Alfvénic reacceleration of relativistic particles in galaxy clusters: MHD waves, leptons and hadrons     

G. Brunetti  P. Blasi  R. Cassano  S. Gabici 《Monthly notices of the Royal Astronomical Society》2004,350(4):1174-1194

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Intergalactic shock acceleration and the cosmic gamma-ray background     

Francesco Miniati 《Monthly notices of the Royal Astronomical Society》2002,337(1):199-208

We investigate numerically the contribution to the cosmic gamma-ray background from cosmic-ray ions and electrons accelerated at intergalactic shocks associated with cosmological structure formation. We show that the kinetic energy of accretion flows in the low-redshift intergalactic medium is thermalized primarily through moderately strong shocks, which allow for an efficient conversion of shock ram pressure into cosmic-ray pressure. Cosmic rays accelerated at these shocks produce a diffuse gamma-ray flux which is dominated by inverse Compton emission from electrons scattering off cosmic microwave background photons. Decay of neutral π mesons generated in p–p inelastic collisions of the ionic cosmic-ray component with the thermal gas contribute about 30 per cent of the computed emission. Based on experimental upper limits on the photon flux above 100 MeV from nearby clusters we constrain the efficiency of conversion of shock ram pressure into relativistic CR electrons to  ≲1 per cent  . Thus, we find that cosmic rays of cosmological origin can generate an overall significant fraction of order 20 per cent and no more than 30 per cent of the measured gamma-ray background.  相似文献   

INTERPLANETARY DUST AND CARBONACEOUS METEORITES: CONSTRAINTS ON POROSITY, MINERALOGY AND CHEMISTRY OF METEORS FROM RUBBLE-PILE PLANETESIMALS     

FRANS J. M. RIETMEIJER 《Earth, Moon, and Planets》2004,95(1-4):321-338

This paper discusses measured textures, porosity, chemical compositions and the minerals of interplanetary dust and meteorites from primitive planetesimals and how this information can be used to explain some of the observed physical and chemical properties of meteor phenomena.  相似文献   

The Role of Nuclei-Nuclei Interactions in the Production of Gamma-ray Lines in Solar Flares     

Boris M. Kuzhevskij  Leonty I. Miroshnichenko 《中国天文和天体物理学报》2005,5(3):295-301

Dramatic extensions of experimental possibilities (spacecraft RHESSI, CORONAS-F and others) in solar gamma-ray astronomy call for urgent, detailed theoretical consideration of a set of physical problems of solar activity and solar-terrestrial relationships that earlier may have only been outlined. Here we undertake a theoretical analysis of issues related to the production of gamma-radiation in the processes of interactions of energetic (accelerated) heavy and middle nuclei with the nuclei of the solar atmosphere (the so-called i-j interactions). We also make an estimate of the contribution of these interactions to the formation of nuclear and isotopic abundances of the solar atmosphere in the range of light and rare elements. The analysis is carried out for solar flares in the wide range of their intensities. We compare our theoretical estimates with RHESSI observations for the flare of 2002 July 23. It was shown that the 24Mg gamma-ray emission in this event was produced by the newly generated Mg nucle  相似文献   

Frozen hydrocarbon particles of cometary halos as carriers of unidentified emissions     

Irakli Simonia 《Journal of Astrophysics and Astronomy》2005,26(4):421-427

The possible nature of unidentified cometary emissions is under discussion. We propose a new model of the ice particles in cometary halos as a mixture of frozen polycyclic aromatic hydrocarbons and acyclic hydrocarbons. We describe principal properties of frozen hydrocarbon particles (FHPs) and suggest interpreting some of the unidentified cometary emission lines as the photoluminescence of FHPs. The results of comparative analysis are present.  相似文献   

Energy spectra of particles accelerated in a reconnecting current sheet with the guiding magnetic field     

Valentina V. Zharkova  Mykola Gordovskyy 《Monthly notices of the Royal Astronomical Society》2005,356(3):1107-1116

