Accumulation of magnetic field energy in an active region due to the alpha-effect

The problem of accumulation of magnetic field energy in an active region (AR) as the energy of electric currents in the AR atmosphere is not yet completely clear. Along with the commonly accepted concept of generation of electric current systems in an AR due to large- scale shearing motions at the photospheric level [1,2], another possibility of magnetic field energy accumulation has recently been proposed theoretically [3]. Assuming that the AR magnetic field evolves via a sequence of force- free configurations, Seehafer shows that the energy of small- scale field and velocity fluctuations can be transformed into that of large-scale current systems of an AR (alpha-effect). The necessary condition for the alpha-effect to exist is the presence of the sign- dominant current helicity H _c =B · (?×B) in the volume is considered. The purpose of this paper is to clarify the fulfillment of this condition in various ARs. Based on the measurements of magnetic field vector in 40 active regions of the maximum of the 22nd cycle we calculated the current helicity of the field B_z · (?×B) _z in the photosphere and obtained the following results. In 36 ARs we found a significant imbalance of the current helicity of the field (5 to 75%) such that in 33 ARs the excess of the current helicity was positive in the southern hemisphere and negative in the northern hemisphere. Therefore, in ARs the necessary condition for transfer of the energy of small-scale fluctuations of the field and velocity into the energy of large- scale electric currents in ARs is fulfilled rather frequently.     

Amplitudes with different helicity configurations of noncommutative QED

The amplitudes of purely photon processes of noncommutative QED (NCQED) are derived for different helicity configurations of photons. The basic ingredient is the NCQED counterpart of the Yang–Mills recursion relations by means of Berends and Giele. The explicit solutions of recursion relations for NCQED photon current with special helicity configurations and also recursion relations for the NCQED fermion–photon current with special helicity configurations of photons (all photons have plus helicity) are presented.     

Possible effect of solar activity on variation of the tree-rings of a 500 a platycladus orientalis at the Mausoleum of Emperor Huang

The variation of the tree-ring’s index of a platycladus orientalis at the Mausoleum of Emperor Huang and of a long series of sunspots relative number during AD1470–1974 are analyzed by using the wavelet power spectrum method, and their variation characters are also discussed. It is determined that the tree-ring’s variation has cycles of approximate 2–7, 11, 93 and 150 a. Two data series are used for analyzing sunspot relative number (SSN) variation. First, the analysis of the annual average SSN during AD1700–1974 proved that variation cycles are about 11, 50, and 93 a; then, the data during AD1465–1975 obtained from the decadal average SSN train over 7000 a reconstructed on the geomagnetic data is analyzed and its variation cycles are about 50, 90, and 160 a. Besides the tree-rings cycle of 2–7 a is commonly considered to be related to ENSO, while 11 a cycle is related to solar Schwabe cycle; in addition, it is possible that the cycles of 90 and150 a are likely to be related to solar Gleissberg cycle and Suess cycle. The correlations between them are possibly due to the effect of solar activity on the climate and additionally on the tree’s growth. Supported by the National Natural Science Foundation of China (Grant No. 19373017)     

Current helicity pattern of large-scale magnetic field on the photosphere

Following Pevtsov and Latushko, we study the current helicity pattern of the large-scale magnetic field on the photosphere. We use the same technique as theirs to derive the vector magnetic field (B _r , B _θ , B _ϕ ) from full-disk longitudinal magnetograms based on the assumption that large-scale magnetic fields evolve rather slowly and the variations of the longitudinal magnetic fields within certain time duration are caused by the changing position angles only. Different from their study, we have calculated the current helicity maps directly from the derived vector magnetograms, rather than from obtaining the latitudinal variation of h _c by ignoring the role of B _θ component and averaging B _r and B _ϕ over all solar longitudes. This approach significantly strengthens the evidence of the hemispheric rule presented in the reconstructed vector magnetic field. Our study shows that the established hemispheric sign rule, that is, positive helicity sign in the southern hemisphere and negative helicity sign in the northern hemisphere, is applicable everywhere in the global magnetic field, namely, also evident in weak fields outside active regions, and that the obtained sign pattern is independent of the longitudinal magnetograms and the parameters that we have used.     

