Collisionless Shocks in the Heliosphere: A Tutorial Review

Published by the American Geophysical Union as part of the Geophysical Monograph Series.

Collisionless shocks are interesting and important for numerous reasons. Collisionless shocks are the simplest configuration in which a macroscopic flow is regulated by microscopic dissipation, a problem common to many different plasma processes. Collisionless shocks are therefore of basic plasma physical interest. There are also many important ways in which shocks affect the near-earth environment. Coronal shocks are believed to be responsible for the acceleration of solar flare energetic particles, which then propagate outward to fill the heliosphere. Shock propagation into the outer heliosphere may be a principal cause of the solar cycle dependent cosmic ray modulation. Interplanetary shock interactions with the earth's magnetosphere cause magnetic storms, intense low-latitude aurorae, and radio blackouts. Recent observations of fields and particles near interplanetary shocks and upstream of the earth's bow shock allow us to study particle acceleration processes in situ, giving us first-hand knowledge of processes which are occurring not only in our heliosphere but which may give us important insights into plasma processes which are occurring near distant interstellar shocks, processes which are believed to create cosmic rays.