PARTICLE-ACCELERATION IN GEOSPACE AND ITS ASSOCIATION WITH SOLAR EVENTS

Particle acceleration is a prominent feature of the geomagnetic storm, which is the prime dynamic process in Geospace - the near-Earth space environment. Magnetic storms have their origin in solar events, which are transient disturbances of the solar atmosphere and radiation that propagates as variations of the solar wind fields and particles throu gh interplanetary space to the Earth's orbit. During magnetic storms, ions of both solar wind origin and terrestrial origin are accelerated and form an energetic ring current in the inner magnetosphere. This cu rrent has global geomagnetic effects, which have both physical and tec hnical implications. Recently, it has been shown that large magnetic s torms, which exhibit an unusually energized ionospheric plasma compone nt, are closely associated with coronal mass ejections (CMEs). This im plies a cause/effect chain connecting solar events through CMEs and th e solar wind with the acceleration of terrestrial ion populations whic h eventually constitute the main source of global geomagnetic disturba nces. Here we present spacecraft observations related to storm-time pa rticle acceleration and assess the observations within the framework o f causes and effects of solar-terrestrial relationships.