Multipole Structure Research Articles

Development of an M6.4 Circular Solar Flare According to the Observations in the Нα Line

The development of the 3N/M6.4 flare on July 19, 2000, in the active region NOAA 9087 was studied based on the analysis of its images in the Нα line. Нα filtergrams obtained at the Meudon Observatory were used. The flare-active region NOAA 9087 had a complex multipolar magnetic field structure. The flare of 3N/M6.4 class began with the appearance of two bright kernels near a large spot. A few minutes later, flare kernels appeared in the central part of the active region, where a coronal source of hard X-ray radiation was identified. The flare lasted 2.5 h. Its energy was released sequentially in different places of the active region. The flare kernels were located along the polarity inversion line at the boundaries of the chromospheric cells. The flare ribbons had a circular shape. An assumption is made about the magnetic topology of the fan-spine type containing a null point. In this case, flare ribbons are the intersections of the fan quasi-separatrix layer with the lower atmosphere. The successive appearance of flare kernels may indicate a slipping magnetic reconnection in the flare. The Нα images in the main phase of the flare show reconnecting loops in the eastern part of the active region that are clearly visible in the ultraviolet wavelength range.

THE OUTLOOK ON THE TURKEY’S FOREIGN POLICY FROM DIFFERENT PARADIGMS OF INTERNATIONAL RELATIONS

The article is attempt to evaluate the foreign policy of Turkey from the key paradigms of international relations: liberalism, constructivism, realism, neorealism and neoclassical realism. Turkish military power actively involved in Syria, Iraq, Libya, the Eastern Mediterranean, the South Caucasus with the intention to alter the existing power distribution. This may be considered as signs of the offensive realism strategy. Offensive realism asserts that states willing to use force to advance their own interests, and the survival in the international system requires to maximize power. Defensive neorealism holds that aggressive expansion collides with the interests of other states and their desire to ensure their own security in the first place. According to the balance of power theory, the expansion and maximization of power reduces the security of an offensive state by countering a coalition of balancing states. But in the case of Turkey, there are no signs of emerging a counterbalance coalition, and this is «know-how» of Erdogan’s policy. From the liberal perspective, also, there are no signs of countering of the internal and external liberal determinants (Turkish civil society, NATO’s policy, affairs with liberal allies) of Turkey’s foreign policy. The deadlock of joining Turkey to the EU and abolition of Ataturk’s secular and republican guidelines are signs of failure of liberal approach to Erdogan’s foreign policy. Turkey’s offensive policy, ignited nostalgia for the Ottoman Empire, means the inability of international institutional cooperation to overcome anarchy and power maximizing instinct. From the constructivist perspective, the social structure affects the decision- making process. And this is confirmed in Turkey. Expansionism and resentment of historical injustice towards Turkey are necessary to strengthen Erdogan’s power and legitimize it. Constructivist approach may explain the meaning Turkish, Turkic and Neo- Ottoman identities. Identities and interests mutually constitute and effect foreign- policy behavior. And Erdogan shapes identities in the state and beyond on the basis of the interests of the of the power. Neoclassical realism approach may be useful in the analysis of Turkish foreign policy too. It underlines importance of a state’s domestic arrangements, particularly decisionmakers’ perceptions. And, of course, Erdogan’s perception is crucial for foreign policy. Perceptions usually tend to follow the actual distribution of power, but in the case of Erdogan’s aggressive policy, there is a risk of misjudgment, when long-term trends are hidden behind short-term perceptions. The main emphasis of article is on attempts to determine Erdogan’s strategy and examine it from the standpoint of offensive (realism) / defensive (neoralism) approach of international relations, and evaluate its effectiveness. Erdogan has created a multipolar balancing structure of foreign relations, in which Turkish rivals restrain each other. This structure is similar to a pentahedron with Turkey in the center and its main rivals- partners on the tops. Erdogan, shifting closer to one top or another one, can effectively bargain using threats with other rivals.

The multipolar structure of fuzzballs

We extend and refine a general method to extract the multipole moments of arbitrary stationary spacetimes and apply it to the study of a large family of regular horizonless solutions to mathcal{N} = 2 four-dimensional supergravity coupled to four Abelian gauge fields. These microstate geometries can carry angular momentum and have a much richer multipolar structure than the Kerr black hole. In particular they break the axial and equatorial symmetry, giving rise to a large number of nontrivial multipole moments. After studying some analytical examples, we explore the four-dimensional parameter space of this family with a statistical analysis. We find that microstate mass and spin multipole moments are typically (but not always) larger that those of a Kerr black hole with the same mass and angular momentum. Furthermore, we find numerical evidence that some invariants associated with the (dimensionless) moments of these microstates grow monotonically with the microstate size and display a global minimum at the black-hole limit, obtained when all centers collide. Our analysis is relevant in the context of measurements of the multipole moments of dark compact objects with electromagnetic and gravitational-wave probes, and for observational tests to distinguish fuzzballs from classical black holes.

