Energy Spectra Of Heavy Nuclei Research Articles

The energy spectra of heavy nuclei measured by the ATIC experiment

The preliminary energy spectra of heavy nuclei C, O, Ne, Mg, Si, and Fe in the primary cosmic rays measured by the ATIC-2 experiment are presented and compared to previous data and to propagation models. Using previous data to extend the ATIC-2 results for all heavy nuclei to higher energy, the combined spectra can be best fit with diffusion model with weak reacceleration and scattering on random magnetic field with a Kolmogorov spectrum fluctuations becoming dominant at high energy.

Observation of transition radiation from relativistic heavy nuclei.

We have made the first observation of transition radiation produced by relativistic heavy nuclei. The instrument used in this work is a large cosmic-ray detector for the space shuttle designed to measure the energy spectra of heavy nuclei in the cosmic radiation at TeV/nucleon energies. The response of the detector scales with the charge $Z$ of the primary nucleus as expected from theory. The relative fluctuations in detected transition radiation from heavy nuclei are much smaller than those from singly charged particles, because of the large number of photons produced. This makes possible an accurate determination of the energy of the nucleus in the TeV/nucleon region by measurement of the transition radiation yield. The response of such a detector can be well extrapolated from accelerator measurements with singly charged particles.

Composition and Energy Spectra of Heavy Nuclei of Unknown Origin Detected on Skylab

At the orbit of Skylab we observed steeply falling energy spectra of nuclei with $Z>~8$ and $10\ensuremath{\lesssim}E\ensuremath{\lesssim}40$ MeV/amu at intensities much higher than seen outside the magnetosphere. The composition is O: Ne: [Na-Si]: Fe = 100:33:13:(\ensuremath{\sim}2), consistent with that of the solar corona. We suggest that heavy solar-wind ions enter the magnetosphere, are accelerated, and populate the inner radiation belt.

Composition and Energy Spectra of Heavy Nuclei with 0.5 < E < 40 MeV Per Nucleon in the 1971 January 24 and September 1 Solar Flares

view Abstract Citations (36) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Composition and Energy Spectra of Heavy Nuclei with 0.5 < E < 40 MeV Per Nucleon in the 1971 January 24 and September 1 Solar Flares Crawford, H. J. ; Price, P. B. ; Sullivan, James D. Abstract Energy spectra of 0, Si, and Fe between 0.5 and 40 MeV per nucleon have been measured with stacks of plastic detectors exposed in a rocket during the 1971 January 24 flare. The Fe/Si ratio decreases from 1.8 + 0.3 to 0.42 1 0.14 with energy. In both the January 24 flare and the September 1 flare, the abundances of elements 10 < Z < 28 at 15 MeV per nucleon are similar to high-energy cosmic-ray source abundances; S, Ne, and Ar are significantly lower than current solar values. Publication: The Astrophysical Journal Pub Date: August 1972 DOI: 10.1086/181005 Bibcode: 1972ApJ...175L.149C full text sources ADS |

The Chemical Composition and the Energy Spectrum of Heavy Nuclei in the Cosmic Radiation above 10 GeV/nucleon

A total of 7695 heavy nuclei were located in the Brawley emulsion stack. The error in energy estimation was about 30% and that in charge estimation was 0.25 units of charge for nuclei with z ≤9 and 0.5 for the iron group. The flux values for respective charge groups at the top of the atmosphere at energies above 10 GeV/nucleon are J M 0 =0.686±0.117, J H 0 =0.241±0.032, J LH 0 =0.166±0.022, J MH 0 =0.015±0.004 and J VH 0 =0.060±0.012, particles/m 2 ·sec·sterad. The integral energy spectra of the individual charge groups have the same exponent of γ=1.60 up to several hundreds of GeV/nucleon. On the basis of the experimental results in the present investigation, the mechanisms of cosmic ray acceleration and the amount of matter traversed by the cosmic rays are discussed.

Cosmic ray nuclei of chargeZ⩾3 during the period of low solar activity

A detailed study of the composition and energy spectra of heavy nuclei of charge Z⩾3 in the primary cosmic rays has been made during the period of low solar activity, using two stacks of nuclear emulsions exposed in balloon flights from Fort Churchill, Canada, in June 1963. Each of the stacks was composed of 120 nuclear emulsions of three different sensitivities and was exposed at about 3·5 g. cm.−2 of residual air for about 11.1 hr. Reliable resolution of charges of nuclei from lithium to oxygen was obtained; for heavier nuclei, charge groups were determined. From the analysis of 793 tracks of nuclei with Z⩾3, results on the following aspects were obtained: The implications of these results are discussed.

