On the intensity of galactic cosmic rays in the inner heliosphere during epochs of minimum solar activity

The behavior of the intensity of cosmic rays of galactic origin in the inner heliosphere (r ?? 10 a. u.) during the minima of solar cycles 20?C24 is considered. The features of cosmic ray characteristics in the last anomalously long and deep minimum of solar cycle 24 (2007?C2010) are discussed.     

On the structure of galactic cosmic ray intensity during its long-term variations

The structure of GCR intensity and its changes during the solar magnetic cycle are analyzed by numerically solving its transport equation. We propose a research method that allows us to use the intermediate results from numerical calculations, to resolve the intensity of galactic cosmic rays into components caused by sunspot and magnetic solar cycles, and to monitor the changes in energy in different parts of the heliosphere and different phases of the cycle. A method for dividing intensity into its components associated with the main physical processes determining the modulation of galactic cosmic rays is also proposed.     

Paleoastrophysics: Progress and prospects

Results of highly accurate measurements of the radiocarbon concentration in the annual growth rings of trees over the last 400 years are presented. The temporal behavior of the intensity of galactic cosmic rays is reconstructed for the first time for the periods before, during, and after a deep and extended solar activity minimum — the Maunder minimum (1645–1715). It was established that even during the epoch of a deep solar minimum, the intensity of the galactic cosmic rays experienced solar modulation. The time profile of the generation of high-energy gamma radiation from the supernova explosion of 1006 is established. It is shown that processes of particle acceleration and generation of high-energy gamma rays take place with a three-year delay relative to the onset of the optical flare. The time profile of the generation of solar cosmic rays was obtained for the first time over the last thirty cycles of solar activity by precision measurements of the nitrate content in the polar ice cap. It is shown that solar flares accompanied by the generation of cosmic rays occur during the growth and decay phase of solar activity (measured by the Wolf numbers). Research prospects in the field of experimental paleoastrophysics are discussed. Zh. Tekh. Fiz. 69, 90–93 (September 1999)     

Shock-wave and plasma-pinch mechanisms of galactic cosmic-ray production

Based on recent discoveries, we show that it is appropriate to complement the standard shock-wave model for the production of galactic cosmic rays by a plasma-pinch model. The latter describes well the production of high-energy cosmic rays, yields a simple formula for their intensity, and allows the threshold pattern of the knee-type kink in the secondary particle spectrum and a number of unusual phenomena observed above the threshold to be explained.     

Two-decade experience of application of plastic nuclear track detectors to cosmic ray research on satellites and orbital space stations

The work generalizes the results obtained during the last two decades in our spaceborne experiments aimed at studying galactic cosmic rays and cosmic ray anomalous component and carried out using solid-state nuclear track detectors (SSNTD) mounted mostly outside spacecraft. The experimental equipment and the techniques for identifying cosmic ray ions and for calculating particle flux values are described. The experimental data are used to construct a modified model for the fluxes and spectra of cosmic ray protons and heavy nuclei to be calculated to within a higher accuracy compared with the earlier models.     

Connections between neutron monitor count rate and solar modulation strength

We suggest a new approach to the normalisation of neutron monitor response to galactic cosmic rays. The reference normalisation count rate is the neutron monitor response to the model unmodulated flux of galactic cosmic rays. A comparison of the actually recorded neutron monitor count rate with the calculated normalisation count rate can provide one with an observationally obtained true-of-date integral measure of the current level of solar modulation of galactic cosmic rays. The Slovak VEGA grant agency is acknowledged for the grant 2-5137.     

Arrival directions and chemical composition of ultrahigh-energy cosmic rays

Chemical composition of ultrahigh-energy cosmic rays is estimated through the reliably determined (both experimentally and theoretically) distribution of the number of showers in the galactic latitude. Experimental data at energies of ～10¹⁹ eV agree with the theoretical calculations, provided that cosmic rays involve predominantly heavy nuclei. An enhanced flux of cosmic rays from the galactic plane is detected at energies of ～10¹⁹ eV.     