Multipole moments of compact objects with NUT charge: Theoretical and observational implications

We derive the multipole moments of the Kerr-NUT black hole spacetime using the Geroch-Hansen formalism, even though the spacetime is not asymptotically flat. Intriguingly, in the presence of the NUT charge, the absence of reflection symmetry about the equatorial plane, leads to mass and spin multipole moments of all orders, in stark contrast to Kerr-like spacetimes. This leads to a drastic departure of the multipolar structure of a compact object with NUT charge, whose implications for gravitational wave observations have been explored. Our analysis of multipole moments for the Kerr-NUT spacetime is also in tune with the Thorne's approach.

Multipolar boson stars: Macroscopic Bose-Einstein condensates akin to hydrogen orbitals

Boson stars are often described as macroscopic Bose-Einstein condensates. By accommodating large numbers of bosons in the same quantum state, they materialize macroscopically the intangible probability density cloud of a single particle in the quantum world. We take this interpretation of boson stars one step further. We show, by explicitly constructing the fully non-linear solutions, that static (in terms of their spacetime metric, gμν) boson stars, composed of a single complex scalar field, Φ, can have a non-trivial multipolar structure, yielding the same morphologies for their energy density as those that elementary hydrogen atomic orbitals have for their probability density. This provides a close analogy between the elementary solutions of the non-linear Einstein–Klein-Gordon theory, denoted Φ(N,ℓ,m), which could be realized in the macrocosmos, and those of the linear Schrödinger equation in a Coulomb potential, denoted Ψ(N,ℓ,m), that describe the microcosmos. In both cases, the solutions are classified by a triplet of quantum numbers (N,ℓ,m). In the gravitational theory, multipolar boson stars can be interpreted as individual bosonic lumps in equilibrium; remarkably, the (generic) solutions with m≠0 describe gravitating solitons [gμν,Φ(N,ℓ,m)] without any continuous symmetries. Multipolar boson stars analogue to hybrid orbitals is also constructed.

Sino-Russian Role in the 21st Century World Order

China and Russia have developed an underlying empathy on the transition of the contemporary US-led hegemonic world order. Since the dawn of the 21st century, the two Eurasian powers have been striving for transforming the global system to a multipolar world system. As Beijing and Moscow, along with other emerging powers were already weary of Washington’s unipolar moment and its self-proclaimed authority of overriding the entire international system. In the American worldwide hegemony, the rest of the nations; neither alone nor collectively could challenge its supremacy; as the political, economic and military dominance of the US was ascertained by its ascendency in the post-World war II established international organizations. However, during the past few decades the rapid rise of China; the resurgence of Russia and the relative decline of the US; evidently specify that the era of Pax-American is on the go. Moreover, the launching of Beijing sponsored transnational initiatives can be acknowledged as the pillars of a new multicentric global system in future. Hence, the dynamics of international politics are apparently heading towards the transition of the contemporary world system to a multipolar structure; where besides the US, China and Russia would also play significant role.

Distinguishing Fuzzballs from Black Holes through Their Multipolar Structure.

Within general relativity, the unique stationary solution of an isolated black hole is the Kerr spacetime, which has a peculiar multipolar structure depending only on its mass and spin. We develop a general method to extract the multipole moments of arbitrary stationary spacetimes and apply it to a large family of horizonless microstate geometries. The latter can break the axial and equatorial symmetry of the Kerr metric and have a much richer multipolar structure, which provides a portal to constrain fuzzball models phenomenologically. We find numerical evidence that all multipole moments are typically larger (in absolute value) than those of a Kerr black hole with the same mass and spin. Current measurements of the quadrupole moment of black-hole candidates could place only mild constraints on fuzzballs, while future gravitational-wave detections of extreme mass-ratio inspirals with the space mission LISA will improve these bounds by orders of magnitude.

