On a non-primordial origin of the cosmic background radiation and pregalactic density fluctuations

Dusty pregalactic Population III objects may provide a mechanism for an effective thermalization of the star radiation. They may generate the observed microwave background and so the high cosmic photon entropy. Assuming a tepid universe a smaller primordial entropy contribution results in reasonable mass scales and amplification factors of pregalactic density fluctuations.     

超高能宇宙线电子在星际介质中的传播

本文研究能量高达1012eV以上宇宙线电子在星际介质中的传播特征, 得到了一些有趣的结果。作为一种自然的猜测, 宇宙线电子高能成份的区域性特征, 可能是导致银河系γ射线辐射的非均匀成团状分布结构的直接原因。      

Cosmic ray reacceleration on the galactic wind termination shock

Reacceleration of cosmic rays produced by galactic sources on the galactic wind termination shock is considered. The problem of the cosmic ray spectrum continuity is investigated. Numeric results are presented and discussed. We found that a smooth spectral transition from the galactic cosmic rays to the cosmic rays reaccelerated at the galactic wind termination shock is difficult to produce, if the maximum energy of accelerated particles is the same throughout the surface of the termination shock. The possible solution of this problem is the non-spherical termination shock with different maximum energies at different places of the shock.     

The KACST muon detector and its application to cosmic-ray variations studies

A single channel cosmic ray muon detector was constructed and installed in Riyadh, central Saudi Arabia, for studying the variations in the cosmic ray (CR) muon flux. The detector has been in operation since July 2002. The recorded data correspond to muons that primarily have energies between 10 and 20 GeV. The detector will be used to continuously measure the intensity of the muon components of the cosmic rays, exploring its variations and possible correlations with environment parameters. The technical aspects of this detector will be presented. Some results obtained by the detector so far will be given. These include the modulation of the CR flux on different time scales (diurnal, 27-day, and long-term variations). Additionally, the effect of a severe dust storm on the muon count rate was investigated.     

The angular distribution of the cosmic background radiation

We review the measurements of the cosmic background anisotropies at all angular scales. Special attention is devoted to experimental problems and questions concerning the data analysis.     

强磁场扰动对宇宙线调制的统计研究

对1978─1982太阳活动高年时发生的激波、强磁场扰动及激波与强磁场扰动共存这三类事件引起的宇宙线变化进行了统计研究,得到如下结果:(1)激波与强磁场扰动共存时引起的宇宙线强度下降最为显着;只有激波或强磁场扰动时,宇宙线的强度变化相对较小;(2)标志速度间断的激波是产生宇宙线Forbush下降的重要因素;(3)速度间断在强磁场扰动对宇宙线的调制中可能起一个触发的作用。      

Heliospheric implications of structure in the interstellar medium

Equilibrium models of diffuse interstellar material (ISM) near the Sun show a range of cloud densities, ionization, and temperatures which are consistent with data, although the local ISM must be inhomogeneous over ∼2 pc scales. The ISM close to the Sun has properties that are consistent with the sheetlike warm neutral (and partially ionized) gas detected in the Arecibo Millennium Survey. Local interstellar magnetic fields are poorly understood, but data showing weak polarization for nearby stars indicate dust may be trapped in fields or currents in the heliosheath nose region. Implications of this dust capture are widespread, and may impact the interpretation of the cosmic microwave background data. Observations of interstellar H⁰ inside of the solar system between 1975 and 2000 do not suggest any variation in the properties or structure of local interstellar H⁰ over distance scales of ∼750 AU to within the uncertainties.     

Solar rhythms in the characteristics of the Arctic frontal zone in the North Atlantic

Long-term changes of the Arctic frontal zone characteristics near the south-eastern coasts of Greenland were considered, the NCEP/NCAR reanalysis data being used. It was found that in the cold half of the year the temperature gradients in the layer 1000–500 hPa in the region under study reveal strong ∼10-yr and ∼22-yr periodicities that seem to be related to solar activity cycles. The results obtained suggest the influence of solar activity and cosmic ray variations on the structure of the temperature field of the troposphere resulting in the changes of the temperature contrasts in the Arctic frontal zone that, in turn, may affect the intensity of cyclogenesis at middle latitudes. The detected effects seem to indicate an important part of frontal zones in the mechanism of solar activity and cosmic ray variation influence on the development of extratropical baric systems. It is suggested that the variations of the temperature gradients revealed in the Arctic frontal zone are due to the radiative forcing of cloudiness changes which may be associated with geomagnetic activity and cosmic ray variations.     