The energy spectrum of heavy nuclei above 10 GeV/nucleon

An experimental observation is made of the energy spectrum of heavy nuclei in the primary cosmic radiation using a large emulsion stack. The preliminary data so far accumulated indicate an exponent of 1.60 to 1.65 for the integral total-energy-per-nucleon spectrum.

Charge and Energy Spectrum of Heavy Nuclei during the Solar Minimum, 1965

The differential energy spectra of ${H}_{1}$ ($Z\ensuremath{\ge}20$) and $H$ ($Z\ensuremath{\ge}10$) nuclei were measured in a balloon flight at a time close to the solar minimum using a nuclear emulsion stack flown at an altitude of 2.7 g/${\mathrm{cm}}^{2}$ from Fort Churchill, Manitoba, Canada on 30 June 1965. $\ensuremath{\delta}$-ray density and residual range measurements on tracks, and measurements of change of $\ensuremath{\delta}$-ray density with track length, were used to determine the charge and energy of the nuclei. The measured differential fluxes of ${H}_{1}$ ($Z\ensuremath{\ge}20$) and $H$ ($Z\ensuremath{\ge}10$) nuclei are 0.0013\ifmmode\pm\else\textpm\fi{}0.0006 and 0.0045\ifmmode\pm\else\textpm\fi{}0.0010 particles/(${\mathrm{m}}^{2}$ sr sec MeV per nucleon) in the energy range 300-500 MeV per nucleon and 0.0011\ifmmode\pm\else\textpm\fi{}0.0004 and 0.0049\ifmmode\pm\else\textpm\fi{}0.0008 particles/(${\mathrm{m}}^{2}$ sr sec MeV per nucleon) in the energy range 500-800 MeV per nucleon. These results are in agreement with satellite and rocket measurements made in the similiar energy range, and, when compared with low-energy measurements, indicate an energy spectrum of nucle that is flatter than those observed during earlier years.

Steady State of Cosmic-Ray Nuclei—Their Spectral Shape and Path Length at Low Energies

The steady state of cosmic-ray nuclei in interstellar space is discussed. It is shown that for a steady-state situation (or for any mode of propagation in which the allowed path lengths between the source and observer have a wide distribution), the generally used matter-slab approximation for the interstellar matter traversed by cosmic rays leads to erroneous conclusions. The steady-state energy spectra of heavy nuclei are found to have negative slopes down to energies $\ensuremath{\sim}50 \frac{\mathrm{MeV}}{N}$, if the injection spectra are like a rigidity power law; this offers an explanation for the apparently surprising observation of flat spectra for heavy nuclei down to energies $\ensuremath{\sim}50 \frac{\mathrm{MeV}}{N}$. Further it is found that the $\frac{L}{M}$ ratio cannot keep on increasing at low energies but must decrease continuously below a few hundred $\frac{\mathrm{MeV}}{N}$, even for energy-independent fragmentation cross sections; this also is in accord with recent experimental results.

The energy spectrum of cosmic-ray heavy nuclei of chargeZ≥10 during a solar quiet time in July 1961

The energy spectrum of heavy nuclei (charge Z≥10) has been determined, in the energy interval from 200–700 Mev/nucleon, using a stack of nuclear emulsions, exposed on July 8, 1961, at a mean altitude of ∼2.4 g/cm2 of residual atmospheric depth on a balloon flown from Fort Churchill, Manitoba. The flight was preceded by a period of three months of low solar and geophysical activity. The charge and energy spectra were obtained principally from tracks of particles that ended in the detector by a combination of range and δ-ray density measurements. A second charge estimation for particles that stop in the emulsion was made from integral δ-ray counts as a function of range. The energy spectrum was measured up to 700 Mev/nucleon by also taking into consideration the tracks that pass through or interact within the stack using a combination of δ-ray density and multiple scattering measurements that determine the charge and energy of the nuclei. This energy spectrum was combined with the spectra measured for protons and helium nuclei in the same flight and with similar data obtained during 1963 with a view of arriving at a better understanding on the propagation of cosmic-ray nuclei in source regions, instellar space, and solar system.