On uniqueness of static asymptotically anti-de Sitter black hole

In this paper, the asymptotically anti-de Sitter spacetime with a hypersurface orthogonal Killing vector field is discussed near the conformal boundary by using Newman–Penrose formalism. We first investigate the multipole structure of a static, asymptotically anti-de Sitter spacetime. We note that, different to asymptotically flat case in which the multipoles are contained in , the multipoles of a static, asymptotically anti-de Sitter spacetime are all contained in . We then show that the Schwarzschild anti-de Sitter spacetime is the only asymptotically anti-de Sitter, vacuum, static, axisymmetric, type-D analytic solution of vacuum Einstein equation with a negative cosmological constant in a Bondi coordinate neighborhood of the conformal boundary if the spherical harmonic expansion of is finite.

« Perspectives »

This article draws the attention firstly on the diffusion of macro-regional organizations in each continent as well as on the inter-regional relations. Secondly it places this intermediary levels of governance - between states and global organizations - in the context of the big challenge of the interpretation of the current global order change after 1991.On the basis of a sophisticated conceptualization of both regionalism and inter-regionalism the articles addresses the impact of the multipolar power structure of the world, on regional cooperation. Two alternative scenarios are forecasted as outcome of this comparative research: either an instrumental and authoritarian downgrading of regional cooperation as influence spheres of great powers or the gradual emergence of a new multilateralism, post-hegemonic multilayered, more legitimate and more efficient.

Observations of GRO J1744–28 in quiescence with XMM-Newton

We report on the deep observations of the “bursting pulsar” GRO J1744–28, which were performed with XMM-Newton and aimed to clarify the origin of its X-ray emission in quiescence. We detect the source at a luminosity level of ∼1034 erg s−1 with an X-ray spectrum that is consistent with the power law, blackbody, or accretion-heated neutron star atmosphere models. The improved X-ray localization of the source allowed us to confirm the previously identified candidate optical counterpart as a relatively massive G/K III star at 8 kpc close to the Galactic center, implying an almost face-on view of the binary system. Although we could only find a nonrestricting upper limit on the pulsed fraction of ∼20%, the observed hard X-ray spectrum and strong long-term variability of the X-ray flux suggest that the source is also still accreting when not in outburst. The luminosity corresponding to the onset of centrifugal inhibition of accretion is thus estimated to be at least two orders of magnitude lower than previously reported. We discuss this finding in the context of previous studies and argue that the results indicate a multipole structure in the magnetic field with the first dipole term of ∼1010 G, which is much lower than previously assumed.

Braking indices of young radio pulsars: theoretical perspective

ABSTRACT Recently, Parthsarathy et al. analysed long-term timing observations of 85 young radio pulsars. They found that 15 objects have absolute values of braking indices ranging ∼10–3000, far from the classical value n = 3. They also noted a mild correlation between measured value of n and characteristic age of a radio pulsar. In this article, we systematically analyse possible physical origin of large braking indices. We find that a small fraction of these measurements could be caused by gravitational acceleration from an unseen ultra-wide companion of a pulsar or by precession. Remaining braking indices cannot be explained neither by pulsar obliquity angle evolution, nor by complex high-order multipole structure of the poloidal magnetic field. The most plausible explanation is a decay of the poloidal dipole magnetic field which operates on a time-scale ∼104−105 yr in some young objects, but has significantly longer time-scale in other radio pulsars. This decay can explain both amplitude of measured n and some correlation between n and characteristic age. The decay can be caused by either enhanced crystal impurities in the crust of some isolated radio pulsars or, more likely, by enhanced resistivity related to electron scattering off phonons due to slow cooling of low-mass neutron stars. If this effect is indeed the main cause of the rapid magnetic field decay manifesting as large braking indices, we predict that pulsars with large braking indices are hotter in comparison to those with n ≈ 3.

Axisymmetric deformations of neutron stars and gravitational-wave astronomy

Einstein's theory of general relativity predicts that the only stationary configuration of an isolated black hole is the Kerr spacetime, which has a unique multipolar structure and a spherical shape when non-spinning. This is in striking contrast to the case of other self-gravitating objects, which instead can in principle have arbitrary deformations even in the static case. Here we develop a general perturbative framework to construct stationary stars with small axisymmetric deformations, and study explicitly compact stars with an intrinsic quadrupole moment. The latter can be sustained, for instance, by crust stresses or strong magnetic fields. While our framework is general, we focus on quadrupolar deformations of neutron stars induced by an anisotropic crust, which continuously connect to spherical neutron stars in the isotropic limit. Deformed neutron stars might provide a more accurate description for stellar remnants formed in supernovae and in binary mergers, and can be used to improve constraints on the neutron-star equation of state through gravitational-wave detections and through the observation of low-mass X-ray binaries. We argue that, if the (dimensionless) intrinsic quadrupole moment is of a few percent or higher, the effect of the deformation is stronger than that of tidal interactions in coalescing neutron-star binaries, and might also significantly affect the electromagnetic signal from accreting neutron stars.