Cosmic ray intensity dynamics in the region ahead of the interplanetary shock front

The galactic cosmic rays intensity dynamics prior to the onset of the geomagnetic storm of September 9, 1992, are calculated using a new kinetic method. A comparison of the calculation results and the observational data from ground-level detectors shows satisfactory agreement on both amplitude and time.     

Primary cosmic ray composition at energies from 10<Superscript>17</Superscript> to 10<Superscript>18</Superscript> eV according to the EAS MSU array data

EAS MSU array data on the composition of primary cosmic rays at energies above 10₁₇ eV are analyzed. The problem of existence of a cosmic ray component that is not related to the conventional mechanism of formation of galactic cosmic rays is considered and the fraction of γ rays in primary cosmic rays is estimated.     

Very Local Interstellar Spectra for Galactic Electrons,Protons and Helium

The local interstellar spectra (LIS) for cosmic rays at energies below ～30 GeV/nuc are increasingly obscured from view at Earth by solar modulation, the lower the energy becomes. These charged particles encounter significant changes in the heliosphere, over an 11-year cycle, which include processes such as convection, diffusion, adiabatic energy losses and gradient, curvature and current sheet drifts. Particle drifts cause charge-sign-dependent modulation and a 22-year cycle, adding complexity to determining the respective very LIS from observations only at Earth. However, with measurements now made by the Voyager 1 spacecraft in the vicinity of the heliopause, it is possible to determine a very LIS for galactic electrons between ～5 and ～120 MeV. At these low energies, also galactic protons observed in the outer heliosphere had been completely obscured by the so-called anomalous component which is accelerated inside the heliosheath. Since August 2012, these anomalous cosmic rays are substantially depleted at Voyager 1 so that for cosmic ray ions, it is now possible to obtain a lower limit to their very LIS. Combining numerical modelling of solar modulation with the accurate measurements by the PAMELA mission and with Voyager observations, the lower limit of the very LIS for electrons, protons and helium and other ions can be determined from ～5 MeV and above. These spectra are called heliopause spectra which is considered to be the lowest possible very LIS. Also, from an astrophysics point of view, the determination of what can be called a very LIS, not just an averaged galactic spectrum, is encouraging. The mentioned aspects are discussed, focusing on a comparison of recent heliospheric observations and corresponding solar modulation modelling.     

The surfatron acceleration of cosmic rays in the galactic plasma

The optimum conditions for a prolonged holding of charged particles resonantly trapped from the galactic plasma by nonlinear waves and for the acceleration of these particles to high energies by the surfatron mechanism are established. The density of particles trapped by the plasma waves of large amplitude and by the quasitransverse magnetosonic shock waves is estimated. Various reasons leading to possible breakage of the process of surfatron acceleration of cosmic rays in the Galaxy are considered. Within the framework of the surfatron acceleration mechanism, galactic cosmic rays originate predominantly from the interstellar plasma and their energy spectrum is formed in two stages. In the first stage, some of the galactic plasma particles are accelerated from thermal energies to 10¹⁵ eV/nucleon; in the second stage, the cosmic rays may continue gaining energy up to 10¹⁹ eV/nucleon and above.     

Cosmic rays and variations of the concentration of active nuclei of condensation and crystallization in the Earth’s atmosphere

A possible mechanism of the influence of cosmic rays on the concentration of neutral active nuclei of condensation and crystallization in the Earth’s atmosphere is considered. The mechanism is based on the variation in the transparency of the atmosphere under cosmic rays. It is shown that the concentration of active nuclei of condensation increase at low and middle altitudes, while the concentration of stable ice nuclei decreases. This effect and the change in the growth rate of drops can lead to correlation between the galactic cosmic rays and cloud cover anomalies at low altitudes and to the absence of correlation at middle altitudes. It is shown that the correlation between galactic cosmic rays and cloud cover anomalies can be absent at high altitudes.     

On the possible contribution of solar-cosmic factors to the global warming of XX century

The effect of changes in the total solar irradiance and intensity of galactic cosmic rays on the increase in the global temperature of the Earth over the last 120 years was investigated using a one-dimensional energy-balance climate model. It is shown that the joint effect of solar and cosmic factors during this periodcan lead to an increase in the average temperature of the northern hemisphere by 0.25–0.35°C. It is concluded that the solar luminosity and the cosmic-ray flux can make a significant contribution to the global warming of the last century.     

