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At least 1,423 records · Page 79
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Nonlinear propagation of coherent electromagnetic waves in a dense magnetized plasma

We present an investigation of the nonlinear propagation of high-frequency coherent electromagnetic waves in a uniform quantum magnetoplasma. Specifically, we consider nonlinear couplings of right-hand circularly polarized electromagnetic-electron-cyclotron (CPEM-EC) waves with dispersive shear Alfven (DSA) and dispersive compressional Alfven (DCA) perturbations in plasmas composed of degenerate electron fluids and non-degenerate ion fluids. Such interactions lead to amplitude modulation of the CPEM-EC wave packets, the dynamics of which is governed by a three-dimensional nonlinear Schroedinger equation (NLSE) with the frequency shift arising from the relativistic electron mass increase in the CPEM-EC fields and density perturbations associated with the DSA and DCA perturbations. Accounting for the electromagnetic and quantum forces, we derive the evolution equation for the DSA and DCA waves in the presence of the magnetic field-aligned ponderomotive force of the CPEM-EC waves. The NLSE and the driven DSA and DCA equations are then used to investigate the modulational instability. The relevance of our investigation to laser-plasma interaction experiments and the cores of white dwarf stars is pointed out.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

First-principles investigation of uranium mononitride (UN): Effect of magnetic ordering, spin-orbit interactions and exchange correlation functional

Uranium mononitride (UN) is a promising nuclear fuel that combines the advantageous properties of readily used UO 2 and uranium alloys. Various properties of UN have been previously studied using different density functional theory (DFT) methodologies; however, there are still inconsistencies when it comes to the dynamical stability and defect properties of UN. We address these inconsistencies by studying the UN phonons and defect properties using DFT calculations employing two generalized gradient approximation (GGA) exchange-correlation functionals: PBE and AM05, with and without an added on-site Coulomb repulsion term (+U). Furthermore, we investigate the importance of spin-orbit coupling (SOC) when calculating the properties of UN. We use the different methodologies to determine the preference of UN to have antiferromagnetic (AFM) ordering, as seen in experiments, or ferromagnetic (FM) ordering of the uranium spins. We compare the crystallographic properties, density of states, the DFT X-ray photoelectron spectra and phonon dispersions calculated using the different methodologies. We demonstrate that GGA + U reproduces the AFM ordering in UN, but the crystal structure is dynamically unstable. We also show that magnetic ordering is important in finding the lowest energy defective structure, and that SOC has a distinct influence on the energy of the different uranium interstitial defects. Lastly, we discuss the point defect formation energies under U-rich and N-rich conditions, and the stoichiometric formation energies calculated with the different methodologies, providing insight into the observed tendency for forming hypostoichiometric UN.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Magnetically propagating Hund’s exciton in van der Waals antiferromagnet NiPS3

Abstract Magnetic van der Waals (vdW) materials have opened new frontiers for realizing novel many-body phenomena. Recently NiPS 3 has received intense interest since it hosts an excitonic quasiparticle whose properties appear to be intimately linked to the magnetic state of the lattice. Despite extensive studies, the electronic character, mobility, and magnetic interactions of the exciton remain unresolved. Here we address these issues by measuring NiPS 3 with ultra-high energy resolution resonant inelastic x-ray scattering (RIXS). We find that Hund’s exchange interactions are primarily responsible for the energy of formation of the exciton. Measuring the dispersion of the Hund’s exciton reveals that it propagates in a way that is analogous to a double-magnon. We trace this unique behavior to fundamental similarities between the NiPS 3 exciton hopping and spin exchange processes, underlining the unique magnetic characteristics of this novel quasiparticle.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Structure and magnetic properties of Ce₃(Ni/Al/Ga)₁₁—A new phase with the La₃Al₁₁ structure type