宇宙线福布什下降的数值模拟

本文从银河宇宙线的太阳调制方程出发,认为激波对宇宙线的影响是由一扰动区产生的。在此扰动区中太阳风速度增加,扩散系数下降。由此进行了数值模拟,模拟结果表明:扩散系数的下降在产生福布什下降时要比太阳风速度的增加更为有效;福布什下降在近日球层内向外传播时,其幅度随径向距离的增大而衰减;两个无相互作用的激波同时存在时所产生的福布什下降为每个激波单独存在时的福布什下降的简单线性迭加。      

On transmissivity of low energy cosmic rays in disturbed magnetosphere

Access of low energy cosmic rays to any position on the Earth depends on the state of the magnetosphere. Anisotropy of cosmic rays, deduced from the neutron monitor network, must assume the variable transmissivity of the magnetosphere especially during the geomagnetic disturbances. We illustrate that computations based on different available models of geomagnetic field during selected strong geomagnetic disturbances in 2003 and 2004 imply different profiles of cut-off rigidities in time, different transmissivity functions and different asymptotic directions. Using of cosmic ray records by neutron monitors at middle and low latitudes during geomagnetically active periods, in addition to cosmic ray anisotropy in interplanetary space deduced from high and low energy cosmic ray ground based measurements, may be used for checking validity of geomagnetic field models.     

Observational constraints on dark matter in the universe

Application of the cosmic virial theorem to galaxy redshift surveys suggests an open universe - if the dark material is distributed in the same way as galaxies. Here we investigate four redshift surveys. We present new results on the amplitudes of the two- and three-point galaxy correlation functions and we estimate the relative peculiar velocities in the deep redshift survey of Kirshner and co-workers (1983). Next, we review evidence which suggests that dark material is clustered on scales comparable to the optical radii of galaxies. In particular, we use spectroscopic and photometric observations to set constraints on the mass distribution in elliptical galaxies.     

The relationship between plasma effects and cosmic radiation studied with TriTel-LMP measurements during the ESEO mission

The main point of the paper is to use the simultaneous measurements of the energetic particle flux by TriTel and those of electron density by a Langmuir probe to study the question of to what extent solar electromagnetic and corpuscular radiation (galactic cosmic rays, particle precipitation from the radiation belts) are responsible for the ionization of the atmosphere. The electron density measured by the Langmuir probe is the sum of the ionization produced by the solar electromagnetic radiation and that due to the corpuscular radiation. The ionization produced by the solar electromagnetic radiation may be computed. The flux of energetic particles in an energy range may be determined by taking the difference between the threshold energy of the TriTel telescopes and the energy corresponding to the local cut-off rigidity. As the ESEO satellite will have a quasi-polar and circular orbit, the cut-off rigidity will change from low to high latitudes, thus enabling the assignment of different energy bands for the telescopes. Thus, it will be possible to determine which energy bands of particle produce ionization at different latitudes.     

Constraints on injection parameters of cosmic rays in the Galactic center from resolved HESS observations

In this study, we investigate how restrictive the γ-ray emission from the Galactic center region, as seen by HESS and other Cherenkov air shower arrays, is against various models for cosmic ray injection. We derive diffusion coefficients which fit the observed spatial scales of diffuse γ-ray emission from the extended emission associated with the molecular clouds SgrA, B and C. Using these diffusion coefficients, we then obtain a limit for time scale of assumed recent proton acceleration near the SMBH, as the spatial size of SgrA^∗ in VHE γ-rays has to be consistent with the observed unresolved HESS point source size at this position. The signal from this hadronic component may be mixed with the expected VHE inverse Compton emission from the nearby unresolved pulsar wind nebula.     

