Space Science Reviews ??, ???−???, 2009
© Springer Science+Business Media B.V
Interplanetary coronal mass ejections observed in the heliosphere:
1. Review of theory
T.A. Howard
Air Force Research Lab., National Solar Observatory, Sunspot, NM 88349
Dep. of Space Studies, Southwest Research Institute, Boulder, CO 80302
S.J. Tappin
Air Force Research Lab., National Solar Observatory, Sunspot, NM 88349
Abstract
With the recent advancements in interplanetary coronal mass ejection (ICME)
imaging it is necessary to understand how heliospheric images may be
interpreted, particularly at large elongation angles. Of crucial importance
is how the current methods used for coronal mass ejection measurement in
coronagraph images must be changed to account for the large elongations
involved in the heliosphere. In this review of theory we build up a picture
of ICME appearance and evolution at large elongations in terms of how it would
appear to an observer near 1 AU from the Sun. We begin by revisiting the basics
of Thomson scattering describing how ICMEs are detected, in this we attempt to
clarify a number of common misconceptions. We then build up from a single
electron to an integrated line of sight, consider the ICME as a collection of
lines of sight and describe how a map of ICME appearance may be developed
based on its appearance relative to each line of sight. Finally, we discuss
how the topology of the ICME affects its observed geometry and kinematic
properties, particularly at large elongations. This review is the first of a
three-part series of papers, where a review of theory is presented here and
a model is developed and used in subsequent papers.