Dependence of Atmospheric Transparency Variations on Solar Activity

The atmospheric spectral transparency variations at 344 nm and 369 nm, averaged at eight Soviet stations between 69°N and 55°N, have been compared with sunspot numbers, or Wolf numbers (WN). The data were taken for the seasonal interval May-August during the period 1972 – 1989. Good negative correlations –0.76 and –0.82 have been found. The correlation coefficient between aerosol extinction at 344 nm and WN is equal to +0.75. Insignificant correlation is found for the transparency variations at 344 nm for stations situated to the south of latitude 50°. The best correlation with WN for both transparency and aerosol extinction at northern stations occurs for the shift of WN ahead of the optical parameters by 6 months. The connection of transparency with cosmic rays in Apatity is also examined. It displays a sign opposite to that for WN, smaller values of the correlation coefficient, and an improbable shift of transparency ahead of cosmic ray intensity. The relative changes of the transparency during a solar cycle can be evaluated at 10% in the ozone-free UVA region     

Electrostatic Potentials in Supernova Remnant Shocks

Recent advances in the understanding of the properties of supernova remnant shocks have been precipitated by theChandra and XMM X-ray Observatories, and the HESS Atmospheric Čerenkov Telescope in the TeV band. A critical problem for this field is the understanding of the relative degree of dissipative heating/energization of electrons and ions in the shock layer. This impacts the interpretation of X-ray observations, and moreover influences the efficiency of injection into the acceleration process, which in turn feeds back into the thermal shock layer energetics and dynamics. This paper outlines the first stages of our exploration of the role of charge separation potentials in non-relativistic electron-ion shocks where the inertial gyro-scales are widely disparate, using results from a Monte Carlo simulation. Charge density spatial profiles were obtained in the linear regime, sampling the inertial scales for both ions and electrons, for different magnetic field obliquities. These were readily integrated to acquire electric field profiles in the absence of self-consistent, spatial readjustments between the electrons and the ions. It was found that while diffusion plays little role in modulating the linear field structure in highly oblique and perpendicular shocks, in quasi-parallel shocks, where charge separations induced by gyrations are small, and shock-layer electric fields are predominantly generated on diffusive scales.     

Planetary,solar and astrophysical relativistic electrons: Common energization mechanisms?

Direct observations or deduced analysis indicate clearly that formation of intense fluxes of relativistic electrons is an important ingredient in the evolution of numerous active magnetized plasma systems. Examples of relativistic electron energization include the recovery phase of a planetary magnetic storm, post solar flare coronal activity and the afterglow of gamma ray bursts. It is suggested that there exists a universal mechanism, which may explain electron energization at the vastly different magnetized plasma environments. The favorite configuration consists of an inhomogeneous magnetic field anchored at a given magnetic structure and excitation of whistler waves due to external injection of low-energy non-isotropic electrons. The energization proceeds as a bootstrap process due to interaction with the propagating whistler waves along the inhomogeneous magnetic field.     

GLAST large area telescope multiwavelength planning

Gamma-ray astrophysics depends in many ways on multiwavelength studies. The Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) Collaboration has started multiwavelength planning well before the scheduled 2007 launch of the observatory. Some of the high-priority multiwavelength needs include: (1) availability of contemporaneous radio and X-ray timing of pulsars; (2) expansion of blazar catalogs, including redshift measurements; (3) improved observations of molecular clouds, especially at high galactic latitudes; (4) simultaneous broad-band blazar monitoring; (5) characterization of gamma-ray transients, including gamma ray bursts; (6) radio, optical, X-ray and TeV counterpart searches for reliable and effective sources identification and characterization. Several of these activities are needed to be in place before launch.      

Cylindrically symmetric inhomogeneous universe with electromagnetic field in string cosmology

Cylindrically symmetric inhomogeneous string cosmological model in presence of electromagnetic field is investigated. We have assumed that F ₂₃ is the only non-vanishing component of F _ij . To get the deterministic solution, it has been assumed that the expansion (θ) in the model is proportional to the eigen value σ ¹ ₁ of the shear tensor σ ⁱ _j . The physical and geometric aspects of the model are also discussed.      