Search for periodicities in galactic cosmic rays,sunspots and coronal index before arrival of relativistic protons from the sun

Using different approaches and techniques of wavelet analysis we analyze variations (oscillations) of galactic cosmic rays, solar spot number, and coronal index of solar activity before ground level enhancements of solar cosmic rays. Obtained results are discussed in frames of recent ideas about periodicity phenomena in the photosphere, and corona of the Sun, interplanetary medium, and cosmic rays.     

Observations of energetic particles with EPAC on Ulysses in polar latitudes of the heliosphere

Summary Measurements with the EPAC energetic-charged-particle instrument aboard Ulysses show between −15° and −65° ions and, to some extent, also electrons apparently accelerated by shocks associated with a cororating interaction region (CIR) operating at low latitudes. Particles could have reached Ulysses along magnetic-field lines which connect to the shocks in the more distant heliosphere. Such connections evidently do not exist above −65°. Between the recurrent streams we find the underlying composition to be similar to that of the anomalous component of cosmic rays (ACR). One channel (ELH), sensitive also to high-energy protons (E>210 MeV), shows that, superimposed to the large-scale heliospheric modulation of galactic ions, a 26-day variation of the flux is observed. Such modulation is also observed for the ACR, in phase with the galactic particle modulation, but anticorrelated to the CIR-related low-energy particles. An estimate of the latitudinal and radial gradients of the galactic cosmic rays at 1 GV gives +0.4%/degree and −11%/AU, respectively. Paper presented at the Special Session on the Ulysses mission of the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

Two-dimensional transport equation for GCR in three-dimensional models of the heliosphere

An axisymmetric transport equation for galactic cosmic rays is proposed, which is a consequence of an equation three-dimensional in spatial coordinates. In this equation, the three-dimensionality is caused by the heliospheric current sheet of arbitrary shape. The feature of the proposed equation consists in the consideration of the source associated with variations of the three-dimensional GCR intensity. The equation can be used to describe GCR modulation processes in the GCR heliosphere.     

A Statistic Model for Galactic Cosmic Rays

Supposed that all of cosmic ray particles of energy below 3×10¹⁸eV are mainly originated and accelerated in an individual explosion of the galactic supernovae(SNs).By using an isotropic diffusion propagation model,non-steady state density of the iron nucleus is investigated.Considering the effect of extra-galactic cosmic rays and the variety of the galactic cosmic ray nuclei,the statistic model of galactic cosmic rays with a reasonable distribution of the SNs in space and time can account for the spectrum of cosmic ray in the energy range of 10¹²—10²⁰eV quitewell.     

Cosmic rays in the Earth’s atmosphere

This paper presents a brief historical overview of studies of cosmic rays in the Earth’s atmosphere, which were initiated and led by S.N. Vernov for over 50 years. The main results of these studies that were obtained in recent decades are given. They include the study of the processes of generation and propagation of solar cosmic rays, the modulation of galactic cosmic rays in the heliomagnetosphere, and the role of cosmic rays in atmospheric processes.     

New dosimeters for solar-flare radiations

From the extensive investigations carried out since 1992 with the dosimetric ANPA-stack on 107 long-haul flights, it is possible to conclude that the cumulative dose per flight on a given route changes within less than 20% among different repeated routes, two different aircrafts (Boeings 747 and 767), and among different locations within the aircraft. In contrast to galactic cosmic rays, solar-flare radiation is totally unpredictable and extremely variable in terms of energy spectrum, intensity, direction, duration and starting time.

Most of the dosimetric systems used to date for the galactic cosmic rays may not be appropriate for solar-flare-radiation dosimetry. For this reason, different dosimetric systems have been investigated for both the retrospective and prospective dosimetry of solar flares. While waiting for the rare solar flare to occur, these dosimetric systems could be used for the validation of the computer-estimated route doses and/or for dosimetry in space, where frequent measurements of solar-flare events are needed.