Forbush decrease in the intensity of cosmic rays in a toroidal model of a magnetic cloud

The time dynamics of the particle distribution function in a magnetic cloud with the shape of a toroidal segment with the characteristic (forceless) structure of a magnetic field has been calculated. The shape of the cloud at the subsequent propagation in the interplanetary space has been determined by the kinematic model. The magnetic field of the cloud is calculated using the freezing-in condition. A significant effect of regions connecting the magnetic cloud with the Sun on the propagation of particles in the region of perturbation has been revealed. The calculation of the particle density and anisotropy of the intensity demonstrates reasonable agreement with the measurements. The results indicate the decisive role of the characteristic structure of the magnetic field in the time dynamics of the Forbush decrease in the intensity of cosmic rays.     

Low cloud properties influenced by cosmic rays

The influence of solar variability on climate is currently uncertain. Recent observations have indicated a possible mechanism via the influence of solar modulated cosmic rays on global cloud cover. Surprisingly the influence of solar variability is strongest in low clouds (相似文献   

Scattering of galactic cosmic rays by a magnetic cloud injected into interplanetary space during active solar processes

The scattering of charged particles as they pass through areas of the interplanetary magnetic field with large-scale inhomogeneities (magnetic clouds) is studied using the Monte Carlo method and the numerical simulation of trajectories. Charged particles (protons) with energies ranging from 1 to 100 GeV in magnetic clouds with sizes of 0.01–0.1 a.u. and magnetic flux densities of 5 to 50 nT are modeled. It is established that an important factor in determining the nature of galactic cosmic ray scattering is the relationship between the Larmor radii of particles, the size of a magnetic cloud, and the degree of magnetic field inhomogeneity.     

Solar cosmic rays

Summary This report is a brief overview of the energetic-particle phenomena related to solar activity discussed at the XXIV International Cosmic-Ray Conference. In the rapporteur's opinion, the most significant results to be highlighted are: 1) the new higher-energy measurements of the solar energetic ion charge state which seem to be consistent with the older measurements at ∼1 MeV/nucleon, and 2) the many reports of extended gamma-ray production during solar flares with multiple episodes of emission implying multiple episodes of particle acceleration. Rapporteur talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

Variational estimates of the diffusion coefficient of cosmic rays in a random magnetic field

A variational method is used to obtain estimates of the effective particle transport coefficients in a random static magnetic field. The particle propagation is described by an anisotropic diffusion equation. The diffusion coefficient parallel to the local magnetic field is much greater than the transverse diffusion coefficient. For large-scale magnetic-field variations the diffusion is described by effective coefficients. The variational approach can be used to find the effective parallel and perpendicular diffusion coefficients. It was shown that the instability growth rate of the magnetic field lines determines the upper estimate of the effective transverse diffusion coefficient. Zh. éksp. Teor. Fiz. 114, 398–405 (August 1998)     

Origin of cosmic rays

Cosmic rays were discovered in 1911 but it is only now that some ideas are beginning to emerge as to their origin. This paper will examine the present evidence concerning the origin question over the whole energy range, from 10⁹ eV to 10²⁰ eV. At the lowest energies, (10⁹–10¹⁰ eV), the new subject of gamma ray astronomy plays a crucial role and a galactic origin is favoured. At higher energies (10¹²–10¹⁷ eV) recent measurements of the anisotropies in arrival directions also suggest a galactic origin, although the evidence is not as strong. At the very highest energies it seems likely that some, at least, of the particles come from outside the galaxy although the non-existence of the cut-off at about 6 × 10¹⁹ eV arising from interactions with the cosmological relict radiation provides a paradox. The likely future areas of advance in this fascinating subject will be indicated. Based on the B. B. Roy memorial lectures delivered at Calcutta University, February 1–3, 1978.     

Search for antihelium in cosmic rays

The Alpha Magnetic Spectrometer (AMS) was flown on the space shuttle Discovery during flight STS-91 in a 51.7° orbit at altitudes between 320 and 390 km. A total of 2.86×10⁶ helium nuclei were observed in the rigidity range 1 to 140 GV. No antihelium nuclei were detected at any rigidity. An upper limit on the flux ratio of antihelium to helium of <1.1×10⁻⁶ is obtained.     

Propagation of solar cosmic rays in loop-like interplanetary magnetic field structures

Features of propagation of relativistic solar cosmic rays in magnetic clouds have been considered on the basis of model calculations. Magnetic clouds have a structure of magnetic flux ropes and are extended from the Sun to the Earth via coronal mass ejections. Features of propagation of particles of different energies in a magnetic cloud are discussed. The propagation of high-energy solar protons in the loop-like structure of the interplanetary magnetic field in the event of October 28, 2003 is analyzed.     

Search for anisotropy of ultrahigh-energy cosmic rays

It is shown that a statistically significant anisotropy exists in the arrival directions of cosmic rays with energies ∼1×10¹⁷ eV and 4×10¹⁸ eV. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 5, 289–292 (10 September 1997)     

Paleoastrophysics and cosmic rays

Summary A discussion is given of the status and potential of studying the cosmic-ray flux level over long time scales by high-precision measurement of cosmogenic isotopes content in natural archives of cosmic radiation. Invited talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

A theory of cosmic rays

We present a theory of non-solar cosmic rays (CRs) in which the bulk of their observed flux is due to a single type of CR source at all energies. The total luminosity of the Galaxy, the broken power-law spectra with their observed slopes, the position of the ‘knee(s)’ and ‘ankle’, and the CR composition and its variation with energy are all predicted in terms of very simple and completely ‘standard’ physics. The source of CRs is extremely ‘economical’: it has only one parameter to be fitted to the ensemble of all of the mentioned data. All other inputs are ‘priors’, that is, theoretical or observational items of information independent of the properties of the source of CRs, and chosen to lie in their pre-established ranges. The theory is part of a ‘unified view of high-energy astrophysics’ — based on the ‘Cannonball’ model of the relativistic ejecta of accreting black holes and neutron stars. The model has been extremely successful in predicting all the novel properties of Gamma Ray Bursts recently observed with the help of the Swift satellite. If correct, this model is only lacking a satisfactory theoretical understanding of the ‘cannon’ that emits the cannonballs in catastrophic processes of accretion.     