The Origin of Short-Time Variations in Cosmic-Ray Intensity

It is well known today that a continuous stream of highly ionized plasma is emitted from the Sun’s surface. This plasma is called the solar wind and consists of protons, electrons, and light nuclei. The solar wind pushes the solar magnetic field into interplanetary space to form the interplanetary magnetic field. The interplanetary magnetic field is a dynamical system that depends on the solar cycle and the Sun’s rotation phase. Thus, the Solar System is a natural plasma physics laboratory with an enormous multitude of different effects showing the current state of the system. By recording cosmic-ray fluxes, one can study the behavior of the interplanetary magnetic field and obtain information about processes that occur both on the Sun’s surface and throughout the Solar System. The main short-time variations in cosmic-ray intensity include the 27-day variations and the Forbush decreases. These variations are caused by complex solar plasma structures, which are generated by different processes on the Sun’s surface and propagate through space in a wide range of velocities. Cosmic-ray fluxes recorded with the PAMELA magnetic spectrometer on board the Resurs DK1 satellite in 2006–2016 are used to show some examples of cosmic-ray variations.     

Dynamics of processes in active regions NOAA 6652 and 6654 on the sun

On the basis ofH _α filtergrams we study the compact active regions (ARs) NOAA 6652 and 6654 with a few spots characterized by an increased solar activity and geoefficiency. The variation of morphology of ARs is studied during their evolution. Ejection features and activization of filaments are analyzed along with the correlation of their behavior with the flare situation in an AR. The relation with the solar magnetic structures is established.     

The magnetic cycle in GCR intensity near the Earth: Phase of the intensity maximum in the negative half-period of the magnetic cycle

We discuss the behavior of GCR modulation-important heliospheric characteristics, along with the behavior of the intensity itself in the region of the Earth’s orbit in epochs of the minimum of the solar cycle (and the maximum of GCR intensity). Of special interest is the situation of the current anomalously prolonged and deep minimum of the 24th cycle. We investigate how the maximum GCR intensity in this cycle (which is substantially different for low and high energies) could be related to this same characteristic in previous normal minima of solar activity.     

Helicity generation in turbulent MHD flows

We study turbulent flow of a conducting liquid in a uniform external magnetic field. It is shown that intense helicity generation is possible in the presence of a mean shear flow. It is noted that even though the mean helicity of the initial flow can be zero, the presence of internal topological structure of the flow, for example the presence of helicity of different signs at different scales, is nevertheless necessary for helicity generation. Zh. éksp. Teor. Fiz. 114, 946–955 (September 1998)     

Lepton polarization asymmetry and forward–backward asymmetry in exclusive B→K<Subscript>1</Subscript>τ<Superscript>+</Superscript>τ<Superscript>-</Superscript> decay in universal extra dimension scenario

Decay rate, forward–backward asymmetry and polarization asymmetries of the final state leptons in B→K₁τ⁺τ^-, where K₁ is the axial vector meson, are calculated in the standard model and in the universal extra dimension (UED) model. The sensitivity of the observables to the compactification radius R, the only unknown parameter in the UED model, is studied. Finally, the helicity fractions of the final state K₁ are calculated and their dependence on the compactification radius is discussed. This analysis of the helicity fraction is briefly extended to B→K^*ℓ⁺ℓ^- (ℓ=e,μ) and compared with the other approaches existing in the literature.     

Influence of deposition conditions on the antireflection properties of diamond-like carbon films for Si-based solar cells

The influence of deposition conditions on the antireflection properties of diamond-like carbon films for Si-based solar cells is studied theoretically. The values of the short-circuit current density for Si solar cells covered by diamond-like carbon films deposited at different concentrations of nitrogen in the gas mixture are calculated and compared with the associated values for uncovered solar cells. It is shown that the short-circuit current density increases with nitrogen concentration in the gas mixture because of a lower light absorption by the growing film. Optimum thicknesses of the diamond-like carbon films are calculated that provides a maximal increase in the output short-circuit current density of Si-based solar cells under both AM1.5 and AM0 conditions. Published in Russian in Zhurnal Tekhnicheskoĭ Fiziki, 2006, Vol. 76, No. 5, pp. 122–126. The article was translated by the authors.     

