNov 09 2016We characterize Ascoli spaces by showing that a Tychonoff space $X$ is Ascoli iff the canonical map from the free locally convex space $L(X)$ over $X$ into $C_k\big( C_k(X)\big)$ is an embedding of locally convex spaces. We prove that an uncountable direct ... More
Quotient Equations and Integrals of Motion for Massive Spinor FieldMar 29 2003In this article a group-theoretical aspect of the method of dimensional reduction is presented. Then, on the base of symmetry analysis of an anisotropic space geometrical description of dimensional reduction of equation for massive spinor field is given. ... More
Soft wall model with inverse exponential profile as a model for the axial and pseudoscalar mesonsJul 11 2012According to the conjecture of the gauge/gravity duality a strongly coupled 4D field theory may be described by a dual 5D theory which is a free field theory in the first approximation. The usual description of the axial-vector sector in the bottom-up ... More
No-Wall Holographic Model for QCDDec 22 2010Mar 03 2011We propose a new type of bottom-up holographic model describing the Regge like spectrum of mesons. This type of spectrum emerges due to condensation of a scalar field in the bulk anti-de Sitter space. The gauge invariance of the action describing the ... More
Holographic like models as a five-dimensional rewriting of large-Nc QCDJan 18 2010Oct 13 2010The AdS/QCD models are known to be tightly related with the QCD sum rules in the large-Nc (called also planar) limit. Rewriting the theory of infinite tower of free stable mesons expected in the large-Nc QCD as a five-dimensional theory we scrutinize ... More
About the possibility of five-dimensional effective theories for low-energy QCDMar 18 2009The AdS/QCD models suggest an interesting idea that the effective theory of low-energy QCD may be formulated as a 5-dimensional field theory in the weak coupling regime in which the fifth coordinate plays a role of inverse energy scale. Taking the point ... More
A five-dimensional toy-model for light hadron excitationsAug 04 2009Jun 17 2010In the usual holographic approach to QCD, the meson spectrum is generated due to a non-trivial 5-dimensional background. We propose an alternative 5-dimensional scenario in which the spectrum emerges due to coupling to a scalar field whose condensation ... More
Properties of new unflavored mesons below 2.4 GeVJul 05 2007The global features of spectrum of highly excited light nonstrange mesons can be well understood within both chiral symmetry restoration scenario combined with the relation $M^2\sim J+n$ and within nonrelativistic description based on the relation $M^2\sim ... More
Saunders Mac Lane, the Knight of MathematicsJul 11 2005This is a short obituary of Saunders Mac Lane (1909--2005).