Single crystals of Ce₃(Ni/Al/Ga)₁₁ were obtained from an Al flux reaction. Single crystals of the title compound crystallizing in the orthorhombic space group Immm (No. 71, Z = 2) with a = 436.38(14), b = 1004.5(3) and c = 1293.4(4) pm. This is a standardized unit cell of the previously published La₃Al₁₁ structure type. Wavelength dispersive microprobe provides the composition of Ce₃.₁₁₍₁₎Ni₀.₀₃₍₁₎Al₈.₉₅₍₁₎Ga₁.₉₀₍₁₎. Single crystal refinement provides the composition Ce₃Ni₀.₀₈Al₉.₁₃Ga₁.₇₈ with substitution of the Ni and Ga on the Al1 and Al4 sites with the Al2 and Al3 solely occupied by Al. Magnetic susceptibility measurements reveal antiferromagnetic ordering with T N = 4.8 K and there is no evidence for a ferromagnetic ordering that has been reported for Ce₃Al₁₁. The effective magnetic moment was found to be μ eff = 1.9μB/Ce, which is lower than the expected value for trivalent Ce (2.54μB/Ce).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Syntheses, and crystal and electronic structures of the new Zintl phases Na{sub 2}ACdSb{sub 2} and K{sub 2}ACdSb{sub 2} (A=Ca, Sr, Ba, Eu, Yb): Structural relationship with Yb{sub 2}CdSb{sub 2} and the solid solutions Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} and Eu{sub 2-x}Yb{sub x}CdSb{sub 2}

Presented are the details of the syntheses, crystal and electronic structures of a new family of Zintl phases Na{sub 2}ACdSb{sub 2} and K{sub 2}ACdSb{sub 2} (A=Ca, Sr, Ba, Eu, Yb), as well as the solid solutions Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} and Eu{sub 2-x}Yb{sub x}CdSb{sub 2}. The structures of Na{sub 2}ACdSb{sub 2} and K{sub 2}ACdSb{sub 2} (A=Ca, Sr, Ba, Eu, Yb) were determined to be of a new type with the non-centrosymmetric space group Pmc2{sub 1} (no. 26), Pearson symbol oP12, with lattice parameters a=4.684(1)-4.788(1) A; b=9.099(3)-9.117(2) A; c=7.837(1)-8.057(2) A for the Na{sub 2}ACdSb{sub 2} series, and a=4.6637(9)-5.0368(8) A; b=9.100(2)-9.8183(15) A; and c=7.7954(15)-8.4924(13) A for K{sub 2}ACdSb{sub 2}, respectively. The solid solutions Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} and Eu{sub 2-x}Yb{sub x}CdSb{sub 2} (x{approx}1) are isostructural and isoelectronic to the recently reported Yb{sub 2}CdSb{sub 2} (space group Cmc2{sub 1} (no. 36), Pearson symbol cP20). All discussed structures are based upon CdSb{sub 2}{sup 4-} polyanionic layers, similar to the ones observed in Yb{sub 2}CdSb{sub 2}, with various alkali- and/or alkaline-earth cations coordinated to them. Magnetic susceptibility and Seebeck coefficient measurements on selected Eu{sub 2-x}Yb{sub x}CdSb{sub 2} samples, taken at low temperatures up to 300 K, are also reported. -- Graphical abstract: The quaternary Zintl phases Na{sub 2}ACdSb{sub 2} and K{sub 2}ACdSb{sub 2} (A=Ca, Sr, Ba, Eu, Yb) with novel layered structures have been synthesized for the first time and structurally characterized by single-crystal X-ray diffraction. Reported as well are the results from crystallographic and property studies of the closely related solid solutions Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} (x{approx}1), and Eu{sub 2-x}Yb{sub x}CdSb{sub 2} (1<x{<=}2). Display Omitted Research highlights: {yields} Na{sub 2}ACdSb{sub 2} and K{sub 2}ACdSb{sub 2} (A=Ca, Sr, Ba, Eu, Yb) are new quaternary Zintl phases. {yields} Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} (x{approx}1), and Eu{sub 2-x}Yb{sub x}CdSb{sub 2} (1<x<2) are solid solutions. {yields} Both structures are layered, based on corner-shared CdSb{sub 4} tetrahedra. {yields} Eu{sub 2-x}Yb{sub x}CdSb{sub 2} (1<x<2) exhibit high Seebeck coefficient (217 {mu}V/K at RT).