The composition and energy spectrum of low-energy heavy nuclei of the primary cosmic rays in June 1963

Recently three investigations have been reported on the flux and energy spectrum of low-energy heavy nuclei of the primary cosmic radiation measured during the middle of 1963 [Lim and Fukui, 1965; Webber et al., 1966; and Fichtel et al., 1966]. Of these the last investigation refers to energies <200 Mev/nucleon only; the results of Lim and Fukui [1965] and Webber et al. [1966] on the spectral shape of M nuclei, (6 ≤ Z ≤ 9) are in disagreement with one another, since the former observed the peak in the energy spectrum of M nuclei at 150–200 Mev/nucleon and the latter at 400–500 Mev/nucleon. Since the shape and the position of the peak of the differential spectrum during the period near solar minimum is of much importance in studying the interplanetary and interstellar modulation of the primary radiation, it becomes necessary to resolve this disagreement. For this purpose we present briefly in this note our final results on the flux and energy spectrum of heavy nuclei in the middle of 1963.

Energy Spectrum of Heavy Nuclei of the Primary Cosmic Radiation during Solar Maximum

The energy spectrum of nuclei with $Z&gt;~13$ has been determined using the knock-on electron method in a stack of nuclear emulsions flown on 4 February 1959 from Texas, U.S.A. ($\ensuremath{\lambda}=41$\ifmmode^\circ\else\textdegree\fi{}N). In the interval of kinetic energy from 1.5 to 10 GeV/nucleon, the exponents of the integral energy spectra for nuclei with charge $Z&gt;~13$, $13&lt;~Z&lt;~16$ and for those with $Z&gt;~17$ have been determined to be 1.70\ifmmode\pm\else\textpm\fi{}0.30, ${1.85}_{\ensuremath{-}0.20}^{+0.23}$, and ${1.55}_{\ensuremath{-}0.30}^{+0.20}$, respectively. From this and other similar experiments it is surmised that within the experimental uncertainties the observations are consistent with the assumption that the energy spectra of all the components of the primary cosmic radiation have the same exponent; also the exponent seems to be the same during solar minimum and during solar maximum. The flux of nuclei with $Z&gt;~10$ has been obtained as 1.26\ifmmode\pm\else\textpm\fi{}0.09 particles/${\mathrm{m}}^{2}$ sec sr and that of nuclei with $Z&gt;~20$ as 0.39\ifmmode\pm\else\textpm\fi{}0.06 particle/${\mathrm{m}}^{2}$ sec sr. These values are \ensuremath{\sim}50% lower than those determined over Texas during solar minimum.

Evidence for a Forbush Type of Decrease in the Intensity of Heavy Nuclei of the Primary Cosmic Radiation

In an emulsion stack flown on March 13, 1956 from Iowa, the flux of heavy nuclei with $Z\ensuremath{\ge}6$ in the primary cosmic radiation was measured as 15.8\ifmmode\pm\else\textpm\fi{}1.0 and 3.7\ifmmode\pm\else\textpm\fi{}0.6 particles/${\mathrm{m}}^{2}$ sec sr for particles of kinetic energy \ensuremath{\ge}0.23 and \ensuremath{\ge}1.55 Bev/nucleon, respectively. The measured flux of energy \ensuremath{\ge}1.55 Bev/nucleon was 57\ifmmode\pm\else\textpm\fi{}11% lower than the normal flux. It is shown that almost the entire part of the reduction must be attributed to a large Forbush decrease of the cosmic radiation that occurred at the same time. The exponent of the integral energy spectrum of heavy nuclei ($Z\ensuremath{\ge}6$) was measured as 1.78\ifmmode\pm\else\textpm\fi{}0.24 in the energy interval 0.23 to 9 Bev/nucleon. As this value is not significantly different from its normally measured value, it appears that the large reduction in the primary flux was not accompanied by any significant change in the energy spectrum.

Heavy Nuclei in the Primary Cosmic Radiation at Prince Albert, Canada. I. Carbon, Nitrogen, and Oxygen

A stack of G-5 emulsion, exposed at 120 000 feet for 8 hours at 61\ifmmode^\circ\else\textdegree\fi{}N has been used to study the charge and energy spectrum of heavy nuclei at the low-energy end. Energy measurements have been made on C, N, and O nuclei up to 1 Bev/nucleon. The spectrum shows a broad maximum at 550 Mev/nucleon, extrapolated to the top of the atmosphere. Various possibilities to explain this spectrum are discussed. However, it seems desirable to determine the energy spectrum of the other heavy-nuclei components in this energy region in order to gain a more complete understanding of the whole problem. Measurements of this kind are in progress and will be reported.

On the Energy Spectrum of Heavy Nuclei in Primary Cosmic Radiation

On the Energy Spectrum of Heavy Nuclei in Primary Cosmic Radiation