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.     

Quasiperiodic Variations of Solar Activity and Cosmic Rays

Quasiperiodic variations of various manifestations of solar activity, parameters of the interplanetary medium, and the flux of galactic cosmic rays (GCRs) are studied using the data of stratospheric sounding and measurements with neutron monitors. Groups of spectral components with periods of ~2, 1.3, and ~1 year are identified in the range of periods shorter than 5 years. Particular attention is paid to quasi-2-year GCR variations that are induced by similar variations of the mean magnetic field of the Sun and are integral to the processes of solar activity.     

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.     

“Meander”-like and “slit”-like variations in the flux of solar cosmic rays

Results of studying the origin of “meander”-like and “slit”-like variations in fluxes of solar cosmic rays (SCR) are presented as exemplified by the events that occurred on March 19, 1990 and December 14–15, 2006. Experimental data that were obtained by the GRANAT, ACE, Wind, STEREO-A, and STEREO-B spasecrafts are used. The analysis is based on the data of observations of dynamic structures in the solar atmosphere and their continuation in the heliosphere, as well as on an empirical “reflection” model of the movement, accumulation, and modulation of cosmic rays. A structural source of these variations on the Sun is discussed, which is shaped as discrete magnetic plasma loops and arches located between active regions. Such structures in the form of magnetic-plasma tubes transferred from the chromosphere and corona and filled with SCR rotate together with the Sun and, when crossing the detector location region, cause space-time variations in meander-like and slit-like variations in SCR.     

Spectrum and mechanism of the acceleration of protons in a solar flare

Investigations based on neutron monitor data show that two components of relativistic cosmic rays are generated by a solar flare. The so-called prompt component comes from a flare with flight times and is characterized by an exponential spectrum with a parameter of E ₀ ≈ 0.5 Gev. Numerical simulation of the conditions in the flare current sheet of the Bastille flare demonstrated that such a spectrum is formed at a magnetic reconnection velocity of ∼10⁷ cm s⁻¹. The delayed component has a power law spectrum and is apparently formed during the diffusion of protons in the plasma of the interplanetary magnetic field.     

Combined mechanisms of solar cosmic ray acceleration

Spectra of solar cosmic rays on the Sun’s surface at a flare site and near Earth are modeled using the Monte Carlo method. Two of the most important mechanisms of energy accumulation by the particles are considered simultaneously: the regular acceleration of ions by the impulsive electric field of the current sheet and stochastic acceleration by the Alfvenic turbulence. This leads to substantial variations in the particle spectra in the low-energy region.     

Transparency of a magnetic cloud boundary for cosmic rays

A magnetic cloud model is proposed in the form of a torus with a characteristic type of magnetic field (a flux rope) located inside an interplanetary coronal mass ejection propagating away from the Sun into interplanetary space. The magnetic field in the torus is determined. The transparency of the magnetic cloudsolar wind boundary is calculated for cosmic rays with different energies.     

Diffusion of charged particles in strong large-scale random and regular magnetic fields

The nonlinear collision integral for the Green’s function averaged over a random magnetic field is transformed using an iteration procedure taking account of the strong random scattering of particles on the correlation length of the random magnetic field. Under this transformation the regular magnetic field is assumed to be uniform at distances of the order of the correlation length. The single-particle Green’s functions of the scattered particles in the presence of a regular magnetic field are investigated. The transport coefficients are calculated taking account of the broadening of the cyclotron and Cherenkov resonances as a result of strong random scattering. The mean-free path lengths parallel and perpendicular to the regular magnetic field are found for a power-law spectrum of the random field. The analytical results obtained are compared with the experimental data on the transport ranges of solar and galactic cosmic rays in the interplanetary magnetic field. As a result, the conditions for the propagation of cosmic rays in the interplanetary space and a more accurate idea of the structure of the interplanetary magnetic field are determined.     

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.     

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.     

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.     

Solar Flare Activity from 2006 to 2016 according to Data from the PAMELA and ARINA Spectrometers

In the period from 2006 to 2016, experiments based on the use of the PAMELA and ARINA spectrometers and aimed at detecting cosmic rays were performed on board the RESURS-DK1 satellite. Although the main goal of these experiments was to study the galactic component of cosmic rays, the instruments in question also detected, over a broad energy range, solar particles accelerated in powerful explosive processes on the Sun (solar flares). A list of solar events in which the PAMELA and ARINA spectrometers detected, in various years of their operation, an increase in the intensities of fluxes of solar protons whose energies were above 45 MeV is presented among other things.     

