TABLE OF CONTENTS D. Boscher
The natural space environment in the solar system has several components (Hargreaves 1992; Suess and Tsurutani 1998):
Meteoroids, created in the early solar system. They reach the vicinity of the Sun with nearly a constant flux that is, however, significantly intensified during known meteor showers (e.g., Leonids).
Cosmic rays, charged particles with high energy. These originate from both inside and outside the galaxy. Moreover, so-called anomalous cosmic rays are produced by the interaction between the interstellar neutrals and the heliosphere.
Solar energetic particles escaping sporadically from the Sun. Nearly all elements are found but with an abundance and charge state different in cosmic rays.
Neutrons ejected by the Sun. These neutrons decay rapidly in the interplanetary medium and only a few of them remain in the Earth vicinity (but they can be much more abundant near the Sun).
Photons, from the ? rays to the radio frequency, coming essentially from the Sun. The maximum of the spectrum is in the visible, but the UV rays have a great influence on the near-ground environment of planets and moons.
The solar wind, consisting of plasma and magnetic field, originating in the Sun. At low heliospheric latitudes its density is high but its mean velocity is about 400 km/s with sporadic effects of coronal mass ejections; at high latitudes, as it comes from coronal holes, its velocity is higher (800 km/s) but its...
