Observing coronal mass ejections without coronagraphs

A coronal mass ejection (CME), strictly speaking, is a phenomenon observed via a white-light coronal imager. In addition to coronagraphs, a wide variety of other instruments provide independent observations of CMEs, in regimes ranging from the chromosphere to interplanetary space. In this paper we list the most important of these noncoronagraphic signatures, many of which had been known even before CMEs were first identified in coronagraph observations about 30 years ago. We summarize the new aspects of CMEs discovered in the past several years, primarily with instruments on the Yohkoh and SOHO satellites. We emphasize the need for detailed statistically based comparisons between SOHO CMEs and their noncoronagraphic manifestations. We discuss how the various aspects of CMEs fit into the current standard model sigmoids, flux rope, double dimming, arcade). While a class of CMEs follows this pattern, it does not appear to work for all events. In particular, some CMEs involve extended dimming regions and erupting transequatorial X-ray loops, indicating a more complex geometry than a simple bipolar magnetic configuration.