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Abstract. An earth-directed coronal mass ejection (CME) was observed on May 12, 1997 by the SOHO Extreme ultraviolet Imaging Telescope (EIT). The CME, originating north of the central solar meridian, was later observed by the Large Angle Spectrometric Coronagraph (LASCO) as a "halo" CME: a bright expanding ring centered about the occulting disk. Beginning at about 04:35 UT, EIT recorded several CME signatures, including dimming regions close to the eruption, post-eruption arcade formation, and a bright wavefront propagating quasi-radially from the source region. Each of these phenomena appear to be associated with the same eruption, and the onset time of these features corresponds with the estimated onset time observed in LASCO. We discuss the correspondence of these features as observed by EIT with the structure of the CME in the LASCO data.

On 1996 March 7, the Solar and Heliospheric Observatory spacecraft conducted a multi-instrument campaign to observe polar plumes in the south polar coronal hole. Recent time-domain analyses of EUV Imaging Telescope images from that campaign show filamentary substructure in the plumes, on a length scale of ∼5Љ, which changes on timescales of a few minutes, and coherent quasi-periodic perturbations in the brightness of Fe ix and Fe x line emission at 171 Å from the plumes. The perturbations amount to 10%-20% of the plumes' overall intensity and propagate outward at 75-150 km s Ϫ1 , taking the form of wave trains with periods of 10-15 minutes and envelopes of several cycles. We conclude that the perturbations are compressive waves (such as sound waves or slow-mode magnetosonic waves) propagating along the plumes. Assuming that the waves are sonic yields a mechanical energy flux of 150-400 W m Ϫ2 (1.5-ergs cm Ϫ2 s Ϫ1 ) in the plumes.

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