Features of cosmic ray variation at the phase of the minimum between the 23rd and 24th solar cycles

The minimum between the 23rd and 24th cycles of solar activity was unusually deep and extended. The modulation of cosmic rays was minimal for the more than 70-year-long period of direct measurements. The data from stratospheric measurements by the Lebedev Physical Institute suggest that the flux of cosmic rays with more than 100 MeV/nucleon of energy exceeded the highest ever observed level (May 1965) by almost 12%. However, the ground-based neutron monitors sensitive to relatively high energies indicated that the flux of cosmic rays increased by less than 3%. This work compares the variations in the cosmic rays over periods of five minima of solar activity (the 20th to the 24th cycle). It is shown that in late 2008, an extra flux of particles with energies less than several GeV/nucleon was detected in the Earth’s orbit. A similar (though far smaller in scale) phenomenon was also observed in 1987 at the same orientation of the Sun’s magnetic field A < 0, but was not observed in epochs where A > 0.     

Heliospheric modulation of high-energy cosmic rays: II. Deformation of the neutral surface

Analysis of neutron monitor data in the periods of negative and positive polarities of the general solar magnetic field has revealed a dependence of the long-term cosmic-ray modulation on both deformation of the neutral surface of the interplanetary magnetic field and solar activity level. The effects of solar activity and neutral surface deformation dominate at positive and negative polarities, respectively. The magnetic drift of cosmic rays with different trajectories in the epochs of positive and negative polarities is responsible for this behavior of the 11-year and annual density modulations.     

Variation of the cosmic ray intensity in an 11-yr solar activity cycle: Experiment and theory

To study long-term variations of the cosmic ray intensity in a wide energy range, a basic model of the modulation of cosmic rays in the heliosphere has been developed at the Institute of Cosmophysical Research and Aeronomy, Siberian Branch, Russian Academy of Sciences. The model involves only one free modulation parameter, the ratio of the regular magnetic field to the turbulent field. It can be used to describe variations of the cosmic ray intensity in a wide energy range of 0.1 to 100 GeV. Attempts have been made to most correctly describe the features of the behavior of the cosmic ray intensity in several solar activity cycles.     

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)     

Ionization states of cosmic rays:Anuradha (IONS) experiment in Spacelab-3

The measurements of the ionization states, composition, energy spectra and spatial distribution of heavy ions of helium to iron of energies 10–100 MeV/amu in the anomalous cosmic rays are of major importance in understanding their origin which is unknown at present.Anuradha (IONS) cosmic ray experiment in Spacelab-3 was designed to determine the above properties in near earth space and this had a highly successful flight and operations aboard the shuttle Challenger at an orbital altitude of 352 km during 29 April to 6 May 1985. The instrument employs solid state nuclear track detectors (CR-39) of high sensitivity and large collecting area of about 800 cm² and determines the arrival time information of particles with active elements. Experimental methods, flight operations and preliminary results are briefly described. Initial results indicate that relatively high fluxes of low energy cosmic ray α-particles, oxygen group and heavier ions were obtained. The flight period corresponded to that of quiet Sun and the level of solar activity was close to solar minimum. It is estimated that about 10,000 events of low energy cosmic ray alpha particles with time annotation are recorded in the detector together with similar number of events of oxygen and heavier ions of low energy cosmic rays. The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion.     

Pointlike gamma ray sources as signatures of distant accelerators of ultrahigh energy cosmic rays

We discuss the possibility of observing distant accelerators of ultrahigh energy cosmic rays in synchrotron gamma rays. Protons propagating away from their acceleration sites produce extremely energetic electrons during photopion interactions with cosmic microwave background photons. If the accelerator is embedded in a magnetized region, these electrons will emit high energy synchrotron radiation. The resulting synchrotron source is expected to be pointlike, steady, and detectable in the GeV-TeV energy range if the magnetic field is at the nanoGauss level.     

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