Exploring the physicochemical and morphological properties of peptide‐hybridized dendrimers (DendriPeps) and their aggregates

AbstractThis article presents an integrated experimental and computational study of DendriPeps, a novel class of dendrimers featuring a polyamidoamine (PAMAM) backbone hybridized with peptide segments. Hydroxyl‐terminated Generation 2 (G.2) DendriPeps, comprising either four lysines (Lys) or four glutamic acids (Glu), and G.3 DendriPeps, comprising 8 Lys or 8 Glu, were first characterized in terms of hydrodynamic radius (Rh) and ζ‐potential in aqueous solution. Unlike PAMAM dendrimers, DendriPeps form aggregates with Rh between 60 and 980 nm and ζ‐potential between −130 and 80 mV despite their strong net charge. Upon application of shear, all aggregates disassemble into monomeric DendriPeps (Rh ~ 1–3 nm), but reform rapidly as shear is removed. Rheological characterization confirmed that DendriPep aggregates are disrupted by mild shear, but reform reversibly. Molecular dynamics simulations, informed by titrimetry, suggest that DendriPep aggregation derives from their multipolar structure and ability to rearrange the intermolecular/intramolecular pairing of titratable moieties at different pH values.

The Northern forum as a successful model for the implementation of the identity of intra-state actors in the Arctic region

The process of transforming international relations goes on under the influence of globalization mechanisms together with the development of integration processes. The establishment of more complex and at the same time simple mechanisms of cooperation in the system of international relations between its actors is the result of a change in the methods of introducing cases. Moving away from the classical principles of cooperation-diplomatic contacts, alliances, the world ceases to be a bipolar system of world device, thanks to the process of globalization, a multipolar world structure is being built with the new actors inherent in the globalization process, gives an example of multinational corporations and NGOs. Under the influence of globalization, the usual tools of international politics are being modified, since within the framework of the new system of transnational interaction, national states are forced to adapt to a changing, interconnected and interdependent world in which there is no longer a clear division between external and internal affairs. State power is forced to transform, transferring to a larger extent part of its functions to supranational structures, sharing its administrative functions with these structures and creating new models of world political governance. The Northern Forum acts as an organization uniting the regions of the subjects for solving common problems in the Arctic region.

On the Magnetic Nature of an Exploding Granule as Revealed by Sunrise/IMaX

Abstract We study the photospheric evolution of an exploding granule observed in the quiet Sun at high spatial (∼0.″3) and temporal (31.5 s) resolution by the imaging magnetograph Sunrise/IMaX in 2009 June. These observations show that the exploding granule is cospatial to a magnetic flux emergence event occurring at mesogranular scale (up to ∼12 Mm2 area). Using a modified version of the SIR code for inverting the IMaX spectropolarimetric measurements, we obtain information about the magnetic configuration of this photospheric feature. In particular, we find evidence of highly inclined emerging fields in the structure, carrying a magnetic flux content up to ∼4 × 1018 Mx. The balance between gas and magnetic pressure in the region of flux emergence, compared with a very quiet region of the Sun, indicates that the additional pressure carried by the emerging flux increases the total pressure by about 5% and appears to allow the granulation to be modified, as predicted by numerical simulations. The overall characteristics suggest that a multipolar structure emerges into the photosphere, resembling an almost horizontal flux sheet. This seems to be associated with exploding granules. Finally, we discuss the origin of such flux emergence events.

Magnetic field configurations in neutron stars from MHD simulations

ABSTRACT We have studied numerically the evolution of magnetic fields in barotropic neutron stars, by performing non-linear magnetohydrodynamical simulations with the code pluto. For both initially predominantly poloidal and toroidal fields, with varying strengths, we find that the field settles down to a mixed poloidal–toroidal configuration, where the toroidal component contributes between ${\rm 10}$ and $20 {{\ \rm per\ cent}}$ of the total magnetic energy. This is, however, not a strict equilibrium, as the instability leads to the development of turbulence, which, in turn, gives rise to an inverse helicity cascade, which determines the final ‘twisted torus’ setup. The final field configuration is thus dictated by the non-linear saturation of the instability, and is not stationary. The average energy of the poloidal and toroidal components, however, is approximately stable in our simulations, and a complex multipolar structure emerges at the surface, while the magnetic field is dipolar at the exterior boundary, outside the star.