36 MATERIALS SCIENCE↗
DOE OSTI2011

NSLS-II X-Ray Diagnostics Development

NSLS-II x-ray diagnostics will provide continuous online data of electron beam dimensions, which will be used to derive electron beam emittance and energy spread. It will also provide information of electron beam tilt for coupling evaluation. X-ray diagnostics will be based on imaging of bending magnet and three-pole wiggler synchrotron radiation sources. Diagnostics from three-pole wiggler source will be used to derive particles energy spread. Beta and dispersion functions will have to be evaluated for emittance and particles energy spread calculations. Due to small vertical source sizes imaging need to be performed in x-ray energy range. X-ray optics with high numerical aperture, such as compound refractive lens, will be used to achieve required spatial resolution. Optical setups with different magnifications in horizontal and vertical directions fill be employed to deal with large aspect ratio of the source. X-ray diagnostics setup will include x-ray imaging optics, monochromatization, x-ray imaging and recording components.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

A Massive Prestellar Clump Hosting No High-mass Cores

The infrared dark cloud (IRDC) G028.23-00.19 hosts a massive (1500 M {sub ⊙}), cold (12 K), and 3.6–70 μ m IR dark clump (MM1) that has the potential to form high-mass stars. We observed this prestellar clump candidate with the Submillimeter Array (∼3.″5 resolution) and Jansky Very Large Array (∼2.″1 resolution) in order to characterize the early stages of high-mass star formation and to constrain theoretical models. Dust emission at 1.3 mm wavelength reveals five cores with masses ≤15 M {sub ⊙}. None of the cores currently have the mass reservoir to form a high-mass star in the prestellar phase. If the MM1 clump will ultimately form high-mass stars, its embedded cores must gather a significant amount of additional mass over time. No molecular outflows are detected in the CO (2-1) and SiO (5-4) transitions, suggesting that the SMA cores are starless. By using the NH{sub 3} (1, 1) line, the velocity dispersion of the gas is determined to be transonic or mildly supersonic (Δ V {sub nt}/Δ V {sub th} ∼ 1.1–1.8). The cores are not highly supersonic as some theories of high-mass star formation predict. The embedded cores are four to seven times more massive than the clump thermal Jeans mass and the most massive core (SMA1) is nine times less massive than the clump turbulent Jeans mass. These values indicate that neither thermal pressure nor turbulent pressure dominates the fragmentation of MM1. The low virial parameters of the cores (0.1–0.5) suggest that they are not in virial equilibrium, unless strong magnetic fields of ∼1–2 mG are present. We discuss high-mass star formation scenarios in a context based on IRDC G028.23-00.19, a study case believed to represent the initial fragmentation of molecular clouds that will form high-mass stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

FARADAY ROTATION: EFFECT OF MAGNETIC FIELD REVERSALS

The standard formula for the rotation measure (RM), which determines the position angle, {psi} = RM{lambda}{sup 2}, due to Faraday rotation, includes contributions only from the portions of the ray path where the natural modes of the plasma are circularly polarized. In small regions of the ray path where the projection of the magnetic field on the ray path reverses sign (called QT regions) the modes are nearly linearly polarized. The neglect of QT regions in estimating RM is not well justified at frequencies below a transition frequency where mode coupling changes from strong to weak. By integrating the polarization transfer equation across a QT region in the latter limit, I estimate the additional contribution {Delta}{psi} needed to correct this omission. In contrast with a result proposed by Broderick and Blandford, {Delta}{psi} is small and probably unobservable. I identify a new source of circular polarization, due to mode coupling in an asymmetric QT region. I also identify a new circular-polarization-dependent correction to the dispersion measure at low frequencies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

The Microscopic Magnetic Properties of W-type Hexaferrite Powder Prepared by A Sol-Gel Route