Spectrum of ultrahigh-energy cosmic rays

Detailed calculation of the energy spectra of ultrahigh-energy cosmic rays has been performed. The spectral features related to the interaction of protons with cosmic microwave background have been analyzed. The calculated spectra are compared with the experimental data obtained at the giant detectors for ultrahigh-energy cosmic rays.     

Search for heavy particles in cosmic rays

A search for heavy, long-lived particles has been made in the cosmic rays. The observations may possibly be explained in terms of known particles, but they appear to be more easily explained in terms of a flux $\text{? 6.10}{}^{\mathrm{?9}}\text{cm}{}^{\mathrm{?2}}\text{sec}{}^{\mathrm{?1}}\text{sr}{}^{\mathrm{?1}}$ if singly charged particles having mass $\text{? 6 m}{}_{\mathrm{<mtext>p</mtext>}}$.     

Plasma wakefield acceleration for ultrahigh-energy cosmic rays

A cosmic acceleration mechanism is introduced which is based on the wakefields excited by the Alfvén shocks in a relativistically flowing plasma. We show that there exists a threshold condition for transparency below which the accelerating particle is collision-free and suffers little energy loss in the plasma medium. The stochastic encounters of the random accelerating-decelerating phases results in a power-law energy spectrum: f(epsilon) proportional, variant 1/epsilon(2). As an example, we discuss the possible production in the atmosphere of gamma ray bursts of ultrahigh-energy cosmic rays (UHECR) exceeding the Greisen-Zatsepin-Kuzmin cutoff. The estimated event rate in our model agrees with that from UHECR observations.     

The search for antimatter in cosmic rays

The search for antimatter in the universe is a page in the history of the Ioffe Physicotechnical Institute (IPTI). Experiments on spacecraft and high-altitude balloons, begun in the 1960s, yielded information on to the presence or absence of antimatter stars or galaxies according to evidence arising in explosive processes in these objects. Antiprotons with energies of 2–5 GeV in galactic cosmic rays were observed at the end of the 1970s in balloon experiments by the Cosmic Spectrometry Laboratory at the IPTI. These studies were done using a magnetic spectrometer at altitudes with a residual pressure of 10 g/cm² with a threshold geomagnetic rigidity of 3 GV. High-latitude experiments in the 1980s, yielding the first measurements of the flux of galactic antiprotons with energies of 0.2–2 GeV, gave some indication of the mechanism by which they are generated. The measured ratios of the fluxes of antiprotons and protons in the cosmic rays are 2.4 _−1.3 ^+2.4 ×10⁻⁴ and 6 ₋₅ ⁺¹⁴ ×10⁻⁵ at energies of 2–5 and 0.2–2 GeV, respectively. Subsequent balloon-borne experiments employing magnetic spectrometers by groups from the USA and Japan have confirmed the results obtained by the IPTI. Experimental and theoretical work on the search for antiparticles in cosmic rays is summarized and the astrophysical consequences of this research are discussed. Experimental data on the detection of antiparticles in galactic cosmic rays indicate that there are no objects made of antimatter within the local group of galaxies. Zh. Tekh. Fiz. 69, 99–103 (September 1999)     

Search for extragalactic sources of ultrahigh-energy cosmic rays

Possible extragalactic sources of cosmic rays with energies above 4 × 10¹⁹ eV detected at the Yakutsk EAS array are sought. The correlation of the shower arrival directions with objects from Véron’s catalog that are located closer than 100 Mpc from the Earth confirms the observations at the Pierre Auger Observatory, as well as the Greisen-Zatsepin-Kuzmin effect on the spectrum of cosmic rays. The detailed analysis of the data reveals the classes of objects belonging to the active galactic nuclei that are the most probable sources of ultrahigh-energy cosmic rays.     

Prompt-muon production in cosmic rays

Summary We discuss here the results obtained calculating the contribution of prompt muons in the vertical atmospheric muon flux, computed taking into account the up-to-date data from experiments at accelerators and the most recent theoretical achievements on charm generation in nucleon-air nucleus interactions. Our results are compared with the experimental data obtained with underground detectors.

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Riassunto Si discutono in questo lavoro i risultati ottenuti sul contributo di muoni pronti al flusso atmosferico verticale dei muoni, calcolato utilizzando i dati piú recenti di esperimenti degli acceleratori ed i risultati teorici sulla produzione di particelle charmate in interazioni nucleoni-nuclei atmosferici. I risultati ottenuti sono confrontati con i dati sperimentali forniti da esperimenti sotterranei.

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Резюме Мы обсуждаем результаты вычислений вклада мгновенных мюонов в вертикальный роток атмосферных мюонов. Вычисления учитывают данные из зкспериментов на ускорителях и недавние теоретические предсказания по рождению очарованных частиц при, взаимодействиях нуклонов с ядрами воздуха. Наши результаты сравниваются с зкспериментальными данными, полученными с помощью подземных детекторов.