Low-Energy Cosmic Rays in Interplanetary Space

Abstract

The report presents the data of measurements of low-energy cosmic rays (mainly protons with energies E _p ≈ 1–5 MeV and E _p>30 MeV) from Zond-3 and Venus−2, −3, −4, −5, and −6 space probes for the period 1965–69. During this period the frequency of occurrence, duration, and intensity of the solar cosmic ray flares increased. Various spatial forms of the solar cosmic ray increase were found and studied. It has been shown from observations of solar cosmic rays injected by solar flares in 1965–67 that the low-energy protons propagate from the Sun in two ways: (1) rapidly, by means of particle movement along the magnetic force lines, and (2) slowly, by means of particle transfer in the layer corresponding to the falling phase of the Forbush-decrease, i.e. between the shock wave-front and the front of the hot plasma ejected by a flare. Reflection of particles from some ‘mirror’ region and considerable deceleration of shock waves were found in the first and second cases, respectively. It has been shown from the results of comparison of the galactic cosmic-ray decreases with active regions on the Sun that the amplitude of the decrease is determined by the dynamics of active regions, by their latitude, and their phase of development. Characteristic features of the results of 1969 include: the presence of very large and enduring proton fluxes with E _p>30 MeV observed following the shockwave fronts, a harder spectrum, and complex increases caused by groups of powerful solar flares. Considerable depth and rapid intensity-recovery are features of Forbush decreases in this period while the study of mean velocities of shock wave propagation indicates a pronounced direction of flare ejections and sustained pushing of shock waves by flare gases.