Magnetic particles of W-type barium-calcium hexaferrite (BaCa{sub 2}Fe{sub 16}O{sub 27}) have been synthesized using a Stearic acid gel route. The gel precursors were dried at 100 deg. C for 2 hrs and then calcinated at 650 deg. C, 750 deg. C, 850 deg. C and 950 deg. C for 4 hrs in a furnace and slowly cooled to room temperature in order to obtain barium-calcium hexaferrite particles. The microscopic magnetic properties of prepared samples studying using Moessbauer spectroscopy. Moessbauer spectra of all samples were recorded at room temperature. Mossbauer parameters like Isomer shift, Quadruple splitting etc. were calculated with respect to iron foil. Barium calcium hexaferrite samples heated at 650 deg. C, 750 deg. C, 850 deg. C show relaxation type Moessbauer spectra along with paramagnetic doublet. The intensity of paramagnetic doublet increases with temperature confirm the presence of ferrous ions in the samples, where as sample calcinated at 950 deg. C confirm the presence of ferrimagnetic phase with partial super paramagnetic nature of prepared hexaferrite sample.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Coherent structures and turbulent spectrum in solar wind plasmas

The present paper investigates the localization of a uniform plane kinetic Alfvén wave (KAW) due to the coupling with the density/magnetic field fluctuations associated with a magnetosonic wave propagating in the transverse direction, i.e., perpendicular to the background magnetic field. To gain the physical insight into this evolution, a simplified analytical model based on the Mathieu equation has also been studied. Numerical method has also been used to analyse the evolution of KAW. The magnetic fluctuation spectrum follows Kolmogorovian scaling above the proton gyroradius scalelength, which is regarded as the inertial range. Below this scale, a steepened spectrum has been obtained in the dispersive range with power law index ∼−2.5, which continues up to the dissipation range. Our results reveal that the proposed mechanism may be an interesting physical mechanism for transferring the energy from larger lengthscales to smaller lengthscales in the solar wind plasmas. Relevance of the present study with Cluster spacecraft observations has also been discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Pb{sub 5}Fe{sub 3}TiO{sub 11}Cl: A rare example of Ti(IV) in a square pyramidal oxygen coordination

A new oxychloride Pb{sub 5}Fe{sub 3}TiO{sub 11}Cl has been synthesized using the solid state method. Its crystal and magnetic structure was investigated in the 1.5–550 K temperature range using electron diffraction, high angle annular dark field scanning transmission electron microscopy, atomic resolution energy dispersive X-ray spectroscopy, neutron and X-ray powder diffraction. At room temperature Pb{sub 5}Fe{sub 3}TiO{sub 11}Cl crystallizes in the P4/mmm space group with the unit cell parameters a=3.91803(3) Å and c=19.3345(2) Å. Pb{sub 5}Fe{sub 3}TiO{sub 11}Cl is a new n=4 member of the oxychloride perovskite-based homologous series A{sub n+1}B{sub n}O{sub 3n−1}Cl. The structure is built of truncated Pb{sub 3}Fe{sub 3}TiO{sub 11} quadruple perovskite blocks separated by CsCl-type Pb{sub 2}Cl slabs. The perovskite blocks consist of two layers of (Fe,Ti)O{sub 6} octahedra sandwiched between two layers of (Fe,Ti)O{sub 5} square pyramids. The Ti{sup 4+} cations are preferentially located in the octahedral layers, however, the presence of a noticeable amount of Ti{sup 4+} in a five-fold coordination environment has been undoubtedly proven using neutron powder diffraction and atomic resolution compositional mapping. Pb{sub 5}Fe{sub 3}TiO{sub 11}Cl is antiferromagnetically ordered below 450(10) K. The ordered Fe magnetic moments at 1.5 K are 4.06(4) μ{sub B} and 3.86(5) μ{sub B} on the octahedral and square-pyramidal sites, respectively. - Highlights: • Pb{sub 5}Fe{sub 3}TiO{sub 11}Cl has been synthesized using the solid state method. • The structure has been refined using neutron powder diffraction data at 1.5–550 K. • It is a new n=4 member of the perovskite-related homologous series A{sub n+1}B{sub n}O{sub 3n−1}Cl. • Ti{sup 4+} cations have both octahedral and square-pyramidal coordination environment. • Pb{sub 5}Fe{sub 3}TiO{sub 11}Cl is antiferromagnetically ordered below T{sub N}≈450 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1997