Temporal changes in the energy spectrum of Forbush decreases in 20–23 solar activity cycles

Variations in the energy spectrum of galactic cosmic rays during Forbush decreases registered in the 20–23 solar activity cycles are studied, using the data from neutron monitors and the Yakutsk cosmic ray spectrograph. It is shown that the Forbush decreases in the 23rd cycle of solar activity had a harder energy spectrum than in the three previous cycles, due to the relatively low level of turbulence of the interplanetary magnetic field during the 23rd solar activity cycle.     

Radio interferometric observations of solar bursts in the decimeter range with millisecond temporal resolution

We describe the radio interferometric equipment for observation of solar spike-like events at decimeter wavelengths with millisecond time resolution. The equipment was tested using a two-element interferometer (2 RT7, f=540 MHz, baseline 416 m) at the “Staraya Pustyn” radioastronomical station (RAS) of the Radiophysical Research Institute of Nizhny Novgorod (NIRFI) in October–November 1993 and in September–October 1994. Over 20 solar bursts of different durations, which showed considerable interference response, were detected with time resolution 0.256 ms. The typical time variation scale of the bursts was from 50 to 200 ms. Bursts with time scales less than 20 ms were absent. The actual possibility of measuring the displacements of radio source brightness centers with accuracy up to 1–2 arc s is shown. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 9, pp. 1063–1072, September, 1997.     

Study of solar features causing GMSs with 250γ<<Emphasis Type="Italic">H</Emphasis><400γ

The effect of solar features on geospheric conditions leading to geomagnetic storms (GMSs) with planetary index,A ^P ≥ 20 and the range of horizontal component of the Earth’s magnetic fieldH such that 250γ <H < 400γ has been investigated using interplanetary magnetic field (IMF), solar wind plasma (SWP) and solar geophysical data (SGD) during the period 1978–99. Statistically, it is observed that maximum number of GMSs have occurred during the maximum solar activity years of 21st and 22nd solar cycles. A peculiar result has been observed during the years 1982, 1994 when sunspot numbers (SSNs) decrease very rapidly while numbers of GMSs increase. No distinct association between yearly occurrence of disturbed days and SSNs is observed. Maximum number of disturbed days have occurred during spring and rainy seasons showing a seasonal variation of disturbed days. No significant correlation between magnitude (intensity) of GMSs and importance ofH _α , X-ray solar flares has been observed. Maximum number of GMSs is associated with solar flares of lower importance, i.e., SF during the period 1978-93.H _α , X-ray solar flares occurred within lower helio-latitudes, i.e., (0–30)°N to (0–30)°S are associated with GMSs. NoH _α , X-ray solar flares have occurred beyond 40°N or 40°S in association with GMSs. In helio-latitude range (10–40)°N to (10–40)°S, the 89.5% concentration of active prominences and disappearing filaments (APDFs) are associated with GMSs. Maximum number of GMSs are associated with solar flares. Coronal mass ejections (CMEs) are related with eruptive prominences, solar flares, type IV radio burst and they occur at low helio-latitude. It is observed that CMEs related GMS events are not always associated with high speed solar wind streams (HSSWSs). In many individual events, the travel time between the explosion on the Sun and maximum activity lies between 58 and 118 h causing GMSs at the Earth.     

Hybrid polymer-CdS solar cell active layers formed by in situ growth of CdS nanoparticles

The integration of semiconductor nanoparticles (NPs) into a polymeric matrix has the potential to enhance the performance of polymer-based solar cells taking advantage of the physical properties of NPs and polymers. We synthesize a new class of CdS-NPs-based active layer employing a low-cost and low temperature route compatible with large-scale device manufacturing. Our approach is based on the controlled in situ thermal decomposition of a cadmium thiolate precursor in poly(3-hexylthiophene) (P3HT). The casted P3HT:precursor solid foils were heated up from 200 to 300 °C to allow the precursor decomposition and the CdS-NP formation within the polymer matrix. The CdS-NP growth was controlled by varying the annealing temperature. The polymer:precursor weight ratio was also varied to investigate the effects of increasing the NP volume fraction on the solar cell performances. The optical properties were studied by using UV–Vis absorption and photoluminescence (PL) spectroscopy at room temperature. To investigate the photocurrent response of P3HT:CdS nanocomposites, ITO/P3HT:CdS/Al solar cell devices were realized. We measured the external quantum efficiency (EQE) as a function of the wavelength. The photovoltaic response of the devices containing CdS-NPs showed a variation compared with the devices with P3HT only. By changing the annealing temperature the EQE is enhanced in the 400–600 nm spectral region. By increasing the NPs volume fraction remarkable changes in the EQE spectra were observed. The data are discussed also in relation to morphological features of the interfaces studied by Focused Ion Beam technique.     