A possible explanation of photon emission from supernova remnants by jitter radiation

We investigate a possibility that non-thermal X-ray emission in a supernova remnant(SNR) is produced by jitter radiation, which is the analogue of synchrotron radiation in small-scale random magnetic fields. We can fit the multi-wavelength data of SNRs RX J1713.7-3946 (G347.3-0.5) and RX J0852.0-4622 (G266.6-1.2) by constructing pure jitter and inverse Compton (IC) emission models. We find that the physical fit parameters of random magnetic fields take values of several tens of μG strength and of the order of ∼10⁷ cm correlation length. These properties of random magnetic fields in collisionless shock of SNRs are discussed.      

Numerical studies on the structure of the cosmic ray electron halo in starburst galaxies

The structure of the cosmic ray electron halo of a starburst galaxy depends strongly on the nature of galactic wind and the configuration of the magnetic field. We have investigated these dependencies by solving numerically the propagation of electrons originating in starburst galaxies, most likely in supernova remnants. The calculations are made for several models for the galactic winds and for the configuration of the magnetic fields for comparison with observations. Our simulation of a quasi-radio halo reproduces both the extended structure of ∼9 kpc and the subtle hollow structure near the polar region of the radio halo that are observed in the starburst galaxy NGC 253. These findings suggest the existence of strong galactic wind in NGC 253.      

The Galactic magnetic field as spectrograph for ultra-high energy cosmic rays

We study the influence of the regular component of the Galactic magnetic field (GMF) on the arrival directions of ultra-high energy cosmic rays (UHECRs). We find that, if the angular resolution of current experiments has to be fully exploited, deflections in the GMF cannot be neglected even for E = 10²⁰ eV protons, especially for trajectories along the Galactic plane or crossing the Galactic center region. On the other hand, the GMF could be used as a spectrograph to discriminate among different source models and/or primaries of UHECRs, if its structure would be known with sufficient precision. We compare several GMF models introduced in the literature and discuss for the example of the AGASA data set how the significance of small-scale clustering or correlations with given astrophysical sources are affected by the GMF. We point out that the non-uniform exposure to the extragalactic sky induced by the GMF should be taken into account estimating the significance of potential (auto-) correlation signals.     

Effect of nearby supernova remnants on local cosmic rays

We study in detail the effect of different particle release times from sources on the cosmic ray (CR) spectrum below 10¹⁵ eV in the Galaxy. We discuss different possible forms of particle injection such as burst-like injection, continuous injection for a finite time, injection from a stationary source and energy-dependent injection. When applied to the nearby known supernova remnants, we find that the observed CR anisotropy data favour the burst-like particle injection model for the CR diffusion coefficient   D ( E ) ∝ E ^a   with   a = 0.3 –0.6  in the local region. In this study we have also found that the contribution of the sources G114.3+0.3 and Monogem dominate if the observed anisotropy is a result of the effect of the nearby sources. Further study shows that we should not neglect the contribution of the undetected old sources to the local CR anisotropy.     

Reinvestigation of the irregularities in the 3H decay

Having in mind the potential impact of the results presented by Veprev and Muromtsev (2012) [13] on our knowledge of the universe, we reinvestigated the liquid scintillation measurement of the count rate variations of ³H. Making use of the sophisticated Quantulus liquid scintillation spectrometer, we found that the measurement of the high-energy tail of ³H spectrum may be significantly influenced by instrumental instability. Thus, the possible explanation for the relatively high count rate variations of Veprev and Muromtsev (2012) [13] can be attributed mainly to the walk of the cut-off in the integrated spectrum, although weak variations of different origin could be masked by such cut-off drifts. In our experiment we have also registered the oscillatory behavior of measured high-energy tail of ³H spectrum, but with very small amplitude (less than 0.5%), which cannot be easily explained only by instrumental instability. When the total ³H spectrum was measured, no significant variations in the count rate were found.