Sounding of the Cleft Ion Fountain Energization Region

The objectives of the ground-based observations in support of the SCIFER are: Acquire and display ionospheric conditions prior to launch to aid in the establishment of launch criteria in real time. Observers at both stations participated in real-time visual interpretation. Solar wind data from IMP-8 and WIND were acquired and interpreted in real time. Telephonic and data links were established at the observatory for the launch window period. Ground-based observatory countdown and launch criteria were developed. 2) Relate optical and magnetic ionospheric signatures observed from the ground to magnetospheric boundaries in the energetic particle flux measured at the payload. The energetic electron trapping boundary was found to correspond to the equatorward edge of the discrete auroral arcs forming the dayside aurora. The energetic electron trapping boundary was found to correspond to the poleward edge of pulsating aurora. The pulsating aurora was found to correspond to one second bursts of energy-dispersed electrons originating in the equatorial plane. Pulsations at larger intervals corresponded to travel times to the conjugate region and return. The pulsating aurora was also directly linked to the geomagnetic pulsations and traveling magnetic vortices, all occurring equatorward of the trapping boundary. 630 nm emission corresponding to less than 10 eV electron precipitation was observed equatorward of the trapping boundary (L=15) and ascribed to photoelectrons from the sunlit conjugate region. 3) Aid in the interpretation of time/space incongruities in the rocket data. The motion of the payload conjugate across the aurora showed that the payload passed over three distinct arc systems on the poleward side of the trapping boundary. These results were reported in a series of articles to be printed in Geophysical Research Letters on June 15, l996.

Kintner, P.↗
DOE OSTI2024

Inhibition of asphaltene aggregation using deep eutectic solvents: COSMO-RS calculations and experimental validation

Asphaltene precipitation/deposition adversely affects various oil and gas processes, such as oil recovery, transportation, and petroleum processing. The resulting increase in viscosity of crude oil decreases distillate yields creating unstable phase separation. Deep eutectic solvents (DESs) have recently gained interest as inhibitors of asphaltene aggregation. The goal of the present study is to derive the mechanism of inhibition of petroleum asphaltene aggregation by a novel screening of DESs. An archipelago-based chemical structure of asphaltene was adopted for performing quantum chemical calculations. The structure was used in the conductor-like screening model for real solvents (COSMO-RS) model to screen potential DESs for asphaltene precipitation. It was found that DESs containing thymol were the most promising of the 153 DES combinations screened. The COSMO-RS predictions were validated experimentally using solubility data of asphaltene in DESs. Among the studied DESs, thymol-diphenyl ether provided the highest solubility for asphaltene, which was further validated using the experimental and the COSMO-RS predicted data. In addition, to characterize the structural interactions between asphaltene and DESs, Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) measurements were performed. It was found that strong interaction between asphaltene and the DESs is responsible for the higher asphaltene dispersion. Finally, the present approach opens pathways to rationally design and understand the impact of structural variation of DESs based on their interactions with asphaltene.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Quantum gates controlled by spin chain soliton excitations

Propagation of soliton-like excitations along spin chains has been proposed as a possible way for transmitting both classical and quantum information between two distant parties with negligible dispersion and dissipation. In this work, a somewhat different use of solitons is considered. Solitons propagating along a spin chain realize an effective magnetic field, well localized in space and time, which can be exploited as a means to manipulate the state of an external spin (i.e., a qubit) that is weakly coupled to the chain. We have investigated different couplings between the qubit and the chain, as well as different soliton shapes, according to a Heisenberg chain model. It is found that symmetry properties strongly affect the effectiveness of the proposed scheme, and the most suitable setups for implementing single qubit quantum gates are singled out.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Magnonic band gaps in two-dimension magnonic crystals with diffuse interfaces