Ion abundances of low-energy quiet period particle fluxes at 1 AU

The ion abundances of charged particle fluxes with energies of 0.032–1.28 MeV/nucleon during the quiet period of solar activity are investigated using spacecraft data. The values of Fe/O ratios obtained in 35 such periods in the 23rd solar cycle are compared with the mean ion abundances in the solar corona, in the gradual and impulsive solar energetic particle events, and in the solar wind. It is believed that coronal holes near the equator could be one of possible source of background low energy particle fluxes.     

Deviation from tri-bimaximal mixings through flavour twisters in inverted and normal hierarchical neutrino mass models

We explore a novel possibility for lowering the solar mixing angle (θ ₁₂) from tri-bimaximal mixings, without sacrificing the predictions of maximal atmospheric mixing angle (θ ₂₃ = 45°) and zero reactor angle (θ ₁₃ = 0°) in the inverted and normal hierarchical neutrino mass models having 2–3 symmetry. This can be done through the identification of a flavour twister term in the texture of neutrino mass matrix and the variation of such term leads to lowering of solar mixing angle. For the observed ranges of Δm ₂₁² and Δm ₂₃², we calculate the predictions on tan² θ ₁₂ = 0.5, 0.45, 0.35 for different input values of the parameters in the neutrino mass matrix. We also observe a possible transition from inverted hierarchical model having even CP parity (Type-IHA) to inverted hierarchical model having odd CP parity (Type-IHB) in the first two mass eigenvalues, when there is a change in input values of parameters in the same mass matrix. The present work differs from the conventional approaches for the deviations from tri-bimaximal mixing, where the 2–3 symmetry is broken, leading to θ ₂₃ ≠ 45° and θ ₁₃ ≠ 0°.      

Molecular dynamics simulation of thermal conductivity of Cu–Ar nanofluid using EAM potential for Cu–Cu interactions

Mechanism of heat conduction in copper-argon nanofluids is studied by molecular dynamics simulation and the thermal conductivity was obtained using the Green–Kubo method. While the interatomic potential between argon atoms is described using the well-known Lennard–Jones (L–J) potential, a more accurate embedded atom method (EAM) potential is used in describing the interatomic interaction between copper atoms. It is found that the heat current autocorrelation function obtained using L–J potential to describe the copper-copper interatomic interaction fluctuates periodically due to periodic oscillation of the instantaneous microscopic heat fluxes. Thermal conductivities of nanofluids using EAM potentials were calculated with different volume fractions but the same nanoparticle size. The results show that thermal conductivity of nanofluids are almost a linear function of the volume fraction and slightly higher than the results predicted by the conventional effective media theory for a well-dispersed solution. A solid-like base fluid liquid layer with a thickness of 0.6 nm was found in the simulation and this layer is believed to account for the small discrepancy between the results of MD simulation and the conventional effective media theory.     

Model of dead time when there are several recording instruments present

A model of the formation of dead time when there are several recording instruments present is proposed. Estimators of the rate of the incoming flow of events are constructed. Anzhero-Sudzhensk Division, Tomsk Pedagogical University. Tomsk University. Translated from Izvestiya Vyssikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 50–56, April, 1997.     

Diffractive vector mesons beyond the s-channel helicity conservation

We derive a full set, and determine the twist, of helicity amplitudes for diffractive production of light to heavy vector mesons in deep inelastic scattering. For large Q ² all helicity amplitudes but the double-flip are calculable in perturbative QCD and are proportional to the gluon structure function of the proton at a similar hardness scale. We find a substantial breaking of the s-channel helicity conservation, which must persist in real photoproduction also. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 9, 667–673 (10 November 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.