Behavior of the intensity of galactic and anomalous cosmic rays in the outer heliosphere and large-scale electric fields

The behavior of the intensity of anomalous and galactic cosmic rays in the outer heliosphere is compared. The previous hypothesis, according to which the lowest energy galactic cosmic rays affected by large-scale electric fields far beyond the termination shock wave of the solar wind may contribute to the behavior of the anomalous component intensity, is analyzed.     

Temporal changes in the energy spectrum of Forbush decreases in 20–23 solar activity cycles

Variations in the energy spectrum of galactic cosmic rays during Forbush decreases registered in the 20–23 solar activity cycles are studied, using the data from neutron monitors and the Yakutsk cosmic ray spectrograph. It is shown that the Forbush decreases in the 23rd cycle of solar activity had a harder energy spectrum than in the three previous cycles, due to the relatively low level of turbulence of the interplanetary magnetic field during the 23rd solar activity cycle.     

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.     

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.     

On the formation of spot and magnetic cycles in the galactic cosmic ray intensity in the minima of solar activity

The problems of the determination and separation of variations in the galactic cosmic ray intensity, caused by the spot-forming activity and polarity of high-latitude solar magnetic fields, are discussed. Based on the solution of the boundary-value problem, some features in the intensity formation at solar cycle minima are formulated.     

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)     

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.     

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.     

Approximately 2400-Year Cycle in the Concentration of Cosmogenic Radionuclides: Sources of Variations

Cosmogenic isotopes, including ¹⁴C, ¹⁰Be, and ⁷Be, are produced in the Earth’s atmosphere under the effect of cosmic rays. The rate of their production is determined by several factors, such as the intensity of primary galactic cosmic rays, the level of solar activity, and the strength of the Earth’s magnetic field. Changes in the isotope concentrations and distributions receive contributions from mixing processes proceeding in the surrounding medium: the atmosphere, biosphere, and oceans. The isotopes ¹⁴C and ¹⁰Be are the most important for studying solar activity and climate. Investigation of isotope concentrations reveal that there are both long-term trends and cyclic components. As for ¹⁴C, the long-term component caused by the change in the magnetic dipole moment of the Earth with a characteristic time of about 10⁴ years is the most commonly known. It is well known that the concentrations of cosmogenic isotopes change cyclically with time. The ~2400-year cycle (Hallstatt cycle) and the ~210-year cycle (de Vries cycle) are the most famous. In the present article, we discuss the possible origin of the ~2400-year cycle.     

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.     

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 theory of particle diffusion in a strong random magnetic field with an allowance for higher multipole moments of the distribution function

The kinetic equation including a small-scale collisional integral for the particles propagating in a strong random and regular magnetic field [29] is solved by expanding the distribution function into series in spherical harmonics of the particle momentum angles. Using methods of the quantum theory of the angular moment [41], the equations for higher multipole moments of the distribution function in the space of momentum angles are derived and solved in the stationary case for the galactic cosmic rays in interplanetary space. The observed amplitudes and phases of the diurnal variation harmonics can be explained using the results of measurements of the interplanetary magnetic field performed on board the Ulysses spacecraft [12–14] and other satellites [45, 46] with an allowance for redistribution of the interplanetary and interstellar magnetic field lines. The spatial structure of the convection and diffusion fluxes of the galactic cosmic rays is refined. Formulas taking into account a change in the Earth’s axis tilt relative to the direction toward the Sun are derived, which allow the annual changes in contributions to the diurnal variation harmonics to be determined. The equation of diffusion taking into account the 2nd harmonic is obtained, and the contribution of this effect to the relative particle density in the cosmic rays in a spherically symmetric case is analyzed.     

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.     

Rigidity spectrum and cosmic ray anisotropy during sporadic events in July 2000

A spectrographic global survey is performed to study the rigidity spectrum and anisotropy of galactic cosmic rays using spacecraft data and data obtained via ground-based observations of cosmic rays (CRs) by a worldwide network of stations during the GLE of July 14, 2000, and the strong magnetic storm related to the coronal mass ejection (CME) accompanying the solar flare. The CR rigidity spectrum observed over the range of 1 to ～20 GV during this period is shown to be described not only by the power function of particle rigidity; the distribution of CRs in the earthward direction varies over time and depends on their energy.     

VH-nuclei cosmic ray tracks in silicate minerals of howardites: A regolith stage of parent body formation

Natural tracks in pyroxene and plagioclase crystals from Erevan and Kapoeta howardites are due to irradiation by both galactic and solar cosmic rays.     

Forbush decreases in the 19th solar cycle

The 19th solar cycle was characterized by abnormally high solar activity; unfortunately, the possibilities of observing it were limited. Ground-based observations of cosmic rays and geomagnetic activity are among the few types of continuous measurements that allow statements about the events of 19th cycle and their comparison with events of other cycles. Comparison of the events in cosmic rays with solar and geomagnetic activities shows that the number and strength of magnetic storms in the 19th cycle correspond to an abnormally high number of sunspots. However, large Forbush decreases were lacking in this cycle. The most powerful ICMEs of the 19th cycle were generally weaker than the greatest ones in later periods.     

On the cosmogenic radionuclides in meteorites

Summary Different fluxes and spectra of galactic cosmic rays (GCR) and solar cosmic rays result in a wide variety of radioactive and stable-nuclides production rates. The records of cosmic-ray interactions, have been studied in terrestrial archives, in meteorites, cosmic dust and lunar samples. We present here some results obtained in our laboratory on the study of cosmogenic radionuclides produced in meteorites which fell in the last century. The laboratory is situated in the underground station of Monte dei Cappuccini, Torino, at a depth of 70 m water equivalent to reduce the cosmic-ray background level. To measure γ-activity in meteorites we have set up a highly efficient and selective Ge−NaI(Tl) γ-ray spectrometer surrounded by a passive shield. The solar modulation affects the intensity of GCR and therefore the isotopes production rates in meteorites. The 11 y solar cycle is well reproduced by the variations of²²Na (T _1/2=2.6 y) in meteorites which fell during the past three solar cycles. The⁴⁴Ti (T _1/2=66.6 y) activity measured in eight chondrites which fell in the last 110 y is qualitatively consistent with the century-scale solar-activity variation, called the Gleissberg cycle. The increase is roughly four times higher, than expected (about 5%) for a GCR flux calculated by a model in which the solar-activity modulation is determined solely by the sunspot number indexR. This result suggests a much weakened modulation of GCR during the prolonged Gleissberg minimum during which highly ordered magnetic fields set up in the heliosphere.     

On the characteristics of solar activity and galactic cosmic ray intensity at the solar cycle maximum and inflection points

The correlation between the characteristics (sunspot area and galactic cosmic ray intensity) at inflection points and at the solar cycle maximum is discussed. Probable characteristics in the forthcoming maximum of cycle 24 are considered.     

On the Acceleration of Energetic Cosmic Particles by Electrostatic Double Layers

The capability of electrostatic double layers of accelerating charged particles to high energies is investigated. Starting from a one-dimensional relativistic double-layer model a two-dimensional relativistic double layer in a current filament is studied. It is found that the filamentary double layer has a maximum potential drop that depends both on the magnitude of the filamentary current and on the composition of the layer. The results are applied to two cosmic double layers?one in a solar electric circuit and another in a galactic circuit. If the layers are composed of protons and electrons, these particles may be accelerated to 1011 eV in the solar layer and to 1014 eV in the galactic layer. It is suggested that the solar double layer may account for the acceleration of solar cosmic rays while the galactic layer may contribute to the generation of cosmic radiation.