Cosmic ray variations of solar origin in relation to human physiological state during the December 2006 solar extreme events

There is an increasing amount of evidence linking biological effects to solar and geomagnetic disturbances. A series of studies is published referring to the changes in human physiological responses at different levels of geomagnetic activity. In this study, the possible relation between the daily variations of cosmic ray intensity, measured by the Neutron Monitor at the Cosmic Ray Station of the University of Athens (http://cosray.phys.uoa.gr) and the average daily and hourly heart rate variations of persons, with no symptoms or hospital admission, monitored by Holter electrocardiogram, is considered. This work refers to a group of persons admitted to the cardiological clinic of the KAT Hospital in Athens during the time period from 4th to 24th December 2006 that is characterized by extreme solar and geomagnetic activity. A series of Forbush decreases started on 6th December and lasted until the end of the month and a great solar proton event causing a Ground Level Enhancement (GLE) of the cosmic ray intensity on 13th December occurred. A sudden decrease of the cosmic ray intensity on 15th December, when a geomagnetic storm was registered, was also recorded in Athens Neutron Monitor station (cut-off rigidity 8.53 GV) with amplitude of 4%. It is noticed that during geomagnetically quiet days the heart rate and the cosmic ray intensity variations are positively correlated. When intense cosmic ray variations, like Forbush decreases and relativistic proton events produced by strong solar phenomena occur, cosmic ray intensity and heart rate get minimum values and their variations, also, coincide. During these events the correlation coefficient of these two parameters changes and follows the behavior of the cosmic ray intensity variations. This is only a small part of an extended investigation, which has begun using data from the year 2002 and is still in progress.     

The high-LET radiation component measured during the EUROMIR-94 mission.

Stacks of CR-39 plastic nuclear track detectors were mounted inside the MIR-station during the EUROMIR-94-mission. We present LET-spectra determined separately for long range cosmic ray heavy ions and for short range target fragments produced in nuclear interactions of cosmic rays and measured charge distributions for relativistic and stopping particles.     

Recent results form measurements of the energy spectrum of cosmic-ray induced neutrons aboard an ER-2 airplane and on the ground.

Crews of future high-altitude commercial aircraft may be significantly exposed to atmospheric cosmic radiation from galactic cosmic rays (GCR). To help determine such exposures, the Atmospheric Ionizing Radiation Project, an international collaboration of 15 laboratories, made simultaneous radiation measurements with 14 instruments on a NASA ER-2 high-altitude aircraft. The primary instrument was a sensitive extended-energy multisphere neutron spectrometer, which was also used to make measurements on the ground. Its detector responses were calculated for neutrons and charged hadrons at energies up to 100 GeV using the radiation transport code MCNPX. We have now recalculated the detector responses including the effects of the airplane structure. We are also using new FLUKA calculations of GCR-induced hadron spectra in the atmosphere to correct for spectrometer counts produced by charged hadrons. Neutron spectra are unfolded from the corrected measured count rates using the MAXED code. Results for the measured cosmic-ray neutron spectrum (thermal to >10 GeV), total neutron fluence rate, and neutron dose equivalent and effective dose rates, and their dependence on altitude and geomagnetic cutoff generally agree well with results from recent calculations of GCR-induced neutron spectra.     

On ultra-high energy cosmic rays: Origin in AGN jets and transport in expanding universe

The cosmic ray source spectrum produced by AGN (active galactic nucleus) jets is calculated. A distinctive feature of these calculations is the account for the jet distribution on kinetic energy. The expected cosmic ray spectrum at the Earth is determined with the use of a simple numerical code which takes into account interactions of ultra-high energy protons and nuclei with the background radiation in an expanding universe.     

North–South asymmetry in cosmic ray fluxes as measured in the stratosphere and in selected solar wind parameters in the near-Earth space

North–South asymmetry in the cosmic ray fluxes as resulted from the long-term balloon measurements in the northern and southern polar stratosphere does not agree with that found from the neutron monitor data. In order to reveal possible sources of the observed asymmetry, selected interplanetary parameters were examined. North–South asymmetry relative to the heliospheric neutral sheet was considered for solar wind velocity, plasma density and some other solar plasma parameters. It is shown that North–South asymmetry of the solar wind velocity and plasma density depends on the Earth’s heliolatitude and the phase of the 11-year solar activity cycle. This may be relevant to the results of cosmic ray measurements in the stratosphere.     

Propagation of cosmic ray nuclei above 50 GeV/amu

It is now well-known that the relative abundance of secondary cosmic ray nuclei which are produced by spallation in interstellar space depends on energies. The mechanism responsible for this energy dependence are not well understood because of the scarcity of data on the cosmic ray composition at energy above 50 GeV/amu. The University of Chicago experiment on the Spacelab-2 flown by the Space Shuttle in 1985 is aimed at the measurement of the elemental composition in this unexplored energy regime. Our latest results on the energy dependence of the secondary to primary abundance ratio using the pairs of elements B,C and N,O, are discussed.