Solar modulation of galactic cosmic rays. II
Galactic cosmic ray solar modulation in interplanetary medium, discussing spherically symmetric model
Fisk, L. A.↗
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Solar sources and the cosmic ray transport equation
Cosmic ray transport equation for solar sources, using Fisk numerical method by applying transformation of independent variable U/r,T/
Gleeson, L. J.↗
Cosmic-ray exposure history of North Ray and South Ray material
Cosmic-ray exposure ages for two breccias, 68815 and 69935, in the vicinity of South Ray Crater give consistent values of 2.0 plus or minus 0.2 m.y. when measured by the Kr-81-Kr, Na-22-Ne, and particle track methods. These also agree with estimates of exposure ages made by others using microcrater counts on six rocks in the same vicinity, including 69935. It is likely that this represents the age of South Ray Crater. Soils from stations close to South Ray Crater appear to be mature, well-irradiated materials containing little, if any, of a 2 m.y. component. Reviewing various lines of evidence, it is concluded that there are no compelling reasons to believe that so-called South Ray soils contain a large fraction of South Ray ejecta. However, if they do contain such ejecta, this material must have been well irradiated in situ prior to being thrown out in the South Ray event. A chip from a large boulder on the rim of North Ray Crater gives a Kr-81-Kr age of 50.6 plus or minus 3.8 m.y. Similar ages are found by the Na-22-Ne and the particle track methods. The agreement of this result with other data on large North Ray boulders fixes the age of North Ray Crater as 50 m.y.
Behrmann, C.↗
The Skylab ultraheavy cosmic ray experiment
Cosmic-ray nuclides of charge Z from 65 to 110 were detected with a Lexan sheet array mounted on the spacecraft. The charge distribution showed 83 nuclei of Z not less than 65, 6 nuclei of charge not less than 90, one with Z not less than 93, and no superheavy nuclei (Z not less than 110). Measured Pb/Pt and U/Pt abundance ratios are examined for information on a possible r-process, on solar system abundances, and on the time and time scale of the related nucleosynthesis events. The resolution of the experiment is deemed adequate to rule out the presence of superheavy nuclei. Experimental procedures, statistical treatment, and correlation with balloon data are discussed.
Price, P. B.↗
Further observations of geomagnetically forbidden cosmic ray nuclei
Cosmic-ray particles with kinetic energies well below cutoff values were detected during a high-altitude balloon flight at 41 deg N geomagnetic latitude. These particles had kinetic energies up to 400 MeV/amu and charges in the range from 6 to 30. They are probably reentrant albedo particles and are of interest primarily because they can be confused with fast ultraheavy primary particles in some experiments.
Friedlander, M. W.↗
The source abundances of galactic cosmic rays
The galactic cosmic ray source abundances have been determined from two complete datasets, one at low and the other at high energy. For both exponential and truncated exponential pathlength distributions (PLD), the two sets of source abundances show significant differences for the primary elements, i.e., the Fe/O ratio. An energy dependent PLD reduces but does not eliminate the discrepancy, and this may indicate an energy dependence in the source composition. New source abundances for Na, P, Cl, Ca, and Mn are derived.
Dwyer, R. D.↗
Active-Pixel Cosmic-Ray Sensor
Cosmic-ray sensor comprises planar rectangular array of lateral bipolar npn floating-base transistors each of which defines pixel. Collector contacts of all transistors in each row connected to same X (column) line conductor; emitter contacts of all transistors in each column connected to same Y (row) line conductor; and current in each row and column line sensed by amplifier, output of which fed to signal-processing circuits.
Fossum, Eric R.↗
Upper limits on the cosmic neutrino background from cosmic rays
Extragalactic and galactic cosmic rays scatter with the cosmic neutrino background during propagation to Earth, yielding a flux of relic neutrinos boosted to larger energies. If an overdensity of relic neutrinos is present in galaxies, and neutrinos are massive enough, this flux might be detectable by high-energy neutrino experiments. For a lightest neutrino of mass 𝑚 𝜈 ∼0.1 eV, we find an upper limit on the local relic neutrino overdensity of ∼10 13 and an upper limit on the relic neutrino overdensity at TXS 0506 + 056 of ∼10 10 . Future experiments like GRAND or IceCube-Gen2 could improve these bounds by orders of magnitude.
Astronomy & Astrophysics↗
A simulation of high energy cosmic ray propagation 2
The cosmic ray propagation in the Galactic arm is simulated. The Galactic magnetic fields are known to go along with so called Galactic arms as a main structure with turbulences of the scale about 30pc. The distribution of cosmic ray in Galactic arm is studied. The escape time and the possible anisotropies caused by the arm structure are discussed.
Honda, M.↗
Radiative Energy Loss by Galactic Cosmic Rays
Interactions between galactic cosmic rays and matter are a primary focus of the NASA radiation problem. The electromagnetic forces involved are for the most part well documented. Building on previous research, this study investigated the relative importance of the weak forces that occur when a cosmic ray impinges on different types of materials. For the familiar electromagnetic case, it is known that energy lost in the form of radiation is more significant than that lost via contact collisions the rate at which the energy is lost is also well understood. Similar results were derived for the weak force case. It was found that radiation is also the dominant mode of energy loss in weak force interactions and that weak force effects are indeed relatively weak compared to electromagnetic effects.
Ahern, Sean C.↗
The large scale dynamics of the outer heliosphere and the long-term modulation of galactic cosmic rays
The network of cosmic ray observatories reaching across the heliosphere has given new insight into the process of solar modulation, establishing that the decreases occur principally in the outer heliosphere and are produced by interplanetary flow systems; that the hysteresis effects appear to be produced by changes in the rigidity dependence of the diffusion coefficient and that the predicted effects on the cosmic ray gradients associated with the reversal of the solar magnetic field polarity are not observed.