In this paper, the plane wave method is extended to include the diffuse interface in the calculation of the dispersion of spin waves in two-dimension magnonic crystals. The diffuse interfaces with linear and sinusoidal profiles of variation in the spontaneous magnetization and exchange constant are considered and the effects of the thicknesses and profiles of diffuse interfaces on the magnonic band gaps are investigated. The results show that the thicknesses and profiles of diffuse interfaces are clearly seen to play a significant role in determining the size and position of the magnonic band gaps in the both square and triangular lattices in the exchange interaction regime. The smooth (linear or sinusoidal) interface does not lead to disappearance of the band gaps, instead it may lead to larger band gaps than those in the model with sharp (infinitely thin) diffuse interface under certain conditions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Magnetic and electronic structures of antiferromagnetic topological material candidate EuMg 2 Bi 2

In this work, EuMg 2 Bi 2 has been investigated to understand the electronic and magnetic behaviors as an antiferromagnetic (AFM) topological semimetal candidate. High-quality single crystals of EuMg 2 Bi 2 were grown via a Bi flux and, subsequently, characterized to be consistent with the previously reported bulk magnetic and resistivity properties. A ferromagnetic interaction is indicated by the positive Curie–Weiss temperature obtained through fitting the bulk magnetic susceptibility data. The bulk resistivity measurements reveal an interesting electronic behavior that is potentially influenced by a competing antiferromagnetic and ferromagnetic interaction in and out of the ab plane. From the resulting refinement of the neutron diffraction data, EuMg 2 Bi 2 was found to exhibit an A-type magnetic structure with Eu 2+ moments ferromagnetically aligned in the plane and antiferromagnetically stacked between neighbor ferromagnetic Eu layers. The power law fitting magnetic ordering parameter below TN~8 K agrees with the 2D Heisenberg model, indicating a weak interlayer antiferromagnetic interaction. Considering the magnetic structure determined by neutron diffraction, the surface state calculation suggests that EuMg 2 Bi 2 is an AFM topological insulator candidate. Linearly dispersed Dirac surface states were also observed in our angle-resolved photoemission spectroscopy measurements, consistent with the calculation.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Multi-harmonic Rutherford island theory

Rutherford island theory, which governs the nonlinear evolution of tearing modes in tokamak plasmas, is generalized to take into account situations in which the conventional one-harmonic approximation is not valid. The analysis incorporates non-inductive currents driven by radio frequency (RF) electromagnetic waves injected into the plasma. A multi-harmonic tearing mode dispersion relation is derived that takes the form of a nonlinear inhomogeneous matrix eigenvalue problem. The dispersion relation is solved in the so-called two-harmonic approximation, in which only the principal Fourier harmonic of the perturbed magnetic flux and its first overtone are included in the calculation. In the absence of RF current drive, the nonlinear behavior of a tearing mode predicted in the two-harmonic approximation does not differ substantially from that predicted in the one-harmonic approximation. On the other hand, RF current drive that is sufficiently localized in the vicinity of the O-points of the mode's magnetic island chain is capable of triggering bifurcations of the O-points (which is impossible in the one-harmonic approximation). However, the current drive is incapable of triggering bifurcations of the island X-points. This finding is significant because Bardóczi and Evans recently observed bifurcations of magnetic island chain O-points in the presence of RF current drive in the DIII-D tokamak but did not observe bifurcations of the X-points. Finally, the changes in the topology of the magnetic island flux-surfaces induced by RF current drive are found to facilitate the stabilization of the tearing mode.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

TURBULENT PAIR DISPERSION OF PHOTOSPHERIC BRIGHT POINTS

Observations of solar granulation obtained with the New Solar Telescope of Big Bear Solar Observatory are used to study the turbulent pair dispersion of photospheric bright points in a quiet-Sun area, a coronal hole, and an active region plage. In all the three magnetic environments, it is found that the pair mean-squared separation {Delta}{sup 2}(t) follows a power-law timescaling {Delta}{sup 2}(t) {approx} t {sup {eta}} in the range 10 s {approx}< t {approx}< 400 s. The power-law index is found to be {eta} {approx_equal} 1.5 for all the three investigated regions. It is shown that these results can be explained in the same framework as the classical Batchelor theory, under the hypothesis that the observed range of timescales corresponds to a non-asymptotic regime in which the photospheric bright points keep the memory of their initial separations.

79 ASTRONOMY AND ASTROPHYSICS↗