Energy dependence of cosmic ray composition above 10(15) GeV/nucleus

It is argued that above 10 to the 5th power GeV/nucleus, in the range where charge-resolved spectra have not yet been determined, the appropriate measures of equal-energy composition are 1nA and 1nA , the mean value and dispersion relative to the mean value and dispersion relative to the mean of 1nA, where A is the mass number. Experimental data which are sensitive to changes in 1nA with increasing energy are examined. It is found that, taken as a whole, they show no change (+ or 0.5) between 10 to the 5th power and 10 to the 6th power GeV, and a decrease of 1.5 + or - 0.5 between 10 to the 6th power and 10 to the 8th power GeV, with no further change + or - 0.5) above 10 to the 8th power GeV. Taken as a whole, the various indirect estimates of the absolute value of 1nA above 10 to the 5th power GeV/nucleus are also consistent with this pattern. For a wide range of astrophysically plausible composition models the value of the other measure, 1nA is insensitive to changes in 1nA . Because of this the existing data on 1nA can likewise easily be reconciled with this pattern

Implications of the experimental results on high energy cosmic rays with regard to their origin

It was shown in an earlier report that current cosmic ray evidence supports a change in the cosmic ray composition in the region between 10 to the 6th power and 10 to the 8th power GeV total energy in the direction of a smaller average value of A. Compared to normal celestial abundances, the heavy nuclei are much less abundant, and, in fact, the composition measurements above 10 to the 8th power GeV are consistent with there being only protons. Here, these results combined with those of the energy spectrum and anisotropy of the comsic rays and other astrophysical information will be examined to try to determine their implications for the origin of the cosmic rays. In this paper, consideration is given to the implications of one or more than one type of source in the galaxy to see which are consistent with the interpretation of current measurements. The nature of the source types that would be required are discussed

Diffuse gamma radiation

An examination of the intensity, energy spectrum, and spatial distribution of the diffuse gamma-radiation observed by SAS-2 satellite away from the galactic plane in the energy range above 35 MeV has shown that it consists of two components. One component is generally correlated with galactic latitudes, the atomic hydrogen column density was deduced from 21 cm measurements, and the continuum radio emission, believed to be synchrotron emission. It has an energy spectrum similar to that in the plane and joins smoothly to the intense radiation from the plane. It is therefore presumed to be of galactic origin. The other component is apparently isotropic, at least on a coarse scale, and has a steep energy spectrum. No evidence is found for a cosmic ray halo surrounding the galaxy in the shape of a sphere or oblate spheroid with galactic dimensions. Constraints for a halo model with significantly larger dimensions are set on the basis of an upper limit to the gamma-ray anisotropy

Exploratory Meeting on Airborne Doppler Lidar Wind Velocity Measurements

The scientific interests and applications of the Airborne Doppler Lidar Wind Velocity Measurement System to severe storms and local weather are discussed. The main areas include convective phenomena, local circulation, atmospheric boundary layer, atmospheric dispersion, and industrial aerodynamics

Non-association of a celestial gamma ray source with the new Milky Way satellite galaxy

The newly discovered satellite galaxy located in the Milky Way galactic anti-center region is discussed along with the possibility that a nearby gamma ray source is associated with it. The factors which led to the conclusion that the gamma ray excess is not associated with the galaxy are considered

The relationship between the galactic matter distribution, cosmic ray dynamics, and gamma ray production

Theoretical considerations and analysis of the results of gamma ray astronomy suggest that the galactic cosmic rays are dynamically coupled to the interstellar matter through the magnetic fields, and hence the cosmic ray density should be enhanced where the matter density is greatest on the scale of galactic arms. This concept has been explored in a galactic model using recent 21 cm radio observations of the neutral hydrogen and 2.6 mm observations of carbon monoxide, which is considered to be a tracer of molecular hydrogen. The model assumes: (1) cosmic rays are galactic and not universal; (2) on the scale of galactic arms, the cosmic ray column (surface) density is proportional to the total interstellar gas column density; (3) the cosmic ray scale height is significantly larger than the scale height of the matter; and (4) ours is a spiral galaxy characterized by an arm to interarm density ratio of about 3:1

SAS-2 observations of gamma rays from the galactic plane

The SAS-2 gamma ray experiment has made measurements on the high energy gamma rays coming from the galactic center region. The gamma radiation in this region is very much more intense than in the anticenter region, in agreement with the observations made with the OSO-3 experiment of Kraushaar et al. (1973); and exhibits a narrow distribution along the plane which is nearly uniform in intensity from 330 deg to 30 deg. The energy spectrum in the range from 35 MeV to 210 MeV is quite flat, consistent with a cosmic ray-interstellar matter interaction pion-decay spectrum, or a mixture of this spectrum and a spectrum formed by Compton radiation from cosmic ray electrons. The intensity of the radiation in the anticenter direction is consistent with that expected from the cosmic ray-interstellar matter interaction origin, namely 0.000.002 photons

SAS-2 High energy gamma-ray observations of the Vela pulsar

The second Small Astronomy Satellite high-energy (35 MeV) gamma-ray telescope detected pulsed gamma-ray emission at the radio period from PSR 0833-45, the Vela pulsar, as well as an unpulsed flux from the Vela region. The pulsed emission consists of two peaks, one following the radio peak by about 13 msec, and the other 0.4 period after the first. The luminosity of the pulsed emission above 100 MeV from Vela is about 0.1 that of the pulsar NP0532 in the Crab nebula, whereas the pulsed emission from Vela at optical wavelengths is less than 0.0004 that from the Crab. The relatively high intensity of the pulsed gamma-ray emission and the double peak structure, compared to the single pulse in the radio emission, suggests that the high energy gamma-ray pulsar emission may be produced under different conditions from those found at lower energies

High energy galactic gamma radiation from cosmic rays concentrated in spiral arms

A model for the emission of high energy ( 100 MeV) gamma rays from the galactic disk was developed and compared to recent SAS-2 observations. In the calculation, it is assumed that (1) the high energy galactic gamma rays result primarily from the interaction of cosmic rays with galactic matter; (2) on the basis of theoretical and experimental arguments the cosmic ray density is proportional to the matter density on the scale of galactic arms; and (3) the matter in the galaxy, atomic and molecular, is distributed in a spiral pattern consistent with density wave theory and the experimental data on the matter distribution

SAS-2 observations of the galactic gamma radiation from the Vela region

Data from a scan of the galactic plane by the SAS-2 high energy gamma ray experiment in the region 250 deg l2 290 deg show a statistically-significant excess over the general radiation from the galactic plane for gamma radiation of energy 100 MeV in the region 260 deg l2 270 deg and -7.5 deg b2 0 deg. If the enhanced gamma radiation results from interactions of cosmic rays with galactic matter, as the energy spectrum suggests, it seems reasonable to associate the enhancement with large scale galactic features, such as spiral arm segments in that direction, or with the region surrounding the Vela supernova remnant, with which PSR 0833-45 is associated. If the excess is attributed to cosmic rays released from this supernova interacting with the interstellar matter in that region, then on the order of 3.10 to the 50th power ergs would be released by that supernova in the form of cosmic rays