Mcdonald, F. B.↗
Cosmic ray hazards in the solar system.
Cosmic ray hazards in solar system considered from measurements of cosmic ray energy and charge spectra near Earth and in interplanetary space near Earth, together with interaction of cosmic rays with Moon surface
COSMIC RADIATION↗
Supernova remnants and the interstellar medium - Constraints from cosmic-ray acceleration
The reacceleration rate of cosmic rays by supernova (SN) remnants is calculated and expressed in terms of the parameters determining the cosmic ray model and the SN expansion. It is shown that the constraint on reacceleration derived from the B/C data leads to constraint on the expansion of SN remnants in the ISM and on the effective density of ISM. The effect of cloud evaporation is estimated and the expansion rate of supernova remnants, cosmic ray reacceleration, and the state of the ISM are solved for simultaneously. In the resulting self-consistent solution, SN remnants produce a reacceleration rate and an effective acceleration shock strength which is consistent with the values indicated by the cosmic ray data.
Wandel, A.↗
Plastic scintillators in coincidence for the study of multi-particle production of sea level cosmic rays in dense medium
Cosmic ray particles at sea level penetrate a thick layer of dense medium without appreciable interaction. These penetrating particles are identified with muons. The only appreciable interaction of muons are by knock on processes. A muon may have single, double or any number of knock on with atoms of the material so that one, two, three or more particles will come out from the medium in which the knock on processes occur. The probability of multiparticle production is expected to decrease with the increase of multiplicity. Measurements of the single, double, and triple particles generated in a dense medium (Fe and Al) by sea level cosmic rays at 22.42 N. Lat. and 114.20 E. Long. (Hong Kong) are presented using a detector composed of two plastic scintillators connected in coincidence.
Chuang, L. S.↗
New Measurements of the Li, Be, and B Isotopes as a Test of Cosmic Ray Transport Models
Precise measurements of predominantly secondary cosmic-ray Li, Be, and B together with current well-measured production cross-sections for these isotopes help to improve our understanding of galactic cosmic ray propagation models. The Cosmic Ray Isotope Spectrometer (CRIS) on ACE has been measuring isotopic composition of cosmic rays since 1997 with high statistical precision. We present the isotopic abundances from CRIS and discuss these observations in the context of cosmic-ray transport models and previous cosmic-ray measurements.
deNolfo, Georgia A.↗
Acoustic instability driven by cosmic-ray streaming
We study the linear stability of compressional waves in a medium through which cosmic rays stream at the Alfven speed due to strong coupling with Alfven waves. Acoustic waves can be driven unstable by the cosmic-ray drift, provided that the streaming speed is sufficiently large compared to the thermal sound speed. Two effects can cause instability: (1) the heating of the thermal gas due to the damping of Alfven waves driven unstable by cosmic-ray streaming; and (2) phase shifts in the cosmic-ray pressure perturbation caused by the combination of cosmic-ray streaming and diffusion. The instability does not depend on the magnitude of the background cosmic-ray pressure gradient, and occurs whether or not cosmic-ray diffusion is important relative to streaming. When the cosmic-ray pressure is small compared to the gas pressure, or cosmic-ray diffusion is strong, the instability manifests itself as a weak overstability of slow magnetosonic waves. Larger cosmic-ray pressure gives rise to new hybrid modes, which can be strongly unstable in the limits of both weak and strong cosmic-ray diffusion and in the presence of thermal conduction. Parts of our analysis parallel earlier work by McKenzie & Webb (which were brought to our attention after this paper was accepted for publication), but our treatment of diffusive effects, thermal conduction, and nonlinearities represent significant extensions. Although the linear growth rate of instability is independent of the background cosmic-ray pressure gradient, the onset of nonlinear eff ects does depend on absolute value of DEL (vector differential operator) P(sub c). At the onset of nonlinearity the fractional amplitude of cosmic-ray pressure perturbations is delta P(sub C)/P(sub C) approximately (kL) (exp -1) much less than 1, where k is the wavenumber and L is the pressure scale height of the unperturbed cosmic rays. We speculate that the instability may lead to a mode of cosmic-ray transport in which plateaus of uniform cosmic-ray pressure are separated by either laminar or turbulent jumps in which the thermal gas is subject to intense heating.
Begelman, Mitchell C.↗
Cosmic-ray transport in inhomogeneous media
A theory of cosmic-ray transport in multiphase diffusive media is developed, with the specific application to cases in which the cosmic-ray diffusion coefficient has large spatial fluctuations that may be inherently multiscale. We demonstrate that the resulting transport of cosmic rays is diffusive in the long-time limit, with an average diffusion coefficient equal to the harmonic mean of the spatially varying diffusion coefficient. Thus, cosmic-ray transport is dominated by areas of low diffusion even if these areas occupy a relatively small, but not infinitesimal, fraction of the volume. On intermediate time-scales, the cosmic rays experience transient effective subdiffusion, as a result of low-diffusion regions interrupting long flights through high-diffusion regions. In the simplified case of a two-phase medium, we show that the extent and extremity of the subdiffusivity of cosmic-ray transport is controlled by the spectral exponent of the distribution of patch sizes of each of the phases. We finally show that, despite strongly influencing the confinement times, the multiphase medium is only capable of altering the energy dependence of cosmic-ray transport when there is a moderate (but not excessive) level of perpendicular diffusion across magnetic-field lines.
Astronomy and Astrophysics↗
Solar cosmic ray propagation characteristics.
Solar cosmic ray propagation and adequacy of current models to explain modes of propagation
COSMIC RAY PROPAGATION↗