ALBERT

Description: A brief note is summarized to show the importance of solar neutron observations for the advancement of phenomena crucial for solar physics, and to suggest the constraints which must be placed on the Solar Probe Mission for carrying out studies of this kind.

Description: The analysis of magnetic field and nuclei measurements in the 1 to 10 MeV/nucleon range for protons and helium at about 16 deg N solar latitude near solar cycle minimum (1975-76) shows both: (1) that nucleons are accelerated locally in corotating shocks, and (2) that the associated recurring corotating interaction regions (CIRs) at about 16 deg latitude have approximately the same temporal and spatial parameters found for CIRs in the equatorial plane at radial distances less than 5 AU. The evidence indicates that both the CIR structures and nucleon acceleration by shocks extend to intermediate solar latitudes and are likely to be observed during the Ulysses Mission out of the ecliptic plane.

Description: In the period 1980-84, observations of relativistic and low energy (30 E 70 MeV/n) cosmic ray nuclei from Pioneer 10 in the outer heliosphere and from IMP-8 at AU show that increases as well as decreases in intensity propagate outward at velocities equal to or greater than the average solar wind velocity.

Description: As a continuation of the program of solar modulation studies, new measurements were carried out with the cosmic ray telescope on the Earth satellite IMP-8, of the intensity time variations and the energy spectra of galactic cosmic ray protons, helium, carbon and oxygen from 1980 through 1984 including the recent solar maximum. In order to test the applicability of a steady state model of solar modulation during a period which includes times of rapidly changing modulation, these fluxes were equated with the predictions of a conventional model of solar modulation which assumes equilibrium between modulation mechanisms. It is found that for a reasonable range of variations of the diffusion coefficient the model predictions can be made to agree with the measurements at essentially all times during the studied period. The model can account also for the observed hysteresis effects between cosmic rays of different rigidities.

Description: Measurement of the ratios of nuclear abundances H/He, CNO/Fe-group and the Fe-group/HE for 51 passages of Corotating Interaction Regions (CIRs) at 1 AU, and measurement of these ratios from 620 solar flares in the energy range 0.6 to 4 MeV per nucleon, show that CIR shock acceleration alone does not change significantly these ratios from the values they have for solar system abundances or the solar wind. The solar flare ratios continue to reflect strong biases in the abundances, consistent with requirements for multistage acceleration rpocesses at the Sun.

Description: Mission planning by NASA and ESA for the 1980 timeframe to observe the sun from an angle other than the solar ecliptic plane is discussed. Such missions will aid in a more thorough understanding of the sun, interplanetary space, and their influence on the earth. Jupiter swing-by techniques (first achieved by Pioneer 10) are proposed as a means of achieving an out-of-the-ecliptic mission for solar studies. Spacecraft trajectories are illustrated for a dual Pioneer spacecraft mission to observe the sun.

Description: The anomalous He-4 component, hereafter He(A), was first observed in the galactic cosmic-ray helium spectrum at energies below about 60 MeV per nucleon in 1972 at the beginning of the extended period of minimum solar modulation, 1972-1977, after which period it again disappeared as solar modulation increased in the new solar activity cycle. This component was not apparent during the 1965 solar minimum. It is found that the helium spectrum measured during a short interval of enhanced modulation in 1974-1975 shows the same level as the He spectrum measured during 1965. This fact demonstrates that the absence of He(A) in 1965 can be explained as the consequence of a greater level of solar modulation at low energies in 1965 than in most of the 1972-1977 solar minimum. It is concluded that He(A) may be present at all times in the outer heliosphere and be observable at successive solar minima if the residual solar modulation is sufficiently low, as in most of the 1972-1977 minimum.

Description: The anomalous nuclear component is neither of solar nor galactic cosmic ray origin. Its presence in the heliosphere is an independent probe for both interplanetary electrodynamical investigations--especially solar modulation--and probably the most direct means for determining the elemental and isotopic composition of those neutral atoms in the local interstellar medium that have high first ionization potentials (e.g., He, N, O, Ne, Ar, etc.). This report is a brief account of the evolution of our knowledge of this component for readers not specializing in the subject. Included are the initial discoveries of the component, its composition, spectra, heliospheric radial and latitudinal intensity gradients, modulation over the approximately 22 year solar magnetic cycle, trapping in the magnetosphere and its use for estimating the location of a heliospheric termination shock. Recent measurements from the ULYSSES spacecraft have provided conclusive evidence that incoming neutral atoms, after photoionization by solar uv, are picked up by the solar wind, thus lending support for the concept that after their acceleration--probably at a termination shock--they return to the inner heliosphere as pseudo-cosmic rays. ULYSSES spacecraft investigations extending to approximately 56 deg south latitude reveal, for both the anomalous nuclear component and the galactic cosmic rays, that there is a surprisingly small latitudinal intensity gradient. Thus, for the current phase of the solar cycle, modulation is much more spherically symmetric in the inner solar system than had generally been believed. A further surprise is the continual presence of approximately 26 day recurrent modulation at hight latitudes, without corresponding magnetic field compressions. These results are changing our ideas and requiring modification of our models for solar modulation in three dimensions.