Electron and proton acceleration by a super-Dreicer electric field is investigated in the non-neutral reconnecting current sheet (RCS) with a non-zero longitudinal component of the magnetic field ('guiding field'). The guiding field is assumed parallel to the direction of electric field and constant within an RCS. The other two magnetic field components, transverse and tangential, are considered to vary with distances from the X null point of an RCS. The proton and electron energy spectra are calculated numerically from a motion equation using the test particle approach for model RCSs with constant and variable densities. In the presence of a strong or moderate guiding field, protons were found fully or partially separated from electrons at ejection from an RCS into the opposite, 'electron' and 'proton', semiplanes. In the case of a weak guiding field, both protons and electrons are ejected symmetrically in equal proportions as neutral beams. The particles ejected from an RCS with a very weak or very strong guiding field have power-law energy spectra with spectral indices of about 1.5 for protons and 2.0 for electrons. For a moderate guiding field, the energy spectra of electrons ejected into the opposite semiplanes are mixed, i.e. in the 'electron-dominated' semiplane power-law energy spectra for electrons and thermal-like for protons, while in the 'proton' semiplane they are symmetrically mirrored.  相似文献   

A new prescription for protogalactic feedback and outflows: where have all the baryons gone?     

Joseph Silk 《Monthly notices of the Royal Astronomical Society》2003,343(1):249-254

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The termination shock in a striped pulsar wind     

Y. E. Lyubarsky 《Monthly notices of the Royal Astronomical Society》2003,345(1):153-160

The origin of radio emission from plerions is considered. Recent observations suggest that radio-emitting electrons are presently accelerated rather than having been injected at early stages of the plerion evolution. The observed flat spectra without a low-frequency cut-off imply an acceleration mechanism that raises the average particle energy by orders of magnitude but leaves most of the particles at an energy of less than approximately a few hundred MeV. It is suggested that annihilation of the alternating magnetic field at the pulsar wind termination shock provides the necessary mechanism. Toroidal stripes of opposite magnetic polarity are formed in the wind emanating from an obliquely rotating pulsar magnetosphere (the striped wind). At the termination shock, the flow compresses and the magnetic field annihilates by driven reconnection. Jump conditions are obtained for the shock in a striped wind. It is shown that the post-shock magnetohydrodynamic parameters of the flow are the same as if the energy of the alternating field had already been converted into plasma energy upstream of the shock. Therefore, the available estimates of the ratio of the Poynting flux to the matter energy flux, σ, should be attributed not to the total upstream Poynting flux but only to that associated with the average magnetic field. A simple model for the particle acceleration in the shocked striped wind is presented.  相似文献   

Estimating galaxy cluster magnetic fields by the classical and hadronic minimum energy criterion     

C. Pfrommer  T. A. Enßlin 《Monthly notices of the Royal Astronomical Society》2004,352(1):76-90

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Characteristics and source of aerosols at Shiyi Glacier,Qilian Mountains, China     

XiaoYu Zhang  ZhongQin Li  Ping Zhou  ShengJie Wang 《寒旱区科学》2016,8(2):135-146

Aerosol samples were collected in the Shiyi Glacier,Qilian Mountains from July 24 to August 19,2012 and analyzed for major water-soluble ionic species(F^-,Cl^-,NO₂^-,NO₃^-,SO₄^2-,Na⁺,NH₄⁺,K⁺,Mg²⁺ and Ca²⁺) by ion chromatography. SO₄^2- and NH₄⁺ were the most abundant components of all the anions and cations,with average concentrations of 94.72 and 54.26 neq/m³,respectively,accounting for 34% and 20% of the total water-soluble ions analyzed.These mean ion concentrations were generally comparable with the background conditions in remote sites of the Qilian Mountains,but were much lower than those in certain cities in China.The particles were grouped into two dominant types according to their morphology and EDX signal:Si-rich particles and Fe-rich particles.Backward air mass trajectory analysis suggested that inland cities may contribute some anthropogenic pollution to this glacier,while the arid and semi-arid regions of central Asia were the primary sources of the mineral particles.  相似文献