Solar Cosmic Rays of February, 1956 and Their Propagation through Interplanetary Space
- 1 November 1956
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 104 (3), 768-783
- https://doi.org/10.1103/physrev.104.768
Abstract
The data from six neutron-intensity monitors distributed over a wide range of geomagnetic latitudes have been used to study the large and temporary increase of cosmic-ray intensity which occurred on February 23, 1956, in association with a solar flare. During the period of enhanced intensity a balloon-borne neutron detector measured the absorption mean free path and intensity of the flare particles at high altitudes. From these experiments the primary particle intensity spectrum as a function of particle rigidity, over the range 15-30 Bv rigidity, has been deduced for different times during the period of enhanced intensity. It is shown that the region between the sun and the earth should be free of magnetic fields greater than ∼ gauss and that the incoming radiation was practically isotropic for more than 16 hours following maximum flare particle intensity. The decline of particle intensity as a function of time depends upon the power law , except for high-energy particles and late times, where the time dependence approaches an exponential. The experiments lead to a model for the inner solar system which requires a field-free cavity of radius greater than the sun-earth distance enclosed by a continuous barrier region of irregular magnetic fields [ gauss] through which the cosmic-ray particles must diffuse to reach interstellar space. This barrier is also invoked to scatter flare particles back into the field-free cavity and to determine the rate of declining intensity observed at the earth. The diffusion mechanism is strongly supported by the fact that the time dependence represents a special solution of the diffusion equation under initial and boundary conditions required by experimental evidence. The coefficient of diffusion, the magnitude of the magnetic field regions, the dimensions of the barrier and cavity, and the total kinetic energy of the high-energy solar injected particles have been estimated for this model. Recent studies of interplanetary space indicate that the conditions suggested by the experiments may be established from time to time in the solar system. The extension of the model to the explanation of earlier cosmic-ray flare observations appears to be satisfactory.
Keywords
This publication has 20 references indexed in Scilit:
- Notizen: Die Beobachtung der Ultrastrahlungseruption vom 23. Februar 1956 in Freiburg i. Brg.Zeitschrift für Naturforschung A, 1956
- Large increase of cosmic-ray intensity following solar flare on February 23, 1956Journal of Geophysical Research, 1956
- Solar Origin of Cosmic-Ray Time VariationsPhysical Review B, 1956
- Interplanetary Magnetic Fields and Cosmic RaysPhysical Review B, 1955
- The Sun's Magnetic Field, 1952-1954.The Astrophysical Journal, 1955
- Magnetic Fields in Spiral Arms.The Astrophysical Journal, 1953
- Cosmic Radiation Intensity-Time Variations and Their Origin. I. Neutron Intensity Variation Method and Meteorological FactorsPhysical Review B, 1953
- Neutrons Produced in the Atmosphere by the Cosmic RadiationsPhysical Review B, 1951
- Ultrastrahlung von der SonneZeitschrift für Naturforschung A, 1948
- Three Unusual Cosmic-Ray Increases Possibly Due to Charged Particles from the SunPhysical Review B, 1946