Compact Planar Multipole Antenna for Scalable Wide Beamwidth and Bandwidth Characteristics

This article proposes a concept of compact planar multipole antenna configured by multiple magnetic and electric dipoles as a single radiation element with a single signal excitation port. The proposed structure uses diverse orientations in magnetic field and electric coupling through segmented radiation conductors and ground vias. The uniqueness of multipole antenna can be emphasized by its compactness, wide beamwidth in both the E- and H-planes with a finite ground plane size, and wide impedance bandwidth characteristics. To verify the concept of multipole structure, four different types of antennas are proposed and analyzed. With a radiation element size of $0.33\lambda _{\mathrm {o}}\,\, \times 0.33\lambda _{\mathrm {o}}$ ( $\lambda _{\mathrm {o}}$ for free-space wavelength) and a finite ground size of $1.1\lambda _{\mathrm {o}}\,\, \times 1.1\lambda _{\mathrm {o}}$ at 5.9 GHz, the half-power beamwidths (HPBWs) of 175° and 133° in both the E- and H-planes were measured, respectively. A wider bandwidth characteristic compared to previously reported wide beamwidth planar antennas was also achieved by one of the proposed structures. The measured 10 dB impedance bandwidth was about 13% with HPBWs of 111° and 160° in both the E- and H-planes, respectively. Also, the measured peak gains were better than 5.3 dBi for all structures with an excellent gain flatness at the operation band.

Crystal Field Rotational Invariants: A New Light on the Crystal Field Effects

Two types of rotational invariants related to the crystal field (CF) Hamiltonian parameters are exploited: three multipolar CF strengths , , and of the second order and nine invariants of the third order. They determine correspondingly the next generation of the CF invariants, i.e., the second and the third CF splitting moments of any electronic state . The analytical formulas are assembled for the third CF splitting moment in the case of higher symmetry, 24 out of 32 central ion point symmetry groups. Due to the multipolar additivity of the second CF splitting moment, its formula is irrespective of the central ion point symmetry. Comparing the calculated CF splitting moments with the experimental ones is a valuable source of independent relationships among the involved CF parameters. The second CF splitting moments allow to preparameterize the CF Hamiltonian based on the , , and invariants. This reveals the actual multipolar structure of . While only two independent second moments are available, a method to obtain the possible variation ranges of the multipolar is given. In addition, the CF invariants provide an insight into the total CF splitting variation ranges under various unimodular .

Multihub – point of increase in Samara agglomeration- conurbation spatial development

The article deals with the theoretical position of the newly created environment for the functioning of transport and logistic services. The main purpose is to research the formation and functioning of multimodal transport and logistic hubs (Multihub). There were considered the practical issues connected with the realization of big investment projects of logistic infrastructure development that are inclined to local and international transport corridor. There are suggested the possible ways to place Multihubs in promising «points of increase» which are planned to be at the contact points of the peripheral Samara agglomeration-conurbation suburban belt with local rural settlement systems in order to include the Samara gubernia in the structure of the currently planned international transport corridors Europe - America and the Arctic – Southwestern Asia. The author of this article was tasked to explain the principles of phased development for the near, medium and long-term perspective of Volga region transport and communication framework. Currently, there are strong centripetal trends of movement from rural settlement systems to subcentres of Samara agglomeration. The developed approach contributes to the development of a multipolar multifunctional region structure. It will regulate the multidimensional field of social and functional spatial processes will provide conditions to increase the consumer and investment territory attractiveness that provide the effective use of land and socialization of the urban community.

Newtonian analogue of a Kerr black hole

A 250-year old Newtonian problem, first studied by Euler, turns out to share a lot of similarities with the most extreme astrophysical relativistic object, the Kerr black hole. Although the framework behind the two fields is completely different, both problems are related to gravitational fields that have quite intriguing analogies with respect to orbital motions of a test-body in them. The fundamental reason responsible for their extraordinary similarity is the integrability of both problems, as well as their common multipolar structure. In this paper we demonstrate the existence of a multitude of either qualitative, and sometimes quantitative, similarities between the two problems. Based on this analogy, one could use the Newtonian problem to get insight in cases where the relativistic treatment of the field of a Kerr black hole becomes quite complicated.