Composition of solar cosmic rays

Summary The general features of the solar particle composition now seem to be clear. The two most abundant components, protons and helium nuclei, have different velocity spectra, similar, but not exactly identical rigidity spectra, and varying relative abundances. The multiply charged nuclei, on the other hand, appear to have the same spectral shape and relative abundances each time measurements are made, at least in the region from 42 to 135 MeV/nucleon. Further, these relative abundances seem to reflect those of the solar atmosphere insofar as comparison can be made. Electrons are rare, but high energy electrons are not expected to be plentiful due to the probable high rate of energy loss caused by synchrotron radiation at the sun. Energetic neutrons were also not expected in large quantity and have not been observed. Finally, there is positive evidence that very small quantities of deuterons exist, probably in an amount which is about 10^-3 or less of the proton abundance.The experimental data indicate that the propagation phenomenon is not purely rigidity dependent. Although the propagation of solar particles is still not well understood, the development of theories which take into account both the general magnetic field and the inhomogeneities in the field seem to hold some promise of explaining the experimental results. The composition data have also established important restraints which any acceleration theory must satisfy, and thereby contributed greatly to the very difficult problem of determining the acceleration mechanism.The similarity of the relative abundance of the energetic solar particles and the nuclei in the sun's photosphere suggested the possibility of having a new means of estimating the solar neon and helium abundances. This very interesting possibility will have to be explored by further testing of the composition of future solar particle events. Finally, it was seen that the composition was a very strong argument against most stars being the principal source of high energy non-solar cosmic rays, and, therefore, special sources, such as supernovae or possibly quasistellar objects, should be considered as much more likely prospects for the origin of cosmic rays.The results which have been obtained thus far on the composition of solar cosmic rays have indicated that further research in this area of study should be very rewarding and of value to many fields of physics. Further data on the composition and relative, as well as absolute, energy spectra of the various components are needed throughout many events. More experiments also should be performed to determine the properties of the rare components, deuterons, tritons, He³ nuclei, electrons, neutrons, and the heavier nuclei. When these experiments are complete, the knowledge which is needed to aid in answering the solar and astrophysical problems discussed in this review should be at hand.     

Oxygen line mapping of SN 1006 with Suzaku

SN 1006 is one of the supernova remnants (SNRs) with relatively low-temperature electrons, considering the young age of just 1000 years. We carried out SN 1006 mapping observations with the X-ray Imaging Spectrometers (XIS) and the Hard X-ray Detector (HXD) onboard Suzaku, the fifth Japanese X-ray satellite. Thanks to the excellent spectral resolution of XIS in the soft X-ray band, H-like and He-like oxygen emission lines were clearly detected, and we could make a map of the line intensity, and as well as a flux and the photon index of nonthermal component. We found that these parameters have spatial dependences from region to region in the SNR; the north region is bright in nonthermal, while dim in thermal; the east region is bright in both nonthermal and thermal; the inner region shows dim nonthermal and bright thermal emission. The photon index is the smallest in the north region.     

Dynamics of Planetary Waves in the Ionosphere as Observed from GPS Satellites

The GPS satellite data are used to study the dynamics of the ionospheric total electron content (TEC) over Central Europe in the summer season from June 23 to September 30, 1996. The TEC variations within the range of periods typical of the planetary waves were found to be nearly synchronous with the neutral wind variations in the mesosphere and with the variations in the occurrence of ionospheric sporadic layers. The observed TEC variations were interpreted as the result of penetration of energy carried by nonstationary Rossby waves to the upper atmospheric altitudes.     

Postmission plasma volume and red-cell mass changes in the crews of the first two Skylab missions

Red-cell mass determinations were performed before and after the first two Skylab missions. The data showed a 14% mean decrease in red-cell mass after the 28-day mission and a 12% mean decrease after the 59-day mission. The red-cell mass returned to premission levels more slowly after the shorter (28-day) than after the longer mission. Plasma volume decreases were found after each mission. with the crew from the longer mission showing the greater change (13% vs. 8.4%). Postmission decreases in red-cell mass and plasma volume have been a general finding in crewmen who return from short